Polytek Polytek Selecting proper mold making and casting

Document Sample
Polytek Polytek Selecting proper mold making and casting Powered By Docstoc
					              1    Mold Making Methods
Mold Making




                             GETTING STARTED
 Methods




                                                                                   To have a successful mold making experience,
                                                                                   PLEASE ...
              When making a flexible mold of an object in order to cast
              reproductions, you are faced with many choices of mold making             Study. Read as much "how-to" literature as
              and casting materials and methods -- it can be bewildering at
              first glance. In order to succeed, you must consider many factors
                                                                                        possible.
              before you start a project. Here are a few things to think about:
                                                                                        Start Small. Make a small, simple mold and
                    What is the model made of?
                                                                                        casting before attempting an important
                    Does the shape of the model present mold making or
                    demolding challenges?
                                                                                        piece. Get a feel for the materials without
                    What will the casting be made of?
                                                                                        costly mistakes. Experiment with small Trial
                    How many castings do you envision making?
                                                                                        Units (see p. 65).
                    How much money do you plan to spend?                                Ask Questions. It’s difficult to tell you how
                    How much time do you have to complete the project?                  to make molds and castings over the phone,
              Think ahead. You need to plan your project from start to finish           but we’ll try! Please call Polytek Customer
              before you begin. Read the “Methods” sections entirely so that
              you understand all of the factors that need to be considered              Service with questions.
              during the planning stage of your project.


                                                                                   Each mold making and casting compound is unique and may
              MOLD MAKING & CASTING MATERIALS                                      require special handling that differs from similar products.
                                                                                   Spend time learning the special requirements of every new
              Polytek Development Corp. produces nearly all types of flexible      product and making a small test mix before using the product on
              mold materials commonly used today as well as many casting           a larger scale to avoid loss of valuable time and materials.
              materials. Before beginning a mold making project, you must
              understand the advantages and disadvantages of various mold          Mold making and casting materials must be selected con-
              making and casting materials. At the same time, you must             currently. This is because some casting resins work well only in
              consider the type of mold you envision, because that too will        certain mold materials (and vice versa). If you have a specific
              play a factor in selecting appropriate mold making and casting       casting material in mind, then you select a mold material that
              materials. For information about types of flexible molds, refer to   works well with that casting material. Most often you can find
              pp. 7-9.                                                             mold and casting materials that work well together and satisfy
                                                                                   all of of your project requirements. The illustration below helps
              Flexible mold materials range from simple, one-part latex (the       to demonstrate this point.
              natural product of the rubber tree), Hydrogel® N (alginate, a
              powder to which water is added), and Skin-Wax (which is
              melted for use), to the higher performance two-part polyurethane      Casting                        Mold Material
              and silicone mold rubbers. Polytek’s two-part systems consist of      Wax                            All (except Skin-Wax)
              two liquids that after mixing together react to form rubber. These
              systems cure at room temperature and, therefore, are are referred
                                                                                    Concrete                       Polyurethane
              to as room temperature vulcanizing (RTV).
                                                                                    Plaster                        All (usually polyurethane)

                                                                                    Epoxy                          Polyurethane or silicone
                Selecting proper mold making
                                                                                    Polyurethane                   Silicone or polyurethane
               and casting materials for the job
                                                                                    Polyester                      Silicone or polyurethane
                  at hand is the 1st step to
                                                                                    Acrylic                        Silicone or polyurethane
                          success!
                                                                                    Metal (low-melting)            Silicone



      2
              Polytek          ®


              Development Corp.                                                                                     (610)559-8620 • (800)858-5990
                                                                                              Mold Making Methods                    1




                                                                                                                                         Mold Making
SELECTING A MOLD MAKING MATERIAL




                                                                                                                                          Methods
                                                                          One-part mold materials usually
To select the best mold making material for your project,
consider several factors: model composition, shape and size;             present more disadvantages than
mold type; cost; and timing. First, familiarize yourself with the
common types of flexible mold making materials and the                         two-part materials.
advantages and disadvantages of each. After you have learned
about the various mold materials, take into account the                Polytek’s two-part materials are
characteristics of your model and the mold making challenges it
presents.
                                                                       tough, long-lasting, easy-to-use
Review the tables below.                                                         mold rubbers.
One-Part Mold Compounds
 Type                         Advantages                   Disadvantages                         Uses                     Methods
 Polytek Products

 Alginate
 Hydrogel® N                  Safe for body contact        Very limited life; dries out          Body molds               Pour
                                                           Gets model wet                        Single-use molds         Layup

 Wax                          Safe for body contact
 Poly Skin Wax                Low cost                     Low strength                          Body molds               Brush-on
                              Fast set                     Limited use                           Single-use molds         Dip
                              Remeltable                   Must melt prior to use

 Latex
 Poly Latex 60                High strength                Not dimensionally stable              Concrete                 Brush-on
 Poly Latex False Face                                     Takes days/weeks to make mold         Plaster statuary         Spray
                                                           Oils can soften and destroy molds     Limited resins           Dip
                                                           Blanket molds only (shell required)


Two-Part Mold Rubbers
 Type                         Advantages                   Disadvantages                         Uses                     Methods
 Polytek Products

 Polyurethanes
 Poly 74, 75, and 77 Series   Moderate to low cost         Requires careful release agent        All materials            Pour
 Poly 81 Series               Good strength                May be moisture sensitive             (except molten metals)   Brush-on
 Poly 72-40 Series            Many versatile varieties                                                                    Spray
 Polygel®                     Non-shrink available

 Tin Silicones
 TinSil® 70 Series            No release agent needed       Higher cost                          All materials            Pour
                              High strength                 Shrinks up to 1% on curing           (especially resins and   Brush-on
                              Excellent chemical resistance Limited cured storage life           low melting metals)

 Platinum Silicones
 PlatSil® 71 Series           No release agent needed       Higher cost                          All materials            Pour
 PlatSil® 73 Series           No shrink on cure             Cure inhibited by some surfaces                               Brush-on
                              Good cured storage life
                              High strength
                              Excellent chemical resistance


                                                                                                                     Polytek         ®

                                                                                                                                         3
www.polytek.com                                                                                                      Development Corp.
              1    Mold Making Methods
Mold Making




              Model Composition
                                                                                     $    Cost per cubic inch is your real cost --
 Methods




              A model’s composition or surface coating may restrict you to
              certain mold making materials. Certain mold materials do not                price per pound can be misleading.
              cure properly over some model materials (i.e., platinum-cured          When using mold making or casing materials you are usually
              silicones do not cure on sulfur-containing clay models).               filling a given space. The lower the cost per cubic inch of
              Sometimes, if the model’s composition presents a problem, it           material the lower the cost of filling the space. “Specific
              can be overcome by carefully sealing the model (see p. 11).            Volume,” expressed in cubic inches per pound (in3/lb), is the
              Thoroughly review product technical bulletins to be sure that          key to calculating the real cost of a mold making and casting
              there are no compatibility issues between your model and the           material.
              mold material you’ve selected. If your model is delicate or
                                                                                     Some rubbers and plastics that have a low price per pound
              valuable, it is best to try the selected mold material on a small
                                                                                     contain dense fillers such as powdered marble or silica. These
              hidden area before you jump into mold making. Fragile models
                                                                                     fillers typically reduce the price per pound, but raise the price
              can be damaged in the mold making process. The resulting
                                                                                     per cubic inch. Simple calculations reveal the real cost of your
              mold, however, can be used to make a reproduction out of a
                                                                                     material in terms of cents per cubic inch.
              more durable material. [Note: If the model is a human body,
              there are obvious safety issues. Consider Hydrogel Mold                Poly 74 Series Rubbers (see p. 34) are low density and
              Compound or Poly Skin Wax (see pp. 59-60).]                            contain no heavy fillers. They yield 27.5 in3/lb. Poly-Fast 72-
                                                                                     40, a 724-type rubber, contains fillers and yields only 20
              Model Shape and Size                                                   in3/lb -- nearly 1/3 less rubber volume per pound!
              The size, shape, and even location of your model may limit you         For example:
              to certain mold making materials and types of molds (i.e., a               An 80-lb unit of Poly 74-30 costs $318 or $3.98/lb ($318/
              model with deep undercuts does not lend itself to a simple box             80 lb). Dividing $3.98/lb by 27.5 in3/lb yields a cost of
              mold). If you are restricted to a certain type of mold, then your          $0.14 per in3.
              choices of mold materials may be limited.
                                                                                         A 49.5-lb unit of Poly-Fast 72-40 costs $185 or $3.74/lb
              Cost                                                                       ($185/49.5 lb). Dividing $3.74/lb by 20 in3/lb yields a
              Both the volume of material needed and the price per unit                  cost of $0.19 per in3.
              volume must be considered in calculating project cost. The                      Poly 74-30 = $0.14 per in3
              quantity of mold making material needed is dictated largely by                  Poly-Fast 72-40 = $0.19 per in3
              the type of mold you choose to make -- a large model may
              mandate a brush-on mold since any other type of mold would             At first glance it appears that Poly 74-30 is the more
              require too much material. The quantity of material needed can         expensive product; however, to fill a given space, using Poly
              be calculated by estimating the volume of mold making material         74-30 actually costs nearly 30% less than higher density
              needed (in cubic inches) and dividing by the specific volume           Poly-Fast 72-40 rubber.
              (cubic inches per pound) of the material (see box to the right).
              To determine project costs more accurately, one also needs to
              consider the time it takes to make the mold (see below).

              Time Considerations
              Timing plays an important role in the selection of a mold
              making material. With some materials a mold can be completed
              in an afternoon (i.e., accelerated silicone and polyurethane mold
              rubbers), while with others, it can take weeks (i.e., latex rubber).
              To learn more about demold times, read the technical bulletins
              for individual products. Remember, the fastest material or
              method may not be the least expensive.
              Consider how long you intend to use and keep the mold. Some
              materials are only suitable for one casting (i.e., Hydrogel), while
              others will hold up for hundreds of castings (silicones and most
              polyurethanes). Also, consider “library life:” how long you
              expect the mold to remain useful after sitting on a shelf. Most
              properly cured rubber molds are useable for many years, but
              some degrade within 2 to 4 years (i.e., Poly 72-40 and TinSil
              rubbers). For molds with long library life, use polyurethane
              rubbers (except Poly 72-40) or PlatSil silicone rubbers.


      4
              Polytek           ®


              Development Corp.                                                                                       (610)559-8620 • (800)858-5990
                                                                                                Mold Making Methods                     1




                                                                                                                                              Mold Making
SELECTING A CASTING MATERIAL                                              Mold Material                Casting Material




                                                                                                                                               Methods
To select the best casting material for your project, you must
                                                                          Skin-Wax                     Low-exotherm materials --
consider several factors: mold composition and construction,
required characteristics of the casting (i.e., weight, durability),                                    polyurethane and silicone
cost, and timing.                                                                                      rubbers and select resins
First, it is a good idea to familiarize yourself with the common          Hydrogel                     Materials that are not moisture
casting materials and understand the general advantages and                                            sensitive -- wax, plaster,
disadvantages of each. The most common and least expensive                                             silicones and select resins
casting materials are gypsum plasters and cements, both of
which are available in many formulas for various end uses.                Latex                        Cement, plaster and select
Waxes are castable, of course, but uses are limited by low                                             resins
hardness and high shrinkage. Low melting metals can be cast in            Polyurethanes                Most casting materials are
heat resistant silicone molds. Epoxy and polyurethane systems
                                                                                                       acceptable, except metals
are versatile and durable casting materials. Polyester resin is
quite low in cost, especially if low cost fillers like sand,              Silicones                    All casting materials are
limestone or wood flour are added.                                                                     acceptable
The table below presents common casting materials suitable for
use in molds made from Polytek flexible mold products.
                                                                         Molds made from Polytek products are non-porous and casting
Mold Composition                                                         materials used in the molds should "cure" or set chemically. In
A mold’s composition may restrict you to certain casting                 most cases, air drying materials are not suitable since the rubber
materials. In a few cases, casting materials may rapidly degrade         prevents them from drying except from the back. Water clay,
or even destroy the mold (i.e., exothermic epoxy resins will melt        paper-mache, and latex are often not suitable casting materials.
a wax mold). Carefully review product technical bulletins to be          The illustration above provides a general guideline regarding
sure that there are no compatibility issues between your mold            suitability of casting materials depending on mold composition.
and the casting material.



 Casting Material                    Advantages                       Disadvantages                     End Uses
 Wax                                 Easy demold                      Fragile                           Foundries
                                                                      High shrinkage                    Candles
                                                                                                        Resculpting
 Vinyl                               One-part liquid                  Requires heat to use              Prototypes
                                                                                                        Parts
 Gypsum Plaster                      Fast                             Indoors only                      Most indoor objects
                                     Yields good quality              Brittle
 Cement                              Acceptable for outdoor use       Heavy                             Statuary (indoor and outdoor)
 Specialty Cement                                                     Rough surface                     Architectural ornaments
                                                                      Slow set
 Design Cast and Forton® MG          Outdoor use ok                   Higher cost
 Acrylic Resin                                                        Expensive                         Many diverse uses
                                                                      Difficult to use                  (Painting may be needed for
                                                                      Strong odor                       outdoor use.)
 Polyester Resin                     Inexpensive                      Flammable
                                                                      Strong odor
 Epoxy Resin                         Moderate price                   Health hazards
                                                                      Limited mass
 Polyurethane Resin                  Moderate price                   Moisture sensitive
                                     Easy-to-use



                                                                                                                        Polytek           ®

                                                                                                                                              5
www.polytek.com                                                                                                         Development Corp.
              1       Mold Making Methods
Mold Making




              Weight of the Casting                                                 “Exotherm” of Casting Material
 Methods




              Casting materials have different densities that affect the weight
                                                                                    Exotherm is the heat of reaction produced as a resin or rubber
              and feel of the final casting. For example, plaster and cement are
                                                                                    cures. Polyurethane rubbers generally have very little
              heavy, while resins are lighter. The weight of a casting can often
                                                                                    measurable exotherm. Poly 74-55 in a large mass may rise
              be controlled by adding fillers to the casting material. Also, you
                                                                                    just a few degrees above the temperature of the Parts A and B
              can create a lighter, hollow casting, by using a "plug" to prevent
                                                                                    before mixing. Epoxies, on the other hand, are much more
              casting material from filling the entire mold, or by laying up into
                                                                                    exothermic and, if poured in too large a mass for the heat to
              or rotating a mold so casting material cures in a thin shell on the
                                                                                    dissipate, may get so hot that they boil and burst into flames.
              mold surface. These techniques are discussed on p. 10.
                                                                                    Therefore, casting epoxies in large masses is dangerous and
                                                                                    must be avoided.
              Exterior Durability of the Casting
                                                                                    Consider exothermic heat when selecting casting resins. If the
              Materials such as cement are fine for both indoor and outdoor
                                                                                    casting is so thin that exothermic heat is easily dissipated into
              environments, whereas most other casting materials need to be
                                                                                    the mold, the resin will be slow to cure, but there will be no
              painted or sealed for outdoor use. Exterior castings are subject to
                                                                                    thermal shrinkage caused by gelling while hot then cooling.
              elements such as UV light from the sun, rain, and freezing and
                                                                                    Slow curing in these cases can be overcome by using warm
              thawing. Cement and polyester resin castings are fine for interior
                                                                                    molds or using a faster curing system. Massive castings tend
              and exterior uses. Polyurethanes, however, must be painted or
                                                                                    to build heat in the center of thicker sections and sometimes
              sealed prior to being placed outdoors in order to avoid yellowing
                                                                                    thinner sections of the same casting remain cooler. If the
              and chalking of the bare plastic, which occurs over time. Fillers,
                                                                                    temperature difference is too great, distorted parts or shrink
              pigments and Poly UV Additive can be added to improve
                                                                                    marks may be evident. Often, warm molds can help overcome
              exterior performance (see p. 61 for information on Poly UV
                                                                                    this problem as can addition of fillers or use of slower curing
              Additive).
                                                                                    systems. High curing temperatures shorten rubber mold life,
              Cost                                                                  so proper selection of casting systems results in best economy
                                                                                    and longest mold life.
              Both the quantity of material needed and the price per cubic inch
              must be considered in calculating project cost. The
              quantity/weight of casting material needed is dictated by the         To reduce costs and cast larger masses,
              volume of material needed (in cubic inches) divided by the
              specific volume (cubic inches per pound) of the casting material.     ADD FILLERS to polyurethanes & epoxies.
              Here is a general idea about the relative costs of casting            Many fillers are suitable to add to liquid plastics to reduce
              materials.                                                            costs and help dissipate exotherm, which can cause shrinkage
                                                                                    and limit the size of the mass that can be cast at once. Heavy
                       High Cost         Unfilled polyurethanes and epoxies
                                                                                    fillers absorb more exothermic heat, but result in a heavy
              COST




                       Medium Cost       Filled resins, speciality cements (i.e.,   casting. Lightweight fillers can make the casting lighter than
                                         Forton® MG)                                wood so it will float and carve easily. Some fillers such as
                       Low Cost          Cement, plaster, wax, filled polyester     wood powder and nut shell flours may contain moisture and
                                                                                    cause foaming of the plastic or other problems. Dry fillers that
              Obviously, to determine true project cost one needs to consider       stir easily into the mixed resin are best. The cost per cubic
              the time it takes to make the casting (see below).                    inch of resin displaced is the real cost of these fillers. For
                                                                                    example, some typical costs per cubic inch follow:
              Time Considerations                                                   Filler                       $/lb      Density (g/cc)    $/in3
              Timing plays an important role in the selection of casting            Dry Sand                    $0.05         2.75           0.005
              material. With some materials, a finished casting can be made in
                                                                                    Bronze Powder                5.00         8.85           1.590
              minutes (i.e., EasyFlo 60 Plastic); while with others, it can take
              days (i.e., cement). The fastest material or method often is not      Ground Limestone             0.15         2.70           0.015
              the least expensive.                                                  Extendospheres CG            0.50         0.70           0.013
                       Slow              Cement                                     Q-Cel 2116 or 3M C/15        6.00         0.10           0.022
               TIME




                       Medium            Plaster, wax, thin resins                  Poly Plastics                3.75           1.10         0.140

                       Fast              Polyurethane and polyester resins          Adding an equal volume of low cost filler to a Poly Plastic
                                                                                    can cut the cost of the casting nearly in half! For example, one
                                                                                    cubic inch of resin at $0.14 plus an equal volume of filler at
                                                                                    $0.015 yields approximately two cubic inches costing $0.155
                                                                                    or about $0.07 per cubic inch for the mix.


      6
              Polytek          ®


              Development Corp.                                                                                      (610)559-8620 • (800)858-5990
                                                                                                 Mold Making Methods                1




                                                                                                                                             Mold Making
       TYPES OF FLEXIBLE MOLDS




                                                                                                                                              Methods
There are two basic types of flexible rubber molds: block molds
and blanket molds. Within these two basic types, there are
numerous variations differing in both construction and
complexity.

BLOCK MOLDS
Block molds are typically made by placing the model into a
containment area (i.e., mold box) and pouring liquid rubber over
the model. After curing, the rubber is removed from the model
and the result is a single-piece, poured block mold. This is the
simplest type of mold. Single-piece, poured block molds are best
for models with a relatively flat base or back and no sharp
undercuts that prevent the rubber from demolding from the
                                                                      Various molds and castings of ornate architectural elements
model. This type of mold would be used for reproduction of a
                                                                      and decor.
wall plaque.
For a model with undercuts (i.e., the chin of a cherub’s face) a      Poured mold materials generally pick up detail with fewer
softer rubber can be used or the mold may need to be cut to           entrapped air bubbles than materials that are applied by brush or
allow for removal of the model and castings: this is referred to as   spray, except where bubbles on the surface of the rising liquid
a split block mold. In some cases, the block mold may need to be      are trapped under a ledge such as under the chin of a head
cut into or poured in several pieces to allow for removal of the      model. Tilting the mold box while pouring is a useful technique
model and then carefully reassembled prior to casting: this is        for preventing air entrapment. If this does not help, a brush-on
referred to as a multi-piece block mold.                              mold, or pouring one section at a time may be advised.
Sometimes, multi-piece block molds are made in sections, by           For diagrams depicting the procedures to make a single-piece
pouring on one surface at a time, allowing to cure, then pouring      poured block mold, a split single-piece poured block mold, and
on the adjoining surface against the previous pour. This              a multi-piece poured block mold, see pp. 17-18.
technique is necessary when the model has details on all sides        A note on the terminology: Since a block mold is often made in
(i.e., does not have a flat base or back).                            box shape, it is sometimes called a box mold. However, this type
Poured molds are sometimes free standing if the rubber is thick       of mold can be made in any appropriate containment area (i.e., a
enough to hold its shape, but often the box or rigid shell is used    cylinder such as a piece of PVC pipe). Also, block molds are
with the mold to maintain the desired shape. Generally, the box       sometimes referred to as poured molds since this is the method
or shell (“mother mold”) must be separate from the rubber mold        used to make them.
in order to allow the mold to flex for removal of the model or
casting.


                                                                                          Mold Complexity

                                                                                     Multi-Piece Poured Blanket Mold      Contributing
                                                                                                                             Factors:
                                                                                     Poured Blanket Mold
                                                                                                                                  Size
                                                                        Complexity




                                                                                     Sprayed Blanket Mold                    Location
                                                                                     Brushed Blanket Mold                      Shape
                                                                                                                                 Time
                                                                                     Multi-Piece Block Mold
                                                                                                                             Materials
                                                                                     Single-Piece Block Mold


Two-piece block mold

                                                                                                                       Polytek           ®

                                                                                                                                             7
www.polytek.com                                                                                                        Development Corp.
              1     Mold Making Methods
Mold Making




              BLANKET MOLDS
 Methods




              As the name implies, blanket molds resemble a thin blanket
              carefully placed around the model. Blanket molds are made by
              either brushing or spraying the flexible mold material onto the
              model or pouring the mold material into a pre-constructed shell
              around the model. With a few mold materials (i.e, latex, wax), it
              is possible to make a blanket mold by dipping the model into the
              liquid material. Blanket molds are generally ¼- to ½-inch thick.
              To hold a blanket mold in its proper shape after the cured rubber
              is removed from the model and during the casting process, a
              rigid or firm mold shell (“mother mold”) is required.
              Blanket molds are often mandated by the size and/or location of
              the model. Since blanket molds consume far less rubber than a       One-piece, Polygel ® brushed blanket mold.
              conventional block mold, they are preferred for large or
              irregularly shaped models. Typically mold rubber is sprayed or      lock together to maintain position with respect to one another
              brushed on large models. Often, blanket molds are the only          and to the shell.
              choice for large, immovable models (i.e., large gargoyle high on    With the development of self-thickening and “thixotropic” (see
              a building facade).                                                 definition below) mold materials, making brush-on and sprayed
              With some models, blanket molds can be made in one piece and        blanket molds has become routine. Not only do brush-on and
              lifted or peeled off the model and subsequent castings like a       spray molds use less rubber, but they are generally faster to
              sock; this is sometimes called a “glove mold.” A bas relief or a    make than poured blanket molds and offer the moldmaker visual
              figure with a pyramid shape (the bottom wider than the top) lend    control of rubber placement.
              themselves to one-piece molds. Molds that are to be turned back     In the past, blanket molds were often made by dipping the model
              on themselves and peeled off must be kept thin, usually less than   into or brushing on latex. Since each layer of latex must dry
              1/8-inch thick, to minimize stress and possible tearing of the      overnight before the next layer can be applied, building up an
              rubber. As the mold is peeled off, it may need to be lubricated     adequate thickness of latex for a useable mold can take weeks.
              with silicone release or soapy water on the outside surface to      Trying to brush-on a pourable liquid without thickening usually
              allow it to slide easily against itself.                            produces less than satisfactory results since the the liquid flows
              For many types of models, the blanket mold must have a split        off vertical surfaces. In order to make molds faster, moldmakers
              down one side to allow for easy removal of the model and to         add fillers to pourable mold rubbers in order to thicken the
              reduce the chance of tearing the mold. The rubber at the end of     uncured mix to a consistency that can be applied by brush. For
              the seam may be reinforced with fabric at the top where a tear      example, Poly 74-30 Liquid Mold Rubber can be mixed with
              may be likely to develop in the mold.                               fumed silica (i.e, Cab-O-Sil®) to make brush-on blanket molds
                                                                                  (see photograph on p. 21). Many customers use this method
              For complex models, blanket molds can be made in two or more
                                                                                  because it allows them to thicken the rubber to the exact
              pieces. Shims or flanges are used to create seams or “parting
                                                                                  consistency that is desired and is the most economical method of
              lines” where required on blanket molds and their shells. A split
                                                                                  making brush-on molds. For more information regarding
              blanket mold can be made by affixing a thin shim of aluminum
                                                                                  thickening of liquid mold rubbers, refer to the product
              flashing, cardboard or stiff plastic film to the model projecting
                                                                                  descriptions (see pp. 34-45) or call Polytek Customer Service.
              several inches, applying release, and brushing/spraying the
              rubber up against the shim. The shim should have keys or            In 1992, Polytek received a patent for the Polygel® technology,
              indentations to allow the rubber flanges of each mold section to    which enables the mixed Parts A and B liquids to immediately
                                                                                  react to form a gel with a consistency perfect for brush-on
                                                                                  application. Polygel 35, 40 and 50 Liquid Mold Rubbers are
                                       THIXOTROPY:                                ideal for brushing on a properly prepared model right after Parts
                                                                                  A and B are mixed. In addition, certain Polygel products have
                    The key to successful brush-on molds.                         been specially formulated for spray application (Polygel Spray
                                                                                  35, Polygel Spray 50 and Quick Spray 50). See pp. 36-37 for
               Thix.ot.ro.py \thik-`so-tr -pe\ n [fr. Gk thixis
                                                        e
                                                                                  information on Polygel products.
               act of touching]: the property of various gels                     Whether using liquid rubber thickened with Cab-O-Sil or the
               becoming more fluid when disturbed (as by                          advanced Polygel products, a most important characteristic of
               mixing) -- thixotropic adj                                         the mixed mold material for brush-on or spray application is
                                                                                  “thixotropy” (see box). To make a brush-on or spray-on blanket
               (Webster’s Ninth New Collegiate Dictionary)
                                                                                  mold, the rubber must be thick enough to not sag after


      8
              Polytek              ®


              Development Corp.                                                                                     (610)559-8620 • (800)858-5990
                                                                                              Mold Making Methods                     1
                                                                       have projecting keys or




                                                                                                                                               Mold Making
                                                                                                                                                Methods
 Both brush-on and spray blanket                                       rubber “snaps,” on its flange
                                                                       and back so that the mold
                                                                       locks into the shell to
 molds are most easily made with                                       prevent flopping out of
                                                                       position. [Tip: Buttons of
                   ®
     Polygel Liquid Mold Rubbers.                                      rubber, cast in advance in
                                                                       plastic pill holders, can be
                                                                       bonded onto the last coat of
application on the model, but also must be more fluid when it is       the mold rubber so that the
mixed or moved around the model surface with a brush. Polygel          shell is formed around them
products are thixotropic: they are thick enough to resist sagging      holding the mold in position
when applied to a vertical surface, but are fluid when mixed and       in the shell.]
moved around the model surface. Basically, the more energy you         In the case of a poured
put into a thixotropic material, the lower the viscosity -- the        blanket mold, the mother
faster you stir it the more fluid it seems. A good liquid rubber for   mold is typically made
brush-on molds must become thixotropic shortly after Parts A           before the rubber mold is
and B are mixed together -- that’s Polygel.                            made. After the mother mold       Polygel® rubber mold and resin
For diagrams depicting the procedures to make a single-piece           is cured, it is positioned over   shell made of Poly 15-6 Liquid
blanket mold, a split single-piece blanket mold, and a multi-          the model and the liquid Plastic thickened with Poly Fiber.
piece blanket mold, see pp. 18-23.                                     mold rubber is poured into
                                                                       the void between the mother mold and model to make the
                                                                       blanket mold. For more on this technique, see pp. 22-23.
MOLD SHELLS (AKA “MOTHER MOLDS”)
                                                                       A mother mold can last indefinitely and can help prolong the life
A mold shell, also known as a “mother mold,” is not a
                                                                       of a mold since a rubber mold stored in its shell can maintain
production mold but rather a shell that is required to hold the
                                                                       exact dimensions. The mold in its shell will last many years if it
flexible rubber mold in its proper shape. The shell and mold are
                                                                       is stored in a cool, dry area out of sunlight. Still, when the
used on the production line. Mother molds are sometimes used
                                                                       rubber fails (as all flexible molds eventually do) the shell is
with block molds and are nearly always used with flexible
                                                                       simply repositioned over the model and a new mold is poured,
blanket molds. Mother molds can be made of plaster, plaster and
                                                                       ready for use the next day.
hemp, polyester resin and fiberglass, urethane foam, or one of
Polytek’s firm liquid rubbers or rigid liquid plastics. Poly 15
Series Liquid Plastics (15-6 and 1512X) and Polygel Plastic-75                                            These three photos
make tough, durable, lightweight mold shells in a matter of                                               illustrate the construction of
minutes! For more information on 15-Series Liquid Plastics see                                            a poured blanket mold.
p. 49; for Polygel Plastic-75, see p. 55.                                                                 First, the model, a gargoyle
                                                                                                          face, is covered with clay.
The mother mold is usually made over and is removable from
                                                                                                          Next, a rigid, plastic mold
the rubber production mold. Care must be taken so that a rigid
                                                                                                          shell (i.e., Poly 1512X, see
shell does not lock onto undercuts in the block or blanket mold.
All such undercuts must be eliminated or the shell must be made                                           p. 49) is constructed over
in multiple pieces to work around them. In certain situations, a                                          the clay blanket. After the
firm but flexible mother mold can offer a good solution to                                                plastic cures, it is removed
undercuts. A flexible mother mold, such as one made of Poly                                               and the clay is removed
74-30 Mold Rubber, can be pulled off simple undercuts. You                                                from the model. Then the
may use a little more rubber, but you can save lots of labor.                                             plastic shell is repositioned
                                                                                                          over the model and liquid
Mother molds are often two or more pieces even when the mold
is one piece. The shell for a split mold would part along the line                                        rubber (i.e., PlatSil® 71-15,
of the split in the mold. Parting lines for shells can be                                                 see p. 43) is poured through
established using plasticene strips applied to the cured rubber,                                          an opening in the shell and
building up the shell against one side of the strip, removing the                                         covers the model. Once the
strip, applying release and building the other half of the shell.                                         rubber cures, the model is
When complete, the sections of the shell press the flanges of the                                         removed and the mold is
rubber together like a gasket, keeping the parting line tight and                                         ready to use. Cast away!
inconspicuous. If a brush-on mold is large, the rubber should


                                                                                                                      Polytek              ®

                                                                                                                                               9
www.polytek.com                                                                                                       Development Corp.
              1    Mold Making Methods
Mold Making




                           TYPES OF CASTINGS
 Methods




              There are numerous types of castings and casting methods.
              Castings vary by the type of material that they are made of (see
              p. 2), and by the method employed to make them. The table
              below summarizes the most common casting methods along
              with the advantages and disadvantages inherent in each
              technique and the products for which one might use each
              method.
              The photo to the right shows numerous castings made from
              various Polytek casting plastics.




               Casting Method                                 Advantages             Disadvantages                   End Uses
               Solid Pour
                  Material is poured into the mold            Fast                   Heavy                           Small objects
                  resulting in a solid casting.                                      Possible high cost              Industrial tools

               Gel Coat and Layup
                  A thin surface coat is applied and          Lightweight            Time consuming                  Rigid molds
                  subsequent layers of reinforcing            Less material used                                     Mold shells
                  material like fiberglass mat and            High quality surface                                   Large objects
                  resin are built up to a thin, strong                                                               Bonded bronze
                  laminate.

               Slush Cast
                  Material is manually rotated in the         Lightweight            Time consuming                  Art objects
                  mold creating a thin layer resulting        Less material used                                     Bonded bronze
                  in a light-weight hollow casting.

               Rotational Cast
                                                              Fast                   Need a machine                  Larger statuary
                  A closed mold is rotated by
                  machine as a small amount of                Easy                                                   Hollow parts
                  material coats the surface and sets,        Lightweight
                  resulting in a hollow, light-weight         Six-sided parts
                  casting.

               Injection
                                                              Quality parts          Requires setup time             Manufactured parts
                  Liquid is forced into the mold
                  under pressure.                                                    Often need a machine


               Vacuum and Pressure
                  Bubbles are eliminated, resulting           Quality parts          Requires setup time             Prototypes
                  in perfect, high detail parts. Used                                Need vacuum pump/pressure pot   Figurines
                  in conjunction with solid pour.

               Direct Layup/Spray - No Mold
                  Material is spread over a screen            Lightweight            Time consuming                  Amusement/theme parks
                  armature. Surface detail is sculpted into   Less material used                                     Sculpted rocks
                  the wet material or plastic hardcoat
                  sprayed over carved foam substrate.




      10
              Polytek          ®


              Development Corp.                                                                                 (610)559-8620 • (800)858-5990
                                                                                        Mold Making Methods                   1




                                                                                                                                    Mold Making
      MOLD MAKING PROCEDURES




                                                                                                                                     Methods
                                                                     If you don’t follow directions ...
This section guides you from model preparation through               there is a lot that can go wrong ...
finishing your casting. The directions provided here are general
in order to be helpful regardless of what mold making and
casting materials you choose and what type of mold or casting
                                                                      •   Improper Mix Ratio - Slow, non-curing or
                                                                          soft material can result if two-part materials are
you’re making. The following sections are presented in the order
                                                                          not weighed or measured accurately. Always use
that your project should proceed. Diagrams that depict
                                                                          an accurate scale (see accessories, p. 63). Do
procedures for making a few different types of molds are
                                                                          calculations carefully and double check the mix
presented after the complete text description (see pp. 17-23).
                                                                          ratio listed on labels and product literature.
SAFETY FIRST!                                                         •   Release Agent or Sealer - Incorrectly
Before you even open your containers of mold making or                    applied or missing, or use of the wrong sealer or
casting materials, understand the hazards of the materials that           release can result is sticking or damage to the
you’ll be working with.                                                   mold/casting. If you’re not sure that you’ve
•   Read material safety data sheets (MSDSs) and product                  properly sealed/released a model, make a test
    labels - MSDSs are sent with every Polytek product and                cure. Too much release agent can cause pinhole
    contain very important safety information. Also, Polytek              surface defects or bubbles in the mold and/or
    product labels have hazard warnings and precautionary                 casting.
    statements. Read the MSDS and labels carefully so that you
    can use Polytek products safely. If you do not receive
                                                                      •   Low Temperatures or Demolding Too
    MSDSs with your shipment, call Polytek Customer Service
                                                                          Soon - Deformed parts can result. Fluctuating
                                                                          temperatures during curing can cause bubbles and
    and they will promptly get them to you.
                                                                          dimensional changes.
•   Understand health hazards - Some uncured Polytek
    products can cause skin, eye and respiratory irritation if        •   Leaking Mold, Boxes or Shells - Your pour
    improperly handled. Also, a few uncured products can                  can spill, wasting material and time. Use
    cause dermal and respiratory sensitization (i.e., allergic            mechanical fasteners and hold downs and be sure
    reactions) in sensitive individuals. Avoid skin and eye               that seams are tight and sealed.
    contact and breathing vapors from uncured materials. Do
    NOT use Polytek products where food or prolonged body             •   Material Hardens Before It’s In Place -
    contact may occur.                                                    Avoid delays once material is mixed. Watch a clock!
•   Use personal protective equipment (PPE) and                       •   Unmixed Material - Streaks of uncured or
    engineering controls - Follow recommendations on                      soft areas and/or gas bubbles can develop several
    product MSDSs for use of PPE such as gloves, dust masks,              weeks after curing if Parts A and B are not
    safety glasses or goggles, aprons, and, in limited cases, air-        thoroughly mixed. Poorly mixed material is often
    purifying respirators with organic vapor cartridges. Use              from the sides and bottom of the mixing container.
    products in areas with adequate ventilation such as a large
    open room with air circulation.                                   •   Incorrect Material Selected - Choosing
                                                                          the wrong material can result in sticking or
READ DIRECTIONS                                                           damage such as staining or softening a model,
All too often, projects are spoiled because, in enthusiasm for            mold or casting.
completing a project, important directions are not followed.
Before starting your project, read product technical bulletins and    •   Material Not Stirred Before Use - Some
label directions thoroughly. Call Polytek Customer Service if             components (Part A or B) must be stirred before
you have any questions.                                                   use. If the component is not carefully stirred
                                                                          before mixing with its counterpart, soft cures or
MODEL PREPARATION                                                         bubbles can result.
Porous models, such as wood, plaster, stone, pottery or               •   Contaminated Material - Moisture or
masonry, must be sealed, then coated with a release agent                 other foreign contaminants can spoil the cure of
such as Pol-Ease® 2300 Release Agent. Sealing prevents rubber             materials. Freshly opened containers and clean
or resin from penetrating pores in the model surface. Several             tools are important.
coats of paste wax, allowed to dry and polished or melted
paraffin, petroleum jelly, lacquer, shellac, paint, PVA (polyvinyl

                                                                                                              Polytek           ®

                                                                                                                                    11
www.polytek.com                                                                                               Development Corp.
              1    Mold Making Methods

                                                                                   alcohol solution), and potters’ soap on plaster all work well for
Mold Making




                                   Important Terms
 Methods




                                                                                   certain surfaces and mold rubber or resin combinations. Some
              Cure time is often longer than demold time, sometimes even           rubbers (i.e., Poly-Fast 72-40) contain materials that dissolve or
              though a product feels cured and can be demolded, curing may         soften lacquer and paints. For them, wax or shellac are often
              continue for up to a week.                                           used as sealers. Polyurethanes bond tenaciously to shellac,
              Demold time is the soonest a cured product can be removed            however, so if shellac is used as the sealer, release agent must be
              from the mold if it has been at recommended temperature.             very carefully applied over it.
              Demolding castings as soon as possible helps to extend mold
              life. Thin castings may require more time in the mold before         Bare plaster is best sealed with potters’ soap (or Murphy’s Oil
              demolding.                                                           Soap) lathered into the damp surface of the plaster with a soft
              Density is the weight of material that fills a given space. Water    brush, rinsed and repeated several times, then polished with a
              has a density of 1.0 g/cc and a pound of water takes up 27.5         soft brush or cloth. Only use soap on plaster, it is not suitable for
              cubic inches. Thus a pound of material with a density of 2 g/cc      sealing any other material. If the plaster is dry, it should be wet
              will only fill half the space or 13.75 cubic inches. When buying     for several seconds under running water prior to soaping.
              mold rubber or casting resin you must consider the price per
              volume, as the price per pound can be misleading. (See box on        Moist water clay, another special case, can be sealed and
              “Cost per cubic inch,” p. 4.)                                        released with Pol-Ease 2350 Release Agent or by spraying on a
              Elongation, reported in percent, is the length the material          10% solution of petroleum jelly in mineral spirits, made by
              stretches before breaking.                                           warming and melting the petroleum jelly and stirring in mineral
              Hardness is measured with a Durometer. It pushes a needle-           spirits. [Note: Use extreme caution since mineral spirits is highly
              like probe into the rubber as it is pressed against it. The          flammable.] Then apply the solution using a plant spray bottle,
              farther the needle penetrates into the sample the lower the          brush out and allow to dry. This prepares the water clay for
              reading. The Shore A scale is used for rubbers and the Shore D
              scale is used for plastics. Both scales go from 0 to 100. A          contact with most mold rubbers. If the water clay is completely
              rubber with a Shore A hardness of 0 is like warm chewing gum.        dry, it should be sealed and coated with release as for terra cotta.
              Shore A10 to 20 is about as soft as any mold rubbers can be.         Pol-Ease 2300 Release Agent must be applied to nearly every
              Shore A50 rubber is like a car tire. Above A80, rubbers feel         surface before pouring or applying liquid rubber (except
              more like a plastic and may measure on the low end of the
              Shore D scale. Shore D90 is about as hard as plastics get.           silicones) or resin. It should be sprayed evenly and then gently
                                                                                   brushed out with a dry brush to pick up any excess and to spread
              Pour time, working time, pot life or gel time give you an idea
              how much time you’ll have to work with a material from the time      the release over any spots missed by the spray. The brush should
              mixing begins until it gels. Most materials should be in place       be wiped with a paper towel periodically to prevent too heavy a
              well before the end of this time to allow good flow into detail      coating being left on the surface. Too much release can cause
              and for air bubbles to rise and break.                               pinhole defects in the surface of the liquid material poured
              Rheology describes how a liquid flows. A liquid is Newtonian if it   against it. The coating of release should be allowed to dry for
              flows and levels, even if very slowly. Pourable mold rubbers         about 15 minutes prior to pouring. Silicone-based release agents
              should be Newtonian. Brush-on mold rubbers may be                    like Pol-Ease 2300 may interfere with the cure of silicone mold
              thixotropic, that is they flow when brushed/troweled, but when
              undisturbed they stay where they are placed (see box on p. 8).       materials. When pouring silicones, use Pol-Ease 2350 on
                                                                                   surfaces that the liquid silicone will contact.
              Shrinkage is a reduction in size, which occurs with some
              plastics during cure or some rubbers after prolonged use.            If you have any question about the compatibility between the
              Casting materials draw oily materials out of the rubber causing      rubber and the prepared model surface, perform a test cure
              it to shrink. Products that develop heat during cure shrink as       on an identical surface to determine that complete curing and
              they cool. The degree of shrinkage increases with the
              temperature increase during cure. Some plastics get warmer in        good release are obtained. Some materials such as sulfur-
              the center than against the cool mold surface and tend to            containing modeling clays and wood knots, inhibit curing of
              cause the still liquid resin against the mold to sink. (See box on   some rubbers and plastics.
              “Exotherm,” p. 6.) Polytek products that stay cool during cure
              do not shrink while curing.                                          Securely fasten and seal side boards or shells to the base to
                                                                                   prevent leakage. Seal and apply release on all side boards and
              Tear strength is reported as the force needed to tear a split        shell interiors. Petroleum jelly is excellent for most non-critical
              one-inch long in a piece of material. Higher elongation rubbers
              generally have a higher perceived tear strength.                     surfaces like these, unless the material gets warm enough during
                                                                                   cure to melt the petroleum jelly. Pol-Ease 2300 Release Agent is
              Tensile strength is the force required to break a piece of
              material when pulled. It is reported in pounds required to break     more heat resistant, but is not self-sealing, so surfaces must first
              a one-inch square specimen of material.                              be well sealed.
              Viscosity, reported in centipoise (cP), describes if a liquid is     Porous models must be vented from beneath to prevent
              thick or thin. Water is low viscosity (1 cP), while pancake syrup    trapped air from forming bubbles in the rubber. A hole at least
              is higher (1000 cP), and honey is even higher (10,000 cP).           ¼-inch in diameter should be drilled through the base board into
              Temperature affects viscosity -- the lower the temperature,
              the higher the viscosity. For best flow into detail, Polytek         the porous model. The base of the model must be sealed around
              materials should be at least room temperature.                       the perimeter with Poly Plasticene or glue to prevent liquid
                                                                                   rubber from leaking under the model and through the vent hole.

      12
              Polytek          ®


              Development Corp.                                                                                       (610)559-8620 • (800)858-5990
                                                                                          Mold Making Methods                1




                                                                                                                                     Mold Making
MIXING THE MOLD RUBBER




                                                                                                                                      Methods
Have all materials at room temperature (75°F) before
mixing. It can take 24 hours for a 5-gal pail of material to
warm up to room temperature in the winter.
Have all materials and equipment clean and ready. Time is
critical to success. You do not want to go searching for tools
after you have mixed Parts A and B.
Stir individual components before use if recommended.
Some materials separate and will not cure properly if separated
material is used.
Weigh and measure accurately. Mix Ratios Vary! Check the             Before starting to mix rubber, have all materials at hand
mix ratios for the specific product you are using. For liquid        and at room temperature (75°F).
rubbers, most mix ratios are expressed by weight. Carefully
weigh Parts A and B in proper ratio. Weighing components                                            A Poly Paddle is an
on an accurate scale is a must. Only materials with a mix ratio                                     excellent tool for hand-
of 1:1 by volume can be measured by volume. Polytek does
                                                                                                    mixing liquid rubber without
not recommend trying to measure any other mix ratio by
                                                                                                    introducing excess air into
volume.
                                                                                                    the mix. Scrape the sides
Close containers tightly after use. Most materials are usable                                       and bottom of the mixing
at least six months to a year after shipment if unopened.                                           container thoroughly
Uncured polyurethanes, epoxies and some silicones react with
                                                                                                    several times while mixing.
atmospheric moisture and, therefore, should be used up as soon
as possible after opening. Before resealing, Poly Purge™ Dry
Gas Blanket (see p. 63) can be sprayed into open containers to
displace moist air and extend storage life.                              Carefully Adhere to Mix Ratios!
Time your actions with a clock. Start timing when you start
mixing. Try to have material poured and in place before half of         The chemistry of polyurethanes,
the working time has elapsed so there is plenty of time for
bubbles to rise away from the mold surface.                           silicones, and epoxies must add up.
Mix well, but avoid whipping air into the mix. Scrape the
                                                                     Unlike polyester resins, the recommended mix ratio
sides and bottom of the mixing container thoroughly several
times while mixing. A Poly Paddle is invaluable for good             of polyurethanes, silicones, and epoxies cannot be
mixing. Sometimes, to insure that no unmixed material is             varied without causing changes in the physical
clinging to the sides or bottom, the mix can be poured into a
clean container and mixed again for 1 to 2 minutes before            properties of the cured material. This is because to
pouring. For large mixes (i.e., >30 lb), a Jiffy Mixer (see p. 62)   cure 100 reactive groups of Part A, 100 reactive
on a variable speed drill can be helpful, but care must be taken
not to whip air into the mix or scrape the jiffy mixer blade
                                                                     groups of Part B are needed. If 100 reactive groups
against sides and bottom of the container.                           of A weigh two pounds and 100 of B weigh one
                                                                     pound, then the mix ratio must be two A to one B
                                                                     (2A:1B), by weight.

                                                                     Generally, if excess B is used the cured plastic will
      Avoid being rushed. Careful                                    be softer. If excess A is used the plastic will be
  planning allows for a deliberate                                   harder. But off-ratio mixes can cause other
                                                                     problems, such as no cure at all, dimensional
  pace without making mistakes.                                      instability, or short storage life of the cured rubber.


                                                                                                               Polytek           ®

                                                                                                                                     13
www.polytek.com                                                                                                 Development Corp.
              1    Mold Making Methods
Mold Making




              APPLYING THE MOLD RUBBER
 Methods




                                                                                                                                                                      Mold Making
                                                                                                                                                                       Methods
              Most often liquid mold rubber is poured over the model surface.
              With the development of Polygel products, however, applying
              liquid mold rubber to the model surface by brushing or spraying
              is becoming increasingly common. No matter how the liquid
              rubber is applied, one key is to avoid air entrapment. For poured
              molds, the liquid rubber should be poured in a steady stream
              into one corner of the mold box, allowing the liquid to flow over
              the model surface pushing air out ahead of it. In some cases,
              where there is exceptionally fine detail, some moldmakers feel
              that applying a small amount of mixed rubber to the surface and
                                                                                                                                 Mold rubbers are typically
              brushing or blowing it into the detail with low pressure air
                                                                                                                                 applied to a model by pouring,
              before pouring the bulk of the mix helps to ensure that the liquid
              pushes all the air out of the crevices. Caution must be taken that                                                 brushing, or spraying. Liquid
              brushing does not actually push the liquid through the film of                                                     mold rubbers with thixotropic
              release agent on the surface, causing sticking, or that release                                                    properties are ideal for brush and
                                                                                                                                 spray application. Think Polygel®.


                                                          How Much Liquid Rubber Do You Need?
               Poured Block Mold - Box Shape                                                Poured Block Mold - Cylinder Shape
               1. Calculate the volume of the box in cubic inches (in3).                    1. Calculate the volume of the cylinder.
                  V=lxwxh            where:     l = Length                                       V= π x r2 x h          where:     π = 3.14
                                                w = Width                                                                          r = Radius (½ diameter)
                                                h = Height                                                                         h = Height
                    e.g., 10 in x 5 in x 5 in = 250 in3                                          e.g., Using a 10-in tall section of 5-in diameter PVC pipe:
               2. Estimate the volume of the model.                                              3.14 x (2.5 in x 2.5 in) x 10 in = 196 in3
                  e.g., 8 in x 3 in x 3 in = 72 in3                                         2. Estimate the volume of the model.
               3. Subtract the estimated volume of the model from the                          e.g., 8 in x 3 in x 3 in = 72 in3
                  volume of the box.                                                        3. Subtract the estimated volume of the model from the
                  e.g., 250 in3 - 72 in3 = 178 in3                                             volume of the cylinder.
               4. Use specific volume data (refer to Technical Bulletin for                    e.g., 196 in3 - 72 in3 = 124 in3
                  specific product) to convert the volume to quantity of                    4. Use specific volume data to convert the volume to quantity
                  liquid rubber needed in pounds.                                              of liquid rubber needed in pounds.
                  e.g., Using specific volume of Poly 74-30 Liquid Rubber                        e.g., Using the specific volume of Poly 74-30 Liquid Rubber of
                  (27.5 in3/lb):                                                                 27.5 in3/lb:
                  178 in3 ÷ 27.5 in3/lb = 6.5 lb Rubber                                          124 in3 ÷ 27.5 in3/lb = 4.5   lb Rubber
                Note: For this hypothetical model, far less liquid rubber is needed for the cylindrical mold. Choose your containment area carefully.

               Brushed/Sprayed Blanket Mold                                                Poured Blanket Mold
               1. Estimate the surface area of the model. Depending on the                  Poured blanket molds are usually made by covering a model
                  complexity of the model, this can be difficult and it may be              with clay, making a shell, removing the clay, and filling the
                  necessary to consider a model in sections and add up all                  area once filled by clay with liquid rubber. Therefore, the
                  surface areas. If the model is basically rectangular, use the             volume of clay equals the volume of liquid rubber needed.
                  surface area equation for a rectangle; if cylindrical use the                 e.g., If a block of clay with a volume of 64 in3 was removed
                  surface area equation for a cylinder (A = 2πr2 + 2πrh).                       from the model and Poly 74-30 Liquid Rubber (spec. vol.
               2. Multiply the surface area by the thickness of the blanket                     27.5 in3/lb) is to be used:
                  mold (usually 0.25 in to 0.38 in) to determine the volume
                  of liquid rubber needed.                                                      64 in3 ÷ 27.5 in3/lb = 2.3 lb Rubber
               3. Use specific volume data to convert the volume to quantity
                  of liquid rubber needed in pounds


      14
              Polytek             ®


              Development Corp.                                                                                                   (610)559-8620 • (800)858-5990
                                                                                               Mold Making Methods                      1




                                                                                                                                               Mold Making
does not float to the top of the brushed liquid, preventing                                                         This blanket mold of a




                                                                                                                                                Methods
adhesion between the poured material and the brushed material.                                                      baluster is stored
                                                                                                                    properly in its mold
For more information on applying liquid mold rubber by brush
or spray, refer to Polygel product information (see pp. 36-37).                                                     shell. The thin mold of
                                                                                                                    PlatSil® 73-45 is
If a super smooth mold back is desired, a light spray of Pol-Ease                                                   supported by a firm
2300 Release Agent on the top surface of the liquid just before it                                                  shell made from Poly
gels breaks most of the surface bubbles.                                                                            75-80 Liquid Rubber.

CURING THE MOLD
Cure at the same warm temperature that all your materials were         STORING THE MOLD
when mixed. Temperatures below 65°F lengthen the time                  Proper storage of molds cannot be overemphasized and is the
required for proper curing and may spoil the cure of some              key to extended “library life” -- the time that a mold remains
materials. Placing the poured mold or casting in a warmer area         useful after storage. Some rubber molds, if stored properly, can
than the materials were when they were poured, can cause               have a library life of ten years or more.
problems because changing temperatures while the material is
                                                                       Store molds in their original, undistorted shape. Molds should
setting can cause bubbles or distortion.
                                                                       be left in the mother mold, mold box or on a surface that causes
Check product technical bulletin for proper cure time. Demold          the least distortion possible. If rubber is left in a distorted shape
carefully as the material is still more tender than it will be a few   for any length of time it can take a permanent set and may never
days later. Bending or forcing a material while it is still only       recover to its original shape.
90% cured can cause distortion that may not recover.
                                                                       If a blanket mold is stored in a mother mold/shell made of
                                                                       porous material, such as bare plaster, the shell surface that
USING THE MOLD                                                         contacts the mold must be sealed (e.g., with shellac). Sealing the
More rubber molds fail due to poor handling than by wearing            shell prevents it from absorbing oils from the mold rubber
out. Proper design, careful handling and attention to detail           which, in turn, can cause mold distortion.
prolong mold life.                                                     Do not allow molds made of one type of rubber to remain in
When casting plaster, wet the rubber mold with Pol-Ease Mold           contact with molds of other rubbers as migration of oils or
Rinse or a 1% detergent (e.g., Ivory Liquid) solution in water         plasticizers from one to another can cause swelling, shrinkage,
before pouring the plaster. Wet the mold by dipping or spraying.       or distortion.
Pour the plaster on the wet surface. [Note: Detergent is               Poly-Fast 72-40 molds may soften over a period of 2-4 years.
chemically different from soap. Do not use soap -- Ivory Liquid        TinSil silicone molds may embrittle (i.e., lose tear strength and
is a detergent.]                                                       elongation) over a similar period. These mold materials should
When casting plastics in polyurethane or silicone molds, first         not be selected if long library life is required.
coat the mold with a release such as Pol-Ease 2300 Release             Molds should be stored in a cool, dry area and out of the
Agent. Release agent is not always needed in silicone molds.           sunlight, which can degrade the surface.
Spray a light even coat of Pol-Ease 2300 on the mold surface
and then carefully brush the surface with a clean, dry brush to
pick up any excess and cover any missed spots.                          Colors for Polytek Products
PVA is a barrier to migration of plasticizers and chemical attack       Most Polytek Liquid Rubbers & Plastics can be colored with
by harsh casting resins. Poly-Fast 72-40 rubbers contain                the use of proper dyes or pigments. PolyColors, reactive liquid
plasticizers that can soften resin surfaces producing soft or           dyes available from Polytek in red, green, yellow, blue, brown
sticky castings. If resins are to be cast in 72-40 molds, first coat    and black, can be used in most Polytek polyurethane
the mold surface with PVA and allow to dry, then lightly spray          products. In addition, PolyColors can be added to certain
with an even coat of Pol-Ease 2300. This surface treatment              silicones in small concentrations. Polyurethane rubbers and
often acts as a barrier to the plasticizers. PVA can be washed off      plastic can be lightly tinted or made vibrant and dark in color
castings with soapy water. PVA also prolongs the life of                by using PolyColors up to 3% by weight of the total liquid mix.
polyurethane molds when casting polyester resins.                       PolyColor Brown is excellent for creating a base color when
For long mold life, avoid exposing rubber molds to strong               making cold cast bronze parts. PolyColor Black can be used
solvents, oils or cleaners. Sprayed release agents reduce solvent       to make even the whitest plastics true black. Since PolyColors
exposure as compared to brush application.                              are dyes, not pigments, they mix in easily and do not settle in
                                                                        the liquid rubber or plastic when properly mixed. Use
                                                                        PolyColors individually or in combination to make any color
                                                                        imaginable. For product information, see p. 61.


                                                                                                                        Polytek            ®

                                                                                                                                               15
www.polytek.com                                                                                                         Development Corp.
              1    Mold Making Methods
Mold Making




                                                                                   painting by detergent washing. If a prime coat is desired on the
               CASTING & FINISHING
 Methods




                                                                                   cast part, a barrier coat can be sprayed on the mold before
               For simple solid casts, the flexible mold and shell (if required)   casting. Paint enhances and protects plastic castings and is
               are positioned so the opening is level and release agent, barrier   necessary for best exterior durability.
               coat or rinse is applied, if necessary. The casting material is
               poured right to the top edge, vibrated if necessary and allowed
               to cure. Most casts should be removed as soon as they are
                                                                                   CLEANUP
               adequately set, since longer residence times can damage some        Tools should be wiped clean with paper towels before the rubber
               mold materials.                                                     cures. Casting plastics are extremely difficult to remove from
                                                                                   tools once cured. Be sure to clean tools as soon as possible.
               Use of vacuum or pressure (see box below), brushing, spraying
                                                                                   Denatured ethanol is a good cleaning solvent, but it must be
               or heated molds are all helpful techniques to eliminate bubbles
                                                                                   handled with extreme caution owing to its flammability and
               and achieve perfect casts of highly detailed parts, but simple
                                                                                   health hazards. Work surfaces can be waxed or coated with Pol-
               pours are often adequate.
                                                                                   Ease 2300 Release Agent so cured rubber and plastic can be
               Trim and touch up, is easiest while the casting is warm and is      removed.
               best done just after demolding. Remove release agent prior to



                                                                                   capacity can be a frustration. You may find your material
               VACUUM & PRESSURE CASTING                                           gelling before it is free of bubbles. Buy a large enough vacuum
               Perfect Castings Made Easily!                                       pump that will get down to maximum vacuum quickly so you
                                                                                   can degas and pour before your mixed material thickens or gels.
               Although many excellent bubble-free molds and castings are          A Welch Model 1397 can often be purchased from equipment
               made with Polytek rubbers and resins every day, trapped air         dealers for ~$3,000 new or ~$1,500 used. It pulls 17.7 CFM and
               bubbles create the most common defects. Proper use of               works well with a 40-quart pot.
               vacuum or pressure can eliminate bubbles from some kinds of
               castings and molds and is often cheaper and easier than you         Pressure
               might think. The following applies only to non-porous molds
                                                                                   Using pressure to eliminate bubbles can be even more useful.
               and models -- porous materials such as wood and plaster do
                                                                                   The process is like reversing the opening of a bottle of soda.
               not lend themselves to use of vacuum and pressure.
                                                                                   When pressure is applied to liquid rubber or resin, small
               Vacuum                                                              bubbles are forced into solution and disappear. To accomplish
                                                                                   pressure casting, pour the resin or rubber and place the whole
               Using vacuum to pull air bubbles out of mixed liquid rubber or      mold in a pressure pot before the material begins to set. Fasten
               resin can often be very helpful. Place the container of mixed       the lid and pressurize to ~60 psi with compressed air or
               liquid rubber or resin in a vacuum chamber and draw about 28        nitrogen. Allow the cure to take place under pressure. You will
               inches mercury so that the largest air bubbles rise to the          be amazed with the results.
               surface. You must perform degassing while the mix is still
                                                                                   Inexpensive pressure pots typically used by spray painters are
               liquid. Do not attempt to “vacuum degas” Polytek rubbers or
                                                                                   available from paint supply stores and industrial supply houses
               resins with short work times -- this can result in creating more
                                                                                   such as Grainger.
               bubbles. Some liquids rise 2 to 3 times their original volume
               during degassing, so use a container with adequate head             Caution: Vacuum and
               space. Once degassed, the liquid should be poured carefully so      pressure systems can be
               that air is not reintroduced into the mix.                          dangerous. If you have any
                                                                                   questions       about     the
               Simple vacuum chambers can be constructed from pressure
                                                                                   construction or operation of
               pots as well as from sturdy commercial cooking pots by
                                                                                   your vacuum or pressure
               making a transparent cover of 1-inch Plexiglass with a
                                                                                   system, consult with a
               cemented hose fitting and 1/4-inch thick gasket of Poly 74-55.
                                                                                   qualified engineer. Never
               A T with 1/2-inch ball valves is used to control and release the
                                                                                   use glass parts unless they
               vacuum, one valve on the vacuum line and one as a vent.                                                  Welch Model 1397 vacuum
                                                                                   are certified for the purpose.
               Vacuum pumps can be purchased from laboratory equipment                                              pump with a 40 quart pot and lid
               dealers. A vacuum pump that is too small with insufficient                                              made with Poly-Optic® 1410.



      16
              Polytek          ®


              Development Corp.                                                                                       (610)559-8620 • (800)858-5990
                                                                                                  Mold Making Methods                        1




                                                                                                                                                       Mold Making
POURED MOLDS




                                                                                                                                                        Methods
One-Piece Block Mold                                                                         Poured mold rubber
To make a poured block mold the model must be securely
fastened (e.g., screwed or glued) to a base board. Kitchen
countertop sink cut outs make excellent base boards. If the
                                                                                                Sealed and released model
model is porous, a vent hole should be drilled through the
baseboard to the model to allow air to escape. Sides of the mold
containment area must be positioned and sealed to the base
board (e.g., with plasticene or hot melt glue) so that liquid            Screw model to base                    Vent hole
rubber cannot leak out. If the mold will be used without being
placed in a box for support, then be sure to position the sides far      base and sides of the box are properly sealed and released, slowly
enough from the model such that the rubber mold will be thick            pour liquid rubber directing the flow to the bottom of the box and
enough that it will not deform when it is full of casting material (at   being careful not to trap air bubbles as the liquid rises. The rubber
least 0.5-inch thick). Sometimes a strap is placed around the finished   should be at least 0.5 inches above the highest point on the model
mold box to ensure that it all holds together. Once the model and the    (mark the mold box before you start pouring liquid rubber).

Cut Block Mold                                                           should be decided before the mold rubber is poured, marked on
                                                                         the mold box and then transferred to the cured rubber mold. To
A block mold can be cut when cured to make a split or multi-             cut the mold, use a mold key knife (see p. 62), which has a sharp
piece mold. With some models, the mold must be cut to allow              blade with a groove that creates a tongue and groove effect in
for removal of the model. Sometimes the cut is simply a single           the cut rubber. This makes reassembling the mold with the
slit up one side of the mold, while in other cases a single-piece        seams properly aligned possible. Vents and pour holes can be cut
block mold can be cut into multiple pieces to create a complex           or drilled into the cured rubber, or can be formed with rods or
multi-piece mold. In either case, after the model is removed, the        plasticene prior to pouring the rubber. When casting, cut block
mold is reassembled by carefully lining up the seams and                 molds are reassembled and typically placed back into the
usually returned to its box to hold it together before casting           containment area with the pour hole at the top for filling with
material is poured into the mold.                                        casting material.
For a successful cut block mold, the key is in the cutting. First,       Sometimes, block molds poured as one piece are the fastest to
select a rubber with an appropriate hardness for cutting (i.e.,          make even for oddly shaped models; but they require more
Poly 74-30, soft Shore A30). Next, carefully evaluate where the          liquid rubber than blanket molds. Making quality, multi-piece
cut(s) will be made (i.e., possibly up the back of the head, not on      block molds requires considerable practice and expertise.
the face) and how many cuts are required. The cutting locations

Split Block Mold                                                         Multi-Piece Block Mold

                                            This head mold is             Chunk cut out to
                                            cut from a cylinder of        remove ears
                                    Mold
                                            cured rubber. The
        Rubber                      Strap
                                            containment area is
                                            a piece of PVC pipe
                                            sealed to a base-
                  Model                     board with plasticene                                     Vent
                                                                         Chunk cut out to
                                            or hot-melt glue.
                                                                         release front end
                                            After the rubber
                                            cures, the pipe is
                                            removed from the
                                                                                     Plug cut out from between legs         Split to remove tail
                                            base and cut with a
saw to remove the mold. The rubber is cut with a mold key knife          This horse mold is cut from a single block of mold rubber. After
in a predetermined location to make a slit that allows for               pouring, curing and cutting the mold, it is reassembled and
removal of the model. To avoid damaging the model, the first cut         placed back into the mold box upside down for casting. Casting
should not go completely though to the model, but rather the             material is poured through the feet. As an alternative, the mold
final cut through is made with a razor. When casting, the seam           of the horse model could be made as a blanket mold poured into
is carefully realigned and the mold is strapped together. The            a pre-constructed shell -- this would mean easier cutting of the
mold is inverted and casting material is poured into the opening.        thinner blanket mold and using less mold rubber.


                                                                                                                            Polytek                ®

                                                                                                                                                       17
www.polytek.com                                                                                                             Development Corp.
              1       Mold Making Methods
Mold Making




              POURED MOLDS (CONT’D)                                                      1                                      2
 Methods




                                                                                                                                               positioning key
                                                                                                 mold rubber

              Block Mold Poured in Two Pieces
              A block mold can be made by pouring two pieces of the mold
              separately. First, one portion of the model is embedded in clay                                       clay                         mold rubber
              up to the desired parting line. Then liquid rubber is poured over
              the properly prepared, exposed portion of the model (1). After             First pour                             Ready for second pour
              the rubber cures, the clay is removed and release agent is applied
              to the other side of the model and the cured rubber surrounding             3   vent     pour hole   vent
                                                                                                                                    Mold ready for
              it. Rubber is then poured over the second half of the model (2).
                                                                                                                                    casting
              Once cured, a pour hole is cut through the rubber mold and, if
              necessary, vent holes are drilled through high spots in the mold
              to eliminate the possibility of trapped air bubbles. The mold is
              repositioned in its box and is ready for casting (3).


                                                                                         The shell is made overtop of the clay usually by brushing on
              BLANKET MOLDS                                                              liquid plastic. Plastic mold shells are lightweight and durable
              Poured Blanket Mold                                                        and are typically made of Polygel Plastic or another liquid
                                                                                         plastic (e.g., 15-6 or 1512X) thickened with an additive (e.g.,
              Generally, to make a poured blanket mold, the model is covered             Poly Fiber, see p. 61). The first section of the mold shell is built
              with clay and the mold shell is built over the clay-covered                up against the clay flange. When the first section of shell is hard,
              model, then the clay is removed and the liquid mold rubber is              the clay flange is removed, wax and then release is applied to
              poured in the void left by the clay.                                       the edge of the first shell section and the second section is built
              First the model must be properly prepared (e.g., sealed and                against the first section for a perfect keyed fit of the shell
              released) and mounted. Then the model is covered with plastic              sections.
              wrap to protect it before the clay is applied. The clay blanket is         To make the rubber mold, the clay and plastic wrap is removed
              formed around the model and must fill-in any undercuts so that             from the model and then rubber is poured into the shell filling
              the mold shell cannot lock to the rubber mold. Since the shell is          the void left behind. The rubber mold can be poured in one piece
              often made in two (or more) pieces, the clay is formed with                and cut with a mold key knife after curing. Or, for a two-piece
              protruding flanges, which act as parting lines for the shell. In           mold, half of the clay is removed and rubber is poured in the
              fact, since the rubber replicates the clay blanket exactly, parting        void along half of the model. After the rubber cures, clay on the
              or cut lines should be delineated in the clay for transfer to the          other half is removed, release is applied to the model and cured
              rubber. Sometimes “snaps” are placed along the clay blanket so             rubber, and liquid rubber is poured into the void along the
              that the rubber mold will “snap” into position in the mold shell.          second half of the model (see story with photos on pp. 22-23).

              Cover the model with clay, then build the mold shell.                      Then pour liquid rubber into the shell.
                Shell                Clay flange    Shell                   Clay plug
                                                                                                               Liquid rubber                 Shell parting line
              (1st half)             with groove                             to make
                                                                            pour hole
               Clay                                                           in shell                             Mold strap
                                          Snaps
               Vent


                             Model                              Vent



              The prepared model is protected with a covering of plastic wrap
              and then a clay blanket (~0.5-inch thick) is built over the model.
              The shell is made over the clay by brushing on liquid plastic. The         After the clay is removed, liquid rubber is poured into the void.
              shell plastic is first applied to one half and cured. Then the clay        When making a one-piece or cut mold, all of the clay is removed
              flanges are removed and release agent is applied to the exposed            and the entire space is filled with rubber. If necessary, the cured
              plastic and the second half of the shell is built up to the first half.    rubber is cut to remove the model.



      18
              Polytek           ®


              Development Corp.                                                                                                 (610)559-8620 • (800)858-5990
                                                                                                   Mold Making Methods                       1
Brush-On Blanket Mold                                                     in the rubber mold that can lock the shell onto the rubber when




                                                                                                                                                    Mold Making
                                                                                                                                                     Methods
                                                                          there is a casting/model inside the mold (see box).
A brush-on blanket mold is made first, then the shell is made
over top of the cured mold for support. Some one-piece blanket            The parting line for the rigid shell is defined with a clay (i.e., Poly
molds are simply peeled off a low-relief or pyramid-shaped                Plasticene) flange applied over the mold. A groove or depressions
model (“sock” mold). But, often it is necessary to create a seam          should be made in the clay where it contacts the shell material to
or cut a split in the mold to allow for removal of the model and          create good locking and positioning of the shell halves. The mold
castings. To create a parting line in the blanket mold, thin shims        shell is built one section at a time against the release coated rubber
(e.g, aluminum flashing or stiff plastic sheet) are positioned on         mold and clay flange. When one section of the shell is complete,
and securely fastened to the model. In lieu of shims, rubber can          the clay is removed, Vaseline or butcher’s wax is applied to the
be brushed thick enough in areas so that the cured rubber can be          exposed shell followed by a release agent, and the next shell
cut to permit demolding. This technique is helpful for masters            section is built against the first. The two halves of the shell
with “through holes” that can lock the rubber mold to the master          compress the rubber flanges along the mold opening together
(see pp. 20-21).                                                          making a good seal so that liquid casting material cannot leak out.
If needed to prevent trapping air bubbles during casting, vents            First, the model is prepared for making the blanket
are formed in the mold by neatly fastening thin straws or rods to
                                                                           mold. Then thixotropic mold rubber is brushed on.
the model. Remember, neater fastening means less cleanup of
the casting. After the model, shims and vents are coated with                                                     The model is prepared (i.e.,
release, liquid rubber is brushed on.                                                                             sealed and released) and
                                                                                                                  securely mounted to a base.
Sometimes with large models, it’s a good idea to create “snaps”
                                                                                                                  A vent is drilled through the
or keys on the rubber mold to hold the mold in place in its shell.
                                                                                                                  base to release air trapped
The shell may need to be more than one piece in order to allow                                                    in the model. Thin shims are
removal from the rubber blanket mold. There can be no undercuts                                                   placed along the model and
                                                                                                       Shims
                                                                                                                  in spaces formed under the
 Dealing with Undercuts                                                                                           legs and arms. The shims
                                                                                                                  form a parting line in the
 When making a brush-on blanket mold, Brushed-on rubber
                                                                                                                  brush-on rubber blanket
 all undercuts in the model must be
                                                                                                                  mold. Once the shims are
 eliminated before the mold shell is
                                                                                                           Vent   secure, the rubber is
 made. Typically, undercuts are filled
                                                             Filled                                               brushed on in several coats
 with mold rubber or another filler
                                                             space                                                to ¼- to ½-inch thick.
 material -- even air. Sometimes the filler       Model
 must be compressible so that the mold
                                                                           After the rubber cures, the rubber-coated model is
 can be removed from the model. A hollow
                                                                           prepared for construction of the mold shell.
 bladder can be formed by bridging the undercut area with a piece
 of plastic wrap pressed into the previous layer of rubber. Then                                 Rubber-CoveredA clay flange is formed
 another coat of rubber can be brushed overtop of the plastic                                    Model         around the model to define
                                                                          Clay Flange
 wrap. If more support is needed. the undercut can be filled with a                                            the parting line of the rigid
 material such as soft foam then covered with liquid rubber.                                                   mold shell. Depressions are
 In lieu of filling undercuts, a flexible mold shell can be built                                              made in the clay that will
 instead of the standard rigid mold shell. A flexible mold shell                                               form “snaps” in the mold
 (e.g., made of Poly 74-30 rubber) can be removed from                                                         shell to help properly lock
 simple undercuts in the blanket mold and can sometimes                   Snaps                                the mold shell halves
                                            alleviate the need for a                                           together. In addition, rubber
                       Flexible 74-30                                                                          snaps can be placed on the
   Rigid shell                              multi-piece shell. A soft,
                       mother mold
                                            polyurethane rubber (e.g.,                                         rubber mold so that the mold
                                   Brush-on Poly 74-30) can be poured                                          snaps to the mold shell. The
                                     mold
                                            over a release coated                                              first half of the rigid mold
                                            blanket mold enclosed in a                                         shell is built up to the clay
                                            simple box or rigid mold.                                          flange. Then, the clay is
                                            Although this option may be                                        removed and the second
                                            more expensive since it       half of the shell is constructed. When complete, the two halves
                                            uses more rubber, it can      of the shell compress the rubber along the mold opening to
                                            save on labor.                make for a good seal along the mold opening.



                                                                                                                            Polytek             ®

                                                                                                                                                    19
www.polytek.com                                                                                                              Development Corp.
              1    Mold Making Methods
              Procedures - Brush-On Mold
Mold Making
 Methods




              Making a Brush-On Blanket Mold with a Plastic Shell
              The following example details the procedures involved in               (Photo 6). When this layer
              making a brushed mold. The rubber that has been chosen is Poly         is complete, the freshly
              74-20, a soft, stretchy, 1A:2B by weight mix ratio, polyurethane       gelled strip of Poly 74-20
              liquid mold rubber. Of course, there are many variations to this       rubber is removed from
              technique and several choices of rubbers. We could have chosen         the 71-20 silicone mold
              to make a one-piece brushed mold with shims similar to what is         and positioned against the
              shown on page 19. We just as easily could have made a two-             mold where the seam line
              piece mold where we need no cuts to remove two separate                will be cut once the mold
              halves of the rubber mold.                                             cures (Photo 7).
              This example specifically demonstrates how to create a one-            A final coat of lightly
              piece brushed mold without shims, which will require cutting a         thickened rubber is applied
              seam in the rubber to remove the original and subsequent               after the prior coat gels to
              castings. The master, shown in Photo 1, is made of a non-porous,       seal in the seam line strip
              polyurethane plastic, EasyFlo 60. As with all sealed, non-porous       and to make a smooth
              masters, they must be sprayed with a silicone release such as          outer coating, which makes the rubber mold more attractive and
              Pol-Ease® 2300 Release Agent (when using polyurethane liquid           fit better into its rigid support shell (Photo 8). Once the rubber
              rubber) and brushed with a clean, dry brush to insure uniform          mold cures (overnight, or later that day if 74 Part X accelerator
              distribution of the release. Care is taken not to spray too much       is used), it is trimmed at the base and a clay wall is built up to a
              release since brush marks can be left behind and picked up in the      line that will define the parting line of the two shell sections
              finished mold. Also, excess release can be accidentally pushed         (Photo 9). Since the shell will be rigid, there can be no undercuts
              around when brushing liquid rubber resulting in delamination           that will lock it onto the rubber mold. More complicated models
              between coats or unwanted surface texture.                             may require more shell sections to insure that they can be easily
              In Photo 2, Cab-O-Sil® powder is added to the mixed Poly 74-20         removed. Notice the keys/grooves in the clay wall that will
              rubber to make it thixotropic so it clings to vertical surfaces. The   insure proper registration of the shell halves. Butcher's wax is
              Cab-O-Sil is added in small amounts while the liquid is folded         brushed over the rubber mold, allowed to dry for 10 minutes,
              over carefully to wet the powder (so it doesn't come out of the        then sprayed with a coat of Pol-Ease 2300 Release Agent.
              cup), then it is whipped into the rubber to a creamy, uniform          To make the shell, Poly 1512X Polyurethane Liquid Plastic is
              consistency. Only a slight amount of thickening is desired in the      mixed together (1A:1B), then Poly Fiber thickener is added to
              first coat of rubber so all surface detail is captured without         make it thixotropic (Photo 10). Poly Fiber is added until the
              trapping bubbles at the mold surface. Photo 3 shows a thin, first      resulting mix clings to the side of the mixing container. The
              coat of lightly thickened Poly 74-20/Cab-O-Sil being applied           thickened 1512X is applied ~¼-inch thick and allowed to cure
              with a China bristle brush. After the first layer of rubber gels       ~60 min (Photos 11). The clay wall is removed, butcher's wax
              enough to be undisturbed by the next coat (~45 min - faster with       and Pol-Ease 2300 applied to the other side of the mold and
              Part 74 Part X), a second coat of slightly thicker (a little more      against the first shell section and the above procedure with
              Cab-O-Sil used) 74-20 is brushed over the first coat (Photo 4)         1512X is repeated. The completed shell is drilled, bolted and
              and allowed to gel. Before Cab-O-Sil is put into the rubber to         edges sanded for easier handling (Photo 12).
              create the mix used for the third layer, a little unthickened Poly     When the shell is removed, a mold key knife is used to cut a
              74-20 is poured into a PlatSil® 71-20 silicone mold to make long       notch in the rubber the length of the seam from head to toe. A
              1-inch by 1-inch strips (Photo 5) for creating a thick rubber          sharp scalpel is then used to cut the rest of the way to the master.
              flange that will be placed into the freshly gelled third coat of       As the rubber is peeled open, cuts are made between the legs and
              rubber to define the location of the seam line. Notice that this       arms as needed to remove the original. Cutting in these areas is
              model has several "through holes" (between the arms and the            done using a series of short, jagged, zig-zag cuts in order to
              legs) that need to be filled completely with liquid rubber to          create a series of tiny keys that keep the seam registration exact
              provide a thick enough section of rubber which will be cut when        (see photo above). The finished mold and shell are now ready
              cured to remove the original. This third layer is done with an         for production!
              even more thixotropic, non-sag mix of 74-20 and Cab-O-Sil



      20
              Polytek           ®


              Development Corp.                                                                                         (610)559-8620 • (800)858-5990
                                          Mold Making Methods        1
                                        Procedures - Brush-On Mold




                                                                            Mold Making
                                                                             Methods
Photo 1           Photo 2    Photo 3              Photo 4




Photo 5           Photo 6    Photo 7              Photo 8




Photo 9           Photo 10   Photo 11             Photo 12




                                                        Polytek         ®

                                                                            21
www.polytek.com                                         Development Corp.
              1    Mold Making Methods
              Procedures - Poured Blanket Mold
Mold Making
 Methods




              Making a Two-Piece Poured Blanket Mold in a Plastic Shell
              This page details the step-by-step production of a flexible rubber   To build the shell for the
              mold and plastic mother mold of the 19-inch-tall, 19th-century       first half of the mold, Poly
              marble statue entitled Ice Skater by Gori Nello.                     Fiber was stirred into mixed
                                                                                   Poly 15-6 Liquid Plastic
              Deciding on the Type of Mold
                                                                                   until it was the consistency
              Openings under the arms and legs presented typical difficulties
                                                                                   of cake frosting. Then, the
              that influenced the selection of the type of mold to be
                                                                                   thickened resin was laid on
              constructed. The moldmaker decided on a blanket mold, poured
                                                                                   the first half of the clay in a
              in two halves into a constructed shell, because pouring yields
                                                                                   manner similar to icing a
              better detail with less trapped surface bubbles. A poured mold
                                                                                   cake. [Note: When making
              also eliminates undercuts more easily than a brush-on mold. A
                                                                                   larger shells, multiple mixes
              double pour, with carefully selected parting lines, eliminates the
                                                                                   of resin and Poly Fiber can
              need for shims (see p. 18), which would leave flashing to be
                                                                                   be patched against each
              chased, and cutting, which would be required with a single-pour                                       The original marble and plaster
                                                                                   other to cover the entire
              mold and could scratch the valuable sculpture.
                                                                                   surface.] After the first half and plastic reproductions made in
              Selecting the Materials                                              of the shell cured (~4 hours),      the Poly 74-30 blanket mold.
              Poly 74-30, a two-part, 1:1 mix polyurethane liquid rubber, was      the aluminum shims were
              used for the mold since it is low cost, easy to mix and pour,        removed and paste wax (i.e., Butcher’s Wax) and then release
              flexible (Shore A30), and has good longevity. Poly 74-30 molds       agent were applied to the first half of the shell (Photo 4). The
              work well for casting plaster, cement, wax or resins.                second half of the shell was built against the first half in the
              The mold shell was made with Poly 15-6, a 1:1 mix liquid             same manner (Photo 5).
              plastic with a 5- to 7-minute working time. The plastic shell is     Pouring the Rubber
              lightweight and durable. [Note: Alternative materials for making     One-half of the plastic shell was removed along with the clay
              mold shells are plaster reinforced with hemp or burlap, Polygel®     blanket beneath that half of the shell. Keys (tongue-and-groove
              Plastic-75, or Poly 1512X with Poly Fiber. The larger the shell,     impressions) on the second half of the clay were made in order
              the more important it is to use lightweight shell materials.]        for the two halves of the rubber mold to “key” or lock together
              Preparing the Statue                                                 (Photo 6). Vent holes were drilled in the shell with a ¼-inch drill
              First, the marble statue was fastened to the base with Polypoxy®     at each high point where air would be trapped (Photo 7). The
              Quick Stick Adhesive. The base was formica-coated particle           shell was thoroughly coated with release agent, replaced and
              board from a countertop sink cut-out. To protect the marble from     positioned for pouring the rubber. Poly 74-30 was mixed and
              the oils of the release agent, a thin layer of PVA (polyvinyl        poured into the space within the shell where the first half of the
              alcohol) solution was brushed directly on the marble. (PVA           clay had been. When pouring the rubber, the model was at the
              solution washes off with warm water.) After the PVA dried, a         bottom of the cavity so the air bubbles would rise away from the
              liberal coat of release agent was sprayed over the model and         model surface. As liquid rubber appeared at the vent holes, they
              brushed out with a dry brush to pick up any excess and to work       were plugged with plasticene clay (Photo 8).
              release into any areas missed by the spray (Photo 1).                After the rubber cured overnight, the shell and clay on the
                                                                                   second half was removed and release agent applied to the model
              Building the Mother Mold
                                                                                   and the face of the cured rubber parting line (Photo 9). The shell
              Next, the statue was wrapped in plastic wrap to keep it clean
                                                                                   was reassembled and rubber was poured into the shell to cover
              (Photo 2). Then, a ¼-inch blanket of Poly Plasticene (oil-based
                                                                                   the model’s second half.
              clay) was hand pressed onto the plastic wrap. To make the clay
              uniform thickness, warm Poly Plasticene (~130°F) was placed          After the rubber cured, the shell halves were separated by
              between 2 equal height wood strips and rolled flat using a PVC       tapping wood wedges into the seam, gradually forcing open the
              pipe. The height of the wood strips (¼- to ½-inch) determines        shell to reveal the complete mold (Photos 10 and 11).
              the thickness of the clay blanket. All undercuts were filled with    The Casting
              Poly Plasticene so the shell could be easily removed.                Plaster was poured into the mold to clean and check the mold.
              Shims of thin aluminum flashing were placed in the clay to           Finally, release agent was applied, brushed out and the mold was
              create parting lines for the shell (Photo 3). These are the only     properly positioned in its shell. Poly 15-3X, a mineral-filled,
              shims needed with the double pour process to make this mold. A       fast-setting polyurethane casting resin, was poured into the mold
              channel was built around the edge of the clay to cause the rubber    (Photo 12). The final casting was demolded in less than an hour.
              mold to lock into the shell.                                         The excellent reproductions are shown with the original above.



      22
              Polytek          ®


              Development Corp.                                                                                      (610)559-8620 • (800)858-5990
                                        Mold Making Methods         1
                                Procedures - Poured Blanket Mold




                                                                           Mold Making
                                                                            Methods
Photo 1           Photo 2    Photo 3             Photo 4




Photo 5           Photo 6    Photo 7             Photo 8




Photo 9           Photo 10   Photo 11            Photo 12




                                                       Polytek         ®

                                                                           23
www.polytek.com                                        Development Corp.
              1     Mold Making Methods
              Applications - Sculpture & Foundries
Mold Making
 Methods




                                                                                                          B
                                                                                                    ill Hopen, Hopen Studio in Sutton,
                                                                                                    WV, uses Poly 74-30 thickened with
                                                                                                    Cab-O-Sil® to make a brush-on
                                                                                             mold of his clay “St. Joseph the Worker.”
                                                                                             Three to four layers of mixed Poly 74-30
                                                                                             are applied at 60- to 90-minute intervals.
                                                                                             The first layer contains little or no Cab-O-
                                                                                             Sil so that air bubbles are minimized and
                                                                                             fine details are reproduced. More Cab-O-
                                                                                             Sil is added to subsequent layers for faster
                                                                                             build up of the ¼- to ½-inch mold.
                                                                                             Twenty-four hours after the final layer,
                                                                                             Hopen builds a rigid mold shell. The great
                                                                                             flexibility of rubber molds allows for easy
                                                                                             demolding of delicate wax castings. The
                                                                                             long mold life of Poly 74-30 has enabled
                                                                                             Hopen Studio to continue producing
                                                                                             castings 10 years after some molds were
                                                                                             made. These molds are made much more
                                                                                             quickly than latex molds and at a fraction
                                                                                             of the cost of silicone molds. Bill says
                  Poly 74-30 Liquid Rubber thickened with Cab-O-Sil ® -- Sculptor Bill Hopen “I’ve tried them all; Polytek Mold Rubber
                                                                                             is the best.” For sculpture by Hopen call
                                                                                             (304)765-5611.


              Architectural Restoration


                T     HR Cast Stone and GFRC of Brooklyn, NY, has restored
                      many of the most architecturally significant buildings in
                      New York City. Whether the medium is brownstone,
                limestone, terra-cotta, plaster, or stone, the artists, moldmakers,
                and casters at THR have reproduced and restored it to match its
                original beauty. Newly cast parts made from cast stone, glass-
                fiber-reinforced concrete (GFRC), or glass-fiber-reinforced
                gypsum (GRG) appear original in every way. THR has used
                Polytek products to recreate ornamental architectural elements
                in theaters such as Lyric and Ed Sullivan, museums such as the
                Metropolitan, and hotels like the Plaza and Ansonia, as well as
                churches, schools, and private residences. THR prefers Polygel®
                rubbers (see p. 36) for brush-on or sprayed molds that are
                created on-site from an element before it is removed from the
                building. For work back at the shop, THR often opts for Poly          THR Gives New York City A Facelift with Polytek Rubbers
                74-45. Once a mold of the original is made, a casting is taken        The Ansonia Hotel in Manhattan is just one of the strikingly
                and the artists meticulously recreate any eroded or missing           ornate buildings that THR has restored. Above, Philip Gallagher
                detail, based on other parts of the original still in good shape,     of THR displays a Poly 74-45 mold that was used to recreate
                historical photographs, etc. Once the master is completed, a          aging architectural brackets from a 13th-floor balcony of the
                mold and perfect reproductions are cast. Since many                   Ansonia Hotel. Cast GFRC replacement brackets in the
                architectural features repeat on a building, a mold such as this      background await installation.
                may be used again & again -- no problem for high-performance



      24
              Polytek          ®


              Development Corp.                                                                                        (610)559-8620 • (800)858-5990
                                                                                             Mold Making Methods                    1
                                                                                         Applications - Home Decor




                                                                                                                                            Mold Making
                                                                                                                                             Methods
  A decorative drapery rod end was cast using EasyFlo 60              A Poly 15-6 plastic column capital is demolded from a TinSil®
  Liquid Plastic (see p. 48), a super low viscosity polyurethane      70-10 silicone rubber mold. This rubber is very soft (Shore
  product, filled with bronze powder to create this faux metal        A10) and stretchy eliminating the need for seams in the mold
  part. The two-piece poured block mold registers nicely due to       to remove cast parts. The shell was made using Poly LiteCast,
  keys/snaps, which keep the mold aligned properly during the         a very low density, pourable polyurethane plastic to reduce the
  casting process. A PlatSil® or TinSil® silicone mold could easily   weight of the shell for easier handling. The column posthole
  produce many dozen resin castings or more without the need          was made by inserting a plastic pipe as a plug in the 70-10
  for release agent.                                                  mold prior to casting.



                                                                              Props, Displays & Special Effects
                         PlatSil Gel-10 was used by Dick Smith                                              Tom Kipp of Studio
                         of FXSmith in Toronto, Canada to                                                   One/Mannetron is shown
                         make hundreds of silicone prosthetic                                               with a hollow, rotocast
                         appliances, which became the scales                                                polyester alien that was
                         worn by Mystique in the blockbuster                                                used as a prop in the
                         movie X-Men. Smith modified PlatSil                                                movie The Roswell
                         Gel-10, a versatile 1:1 mix silicone, so                                           Incident. The casting
                         that it was self-sticking using Polytek's                                          was made in a two-piece
                         PlatSil Deadener. This allowed the                                                 brushed-on Polygel® 40
                         scales to be removed and reapplied for                                             mold. Rotocasting
                         each filming session without adhesives.                                            equipment made by
                                                                                                            Mannetron was used to
 A PlatSil® 71-20 silicone rubber                                                                           create several dozen
 mold was made from a gigantic                                                                              alien figures. Polyvinyl
 fossilized shark tooth to make a                                                                           alcohol was used as a
 museum display item. This two-                                                                             barrier coat and the mold
 piece poured block mold is                                                                                 was washed in a warm
 keyed extremely well with                                                                                  detergent water solution
 snaps and a tongue-and-                                                                                    after several castings to
 groove channel to keep the flashing to a minimum. The                                                      remove styrene buildup in
 casting was made using EasyFlo 120 with 3% PolyColor                                                       the mold, which could
 Black. The liquid plastic was poured into one half of the mold,                                            eventually damage the
 then the mold was closed and supported between two small             mold. This process helped prolong the mold life so that after
 pieces of plywood with rubber bands, and slush-cast by hand          several dozen castings the mold still looked like new!
 to produce a super part in 15 minutes.


                                                                                                                     Polytek            ®

                                                                                                                                            25
www.polytek.com                                                                                                      Development Corp.
              1    Mold Making Methods
              Applications - Concrete
Mold Making
 Methods




                                                   Flexible formliners of every
                                                   size and design are routinely
                                                   created using Poly 74, 75
                                                   and 77-Series Polyurethane
                                                   Liquid Rubbers. These Poly
                                                   rubbers are tough and
                                                   abrasion resistant making
                                                   them ideal for the rigors of
                                                   repeatedly casting large
                                                   concrete parts and panels.
                                                   These formliners can be
                                                   made to reproduce any
                                                   surface texture or design        Cast veneer stones are made by pouring concrete into rubber
                                                   and can be bonded to             gang molds such as this one made from Poly 74-44 polyurethane
                                                   plywood or attached to rigid     rubber. Individual stones can be cast simultaneously into multi-
                                                   supports for precast or cast-    cavity molds then applied to a wall to give the look and feel of
                                                   in-place applications.           real stone. Flexible formliners/molds can be made of entire wall
                                                                                    sections for extremely large projects.



                                                            Poly 75 and 81                                                          Poly 74-45, a
                                                            Series Polyurethane                                                     popular 1:1 mix,
                                                            Liquid Rubbers are                                                      polyurethane liquid
                                                            used to make                                                            rubber, was used to
                                                            concrete stamping                                                       make a paver mold.
                                                            tools and texturing                                                     Pavers cast from
                                                            skins. These                                                            molds made from
                                                            stamping tools are                                                      liquid rubbers have
                                                            made by pouring                                                         much better, life-like
                                                            rubber about ¾-inch                                                     surface detail than
                                                            thick onto a pattern                                                    those made from
                                                            that mimics the                                                         rigid molds owing to
                                                            design that will be                                                     the fact that the
                                                            imprinted to the        liquid rubber flows readily into all available detail on the master
              concrete. Patterns such as slate, brick, irregular flagstone or any   before curing. Hundreds to thousands of concrete parts can be
              custom design including leaves, fossils and much more turns           cast from a single mold depending upon surface texture, proper
              otherwise boring, flat,concrete pathways, driveways and patios        selection of mold rubber and release agent, and careful
              into beautifully colored and textured surfaces.                       demolding.




                                                                                    Polygel® Spray 35 was used to make a mold of this architectural
                                                                                    element. The casting was made from glass fiber reinforced
                                                                                    concrete (GFRC). The Polygel mold was created using a low-
                                                                                    cost (~$4,000) machine designed to automatically meter/mix and
                                                                                    spray the liquid rubber at a 1:1 ratio. The resulting mold is thin
                                                                                    (~3/8-inch thick) so it is very economical and easy to peel away
                                                                                    from complex shapes. Polygel rubber can be brushed for smaller
                                                                                    jobs or sprayed when larger surface area molds are needed.
                                                                                    This mold was sprayed in one continuous process, which took
                                                                                    less than 20 minutes to complete! Polygel Spray 35 cures
                                                                                    enough in 6-8 hours to allow a shell to be applied in the same
                                                                                    day.


      26
              Polytek          ®


              Development Corp.                                                                                         (610)559-8620 • (800)858-5990
                                                                                                 Mold Making Methods                     1
                                                                                                   Applications - Concrete




                                                                                                                                                Mold Making
                                                                                                                                                 Methods
                                                  A decorative                                                       An article in Handy
                                                  concrete                                                           Magazine described
                                                  panel was                                                          how to use Poly 75-
                                                  cast as part of                                                    80 Liquid Rubber to
                                                  a building                                                         make thin, low-cost
                                                  restoration                                                        texturing skins to
                                                  project by                                                         impart a slate
                                                  THR Cast                                                           appearance to flat
                                                  Stone and                                                          concrete. These
                                                  GFRC of                                                            texturing skins were
                                                  Brooklyn, NY.                                                      made by pouring Poly
                                                  A Poly 74-45                                                       75-80 over real
                                                  mold is shown                                                      pieces of slate
                                                  being                                                              (properly sealed and
carefully demolded. The thin poured blanket mold was supported                                                       released). Once the
by a GFRC shell and wood-framed box displayed in the                                                                 first pour gelled, a
background.                                                                                                          second pour was
                                                                                                                     made with slightly
                                                                                                                     less rubber so it didn't
                                                                                                                     quite flow to the edge
                                                      Highway            of the previous pour. Even less rubber was used for the third
                                                      sound              pour done to make a texturing skin that was thicker in the middle
                                                      barriers are       with tapered edges. This allowed the thin cured rubber mats to
                                                      becoming           be overlapped at the edges to make a seamless pattern in the
                                                      more popular       concrete. A thin Poly 75-80 tool is shown being removed from
                                                      to keep traffic    the freshly textured surface. With the use of concrete colors and
                                                      noise from         stains the results are stunning!
                                                      residential
                                                      areas. Poly
                                                                                                                     A Poly Latex 60
                                                      75 Series
                                                                                                                     mold was made to
                                                      rubbers were
                                                                                                                     reproduce this
                                                      used to make
                                                                                                                     concrete angel. The
                                                      flexible
                                                                                                                     mother mold (rigid
formliners with wildlife images to enhance the visual appeal of
                                                                                                                     shell) was made
the standard ribbed wall panel design. Formliner designs
                                                                                                                     from Poly 15-6
incorporating rock, slate, brick, fossil, wood-texture and other
                                                                                                                     Liquid Plastic
architectural and artistic designs are becoming more common as
                                                                                                                     thickened with Poly
architects realize the endless possibilities available when flexible
                                                                                                                     Fiber to make it
molds are used.
                                                                                                                     brushable. The thin
                                                                                                                     blanket mold could
                                                                         also have been made using Polygel® 35 or Polygel 40, high-
                                                 Polygel® Spray 50       performance two part brushable rubbers. Latex rubber is a one-
                                                 was sprayed onto        part mold material, but 15-30 coats of rubber applied over
                                                 this larger-than-life   several days are required to complete the mold. A Polygel mold
                                                 head to make a          can be made in a matter of hours! This Angel blanket mold is a
                                                 thin, yet durable,      one-piece glove mold with no seams, whereas the rigid shell is
                                                 mold. With the          made in several sections to accommodate numerous undercuts.
                                                 right equipment,
                                                 this type of mold
                                                 can be made
                                                 anywhere -- even
                                                                                  If you can pour concrete,
                                                 several stories
                                                 above street level.
                                                                                 you can pour liquid rubber!
                                                                                                                          Polytek           ®

                                                                                                                                                27
www.polytek.com                                                                                                           Development Corp.
              1    Mold Making Methods
              Applications - Prototyping & Model Making
Mold Making
 Methods




              Prototype Parts of All Kinds Made with Polytek Liquid Rubbers & Plastics
              Larami Limited, headquartered in Mt. Laurel,     most cost-effective and release waxes nicely.
              NJ, is the originator and manufacturer of the    Many times plastic parts are the desired end
              internationally-recognized Super Soaker® toy     result, as in the case of a Super Soaker.
              water guns. With engineering and prototype       PlatSil® and TinSil® RTV Silicone Rubbers
              model development facilities in Whitehouse       (see pp. 40-45) are the best choice for casting
              Station, NJ, Larami Limited has been using       polyurethane plastic prototypes. These high-
              Polytek’s mold rubbers, such as PlatSil® RTV     performance silicone rubbers offer the best
              Silicones, and casting plastics, such as Poly    mold life and resistance to damage from
              15-3X, Poly 1512 and Poly-Optic® 1410, very      repeated casting with chemically aggressive
              successfully to create their new products.       liquid polyurethane resins. TinSil 70-25 and
              Producing the Prototype                          70-39 are popular silicone rubbers for             Larami Ltd., originator of the Super
              Many different techniques involving numerous     modelmakers since they are lower-cost, tin-        Soaker®, uses Polytek’s rubber and
              Polytek products are employed in the             catalyzed systems and have hardnesses that         plastic products to make molds and
              production of a unique model or prototype part   makes difficult parts easy to demold. When         castings for various prototyping projects.
              such as the Super Soaker. Master models can      using any tin-catalyzed silicone rubber, be sure
              be carved from wood, sculpted from clay,         to perform a test cure to insure the alcohol       with a super-low mixed viscosity, try
              machined from polyurethane board, wood or        released during the rubber’s cure does not         EasyFlo™ 60 Liquid Plastic (see p. 48).
              plaster using CNC equipment, or created from     interfere with the cure of the polyurethane
              a liquid photopolymer using a stereo-            plastic. If alcohol on the mold surface poses a    Rotational Casting
              lithography process.                             problem, heating the mold to 200°F for several     An additional use of Polytek fast casting
                                                               hours can assist alcohol removal.                  plastics at Larami was to rotationally cast the
              As with any mold making process, it is
                                                               Any PlatSil rubbers can be used for casting        large pressure tank prototype for the Super
              important to determine the most appropriate
                                                               polyurethane plastics. PlatSil 71-20 is an easy    Soaker squirt gun by rotating the hollow tank
              combination of mold making and casting
                                                               1:1 mix, Shore A20 rubber with a super low         mold with a small amount of a Poly Plastic
              materials for the project at hand. If wax
                                                               viscosity and 4-hour demold. For applications      such as Poly 15-3X coating all surfaces as it
              castings are to be made (say for a lost wax
                                                               requiring firmer rubber, PlatSil 71-35, 73-45,     set. Poly 15-3X sets in about 15 minutes at
              process as is used for making many metal
                                                               or 73-60 provide excellent tear and suitable       room temperature, but the silicone rubber
              prototype parts), then a polyurethane mold
                                                               hardnesses. When pouring any one of the            mold was heated to hasten the set and
              rubber such as Poly 74-30 or Poly 74-45 (see
                                                               TinSil or PlatSil rubbers over a model, Pol-       demolding time of the Poly 15-3X resin. All
              p. XX) may be the best choice as they are
                                                               Ease ® 2350 Release Agent (non-silicone)           Poly 15 Series resins can also be accelerated
                                                               should be evaluated as a release.                  with a few drops of Poly 15 Part X
                                                                                                                  Accelerator. See pages 46-56 for more
                                                               Poly Plastics Have Thermoplastic Feel              information on Polytek’s Liquid Plastics and
                                                               The Poly 15-Series products (see p. 49) offer      page 64 for more on rotocasting.
                                                               many types and speeds of cure for almost
                                                                                                                  Water-Clear Poly-Optic® 1410
                                                               every application. Poly 1512 and 1512X are
                                                               most popular for prototypers interested in a       Another Polytek polyurethane plastic used by
                                                               tough, high-performance product with a             Larami is Poly-Optic 1410, a water-clear, low
                                                               thermoplastic feel. It has a 1:1 mix, can be       viscosity resin, which can be used for
                                                               easily colored with PolyColors, has low            transparent parts such as face shields, toy-auto
                                                               viscosity, a fast (5 min) or slow (20 min)         windshields, windows, headlights and eyes.
                                                               potlife, and very impressive physical              Larami Limited can be reached at (856) 439-1717.
                                                               properties when cured. It is non-brittle in thin
                                                               sections and has a high tensile strength. It can     Pressure casting can help
                                                               be sanded, carved, machined or painted as
              PlatSil® 71 and 73 Series mold rubbers           needed. Other 15-Series plastics can be used           prototypes and model
              are widely used for model making and             for lower (Poly LiteCast™, page 54) or higher
              prototyping. This two-piece block mold           density (Poly 15-3X) parts. Poly 15-8 is also         makers create perfect,
              made of PlatSil 71-35 is used to reproduce       available for modelmakers interested in
                                                                                                                      bubble-free castings.
              a thin-walled car model. Prototypers cast        making heat-resistant tools for vacuum-
              dimensionally accurate parts fast using          forming applications. For rapid-casting                    See page 16.
              EasyFlo™ 60 Liquid Plastic (see p. 48).          applications of complex parts requiring a resin



      28
              Polytek           ®


              Development Corp.                                                                                               (610)559-8620 • (800)858-5990
                                                                                             Mold Making Methods                     1
                                                                  Applications - Cast Polyester/Fiberglass Parts




                                                                                                                                              Mold Making
                                                                                                                                               Methods
                                                                              Restoration of the Widener Building in Philadelphia
                                                                              began in the summer of 1990, by Russ Veder, an
                                                                              expert in architectural restoration and principal of
                                                                              American Architectural Art. This project required
                                                                              making detailed flexible rubber molds of the
                                                                              building's ornate Corinthian column capitals, which
                                                                              measure 8 feet by 7 feet with deep 24-inch undercuts.
                                                                              Russ, with subcontractor, Edon Corp., resculpted a
                                                                              fiberglass duplicate of the aged capital to bring it back
                                                                              to its original design. The duplicate was used as a
                                                                              working model to make a Polygel mold that
                                                                              ultimately produced the 10 fiberglass capitals needed
                                                                              for the restoration. Fabric reinforcement was pressed
                                                                              into the wet rubber where needed and soft, flexible
                                                                              foam was pressed into the undercuts to allow the shell
                                                                              to be removed more easily. A final coat of Polygel 40
 Brush-On Polygel® Molds Used to Cast Polyester/Fiberglass Capitals was used to cover the fabric and foam. A fiberglass
 Russ Veder, of American Architectural Art, chose Polygel rubbers because shell was made the following day. Cast fiberglass/
 of their ability to be brushed on easily and capture incredible detail. Edon polyester resin parts were sprayed into the Polygel
 moldmakers Matt Axel and Bob Mathias agreed, "Polygel was the best
                                                                              mold that was coated with a polyvinyl alcohol (PVA)
 mold rubber we ever used. After casting 10 large fiberglass parts, the mold
                                                                              barrier coat to protect the mold from the harsh effects
 was in such good condition, we could have made 50 more."
                                                                              of the polyester resin.




                                                                                Tony Lorino, Capitol Displays of Nashville, TN,
                                                                                uses Poly Latex 60 molds to produce polyester and
                                                                                fiberglass copies of original sculpted models. Poly
                                                                                Latex 60 is the rubber of choice because of it’s
                                                                                durability and ease of application. Being a single
                                                                                component material, Poly Latex 60 is brushed on
                                                                                without the limitation of a pot life. Ten to twenty
                                                                                coats are applied, two per day, to build up proper
                                                                                mold thickness. Gauze is often incorporated into the
                                                                                latex to lend additional strength to large molds.
                                                                                Lorino then builds a rigid polyester and fiberglass
                                                                                mold shell over the latex mold to maintain the shape
                                                                                of the mold during casting. Poly 15-6 and Poly
                                                                                Fiber, or Polygel® Plastic-75 should also be
                                                                                considered for this application. The end result is a
                                                                                lightweight, high tear strength mold with good
                                                                                resistance to the swelling caused by polyester resin.
                                                                                Poly Latex 60 molds allow Capitol Displays to
 Poly Latex for Polyester Fiberglass Parts -- Capitol Displays                  produce detailed parts with undercuts that would be
 Poly Latex 60 was brushed on a sculpted resin model to produce this large      impossible with rigid molds.
 blanket mold for a decorative architectural part.




                                                                                                                     Polytek              ®

                                                                                                                                              29
www.polytek.com                                                                                                      Development Corp.
              1    Mold Making Methods
               Applications - Foam Parts & Shells
Mold Making
 Methods




              Poly 15-3X, 1:1 mix                                                   PolyFoam R-8, a 1:1 by
              polyurethane plastic, was                                             volume, closed-cell foam,
              rotocast to create a thin,                                            makes strong, lightweight
              lightweight, hollow casting.                                          castings quickly. PolyFoam is
              After the 15-3X gelled in ~5                                          mixed and poured into a
              minutes, Poly 15-6                                                    TinSil® or PlatSil® silicone
              polyurethane plastic with 3%                                          rubber mold, which is covered
              (by weight) Part 15F Foamer                                           with a lid to pack the foam to a
              was poured into the hollow                                            higher density for good mold
              15-3X shell while still in the mold. The 15-6/Part F open-cell        fill, thicker skin, and better
              foam expanded to fill the cavity giving the hollow casting support    surface detail. About 20
              without adding much cost or weight.                                   minutes later, parts such as
                                                                                    this plaque or pot can be
                                                 PolyFoam R-5, a 1:1 by             removed from the mold. A barrier coat, such as Barrier PF, can
                                                 volume rigid foam, was used        be applied to the mold to prolong mold life and provide pre-
                                                 to create a very lightweight       primed/painted parts upon demold.
                                                 mold shell to support this
                                                 brushed blanket mold of Poly                                                PolyFoam R-5 and R-8
                                                 74-29 polyurethane rubber.                                                  can be used to easily
                                                 The shell was made by                                                       create parts such as
                                                 pouring liquid PolyFoam R-5                                                 these plaques. Since
              into an unsealed wooden box built around the cured rubber mold                                                 the foams are self-
              that was covered with butcher's wax for release. When the foam                                                 skinning, the plaques
              expanded, it adhered to the box and conformed to the shape of                                                  have all the detail of
              the rubber mold. A little foam goes a long way!                                                                the original.


               Hollow Lightweight Castings
                                                      Poly 1512X, a 1:1 mix,
                                                      pourable, high strength,
                                                      polyurethane liquid plastic
                                                      was mixed with PolyFiber
                                                      thickener to turn the
                                                      pourable plastic into a
                                                      non-sag, thixotropic mix
                                                      that was laid up by hand
              into a Polygel® mold of a boulder. A thin face coat followed by a
              thicker backup coat were applied to create a total thickness of
              approximately ¼ inch. Very little material was needed, so the
              resulting casting was lightweight and low cost. A similar hollow
              casting could have been made using polyester resin and
              fiberglass or glass-fiber reinforced concrete.

              This 10-inch tall head was rotocast using
                                                                                    A poured blanket mold made of Poly 74-20 polyurethane rubber
              just a few pounds of EasyFlo 120, a 1:1
                                                                                    was made from a chainsaw-carved wooden bear to create
              by volume mix, polyurethane plastic that
                                                                                    lightweight duplicates. Notice the thickened seam line in the
              is designed for rotocasting (see
                                                                                    back of the mold that was cut with a mold key knife to permit
              equipment on p. 64) and slush casting,
                                                                                    easy demolding and minimal seam cleanup. Since this mold is
              which is done by hand. If poured solid,
                                                                                    larger, "snaps" or "buttons" were made in the clay blanket which
              this casting would weigh and cost much,
                                                                                    ultimately became part of the rubber mold so the mold would not
              much more. EasyFlo 120 captures all
                                                                                    flop away from the shell while being rotated in the rotocasting
              the detail without thin spots or bubbles.
                                                                                    machine.


      30
              Polytek           ®


              Development Corp.                                                                                      (610)559-8620 • (800)858-5990
                                                                                         Mold Making Methods                   1
                                                                        Applications - Statuary & Figurines




                                                                                                                                      Mold Making
                                                                                                                                       Methods
This 12-inch tall                                                 These frogs were cast in a
sculpture of a                                                    TinSil® 70-25 silicone mold.
mother and child                                                  Each cold cast bronze was
was created by Mary                                               made from EasyFlo 60 with
Smith of Leesport,                                                bronze (mix ratio 1A:1B: 2
PA, and was molded                                                bronze, by volume) and
at a Polytek Seminar                                              finished with a different
& Workshop using                                                  patina for a unique look.
PlatSil® 71-10 Liquid
Silicone Rubber. The
sculpture was                                                     A poured blanket mold was made using PlatSil® 71-20 Liquid
disassembled into                                                 Silicone Rubber, a unique, 1:1 mix, 4-hour-cure system, which
two pieces so that                                                can be used to cast any medium. This gargoyle could now be
the child could be                                                                                             cast in plaster,
molded separately                                                                                              concrete or any
from the mother. The                                                                                           pourable plastic
cold-cast bronze                                                                                               using this PlatSil
figurines were made                                                                                            mold. This blanket
by slushing a thin coating of Poly 1512X mixed with bronze                                                     mold was poured in
powder around the surface of the mold until it gelled. Then a                                                  a single piece, then
dense, low-cost polyurethane plastic (Poly 15-3X) was used as a                                                cut, using a mold
backfill to simulate the weight of a real bronze casting. The                                                  key knife, up both
resulting figurines were glued together using EpoxyBond                                                        sides to create a
adhesive and felt was applied to the bottom. Faux bronze at its                                                mold which opens
best!                                                                                                          like a book.



                                                                                                                   & More!

 The use of Polytek’s liquid mold rubbers                         If you have an application you don’t see
 and casting plastics is not just limited to                      here, call Polytek Customer Service for
 the applications described on the past                           assistance.
 several pages!
                                                                  The use of Polytek materials is limited
          Candle makers                                           only by the imagination -- may yours
          Soap manufacturers                                      be limitless.
          Jewelers
          Taxidermists
          Forensic scientists
          Hobbyists of all kinds
          Inventors
          & many others
 Use Polytek products to make their
 creations.


                                                                                                                Polytek           ®

                                                                                                                                      31
www.polytek.com                                                                                                  Development Corp.
               2    Polyurethane RTV Mold Rubbers


                         Polyurethane RTV Liquid Mold Rubbers
               Polytek offers several Polyurethane RTV Liquid Mold Rubbers
               each formulated to meet various customer applications. Polytek’s            POLYURETHANE MOLD RUBBERS:
               polyurethane mold rubbers consist of a Part A and a Part B that,                    AT A GLANCE
               after mixing, cure at room temperature to flexible, high-strength,
               mold rubbers. Polyurethane rubbers make durable, easy releasing       Poly 74 & 75 Series - Flexible, high-strength mold rub-
Polyurethane
Mold Rubber




               molds for casting plasters and waxes without release agents, but      bers for making tough, durable molds. Polytek’s easiest-
               when used with proper release agents are also excellent for cast-     to-use and bestselling mold rubbers!
               ing cement, epoxy, polyester, urethane and acrylic.
                                                                                     Polygel® Series - Thicken immediately upon mixing
               For many Polytek polyurethane mold rubbers, the last two digits       components making these products exceptional for
               in the product name indicate the approximate Shore A hardness         making brush-on or sprayed blanket molds.
               of the cured rubber. Polytek polyurethane mold rubbers range in
               hardness from a very soft A20 to a very firm D45.                     Poly 77 Series - High elongation mold rubber for maxi-
                                                                                     mum mold life in high volume applications.
               MODEL PREPARATION
               Porous models, such as wood, plaster, stone, pottery or masonry,      Poly 81 Series - Firm rubber for making durable molds
               must be sealed, then coated with a release agent. Multiple coats      or industrial parts or for use in electrical encapsulation
               of paste wax dried and buffed will seal most surfaces. Potters        applications.
               soap can be used as a sealer for plaster. Lacquer, paint, PVA, and
                         ®                                                           Poly 72-40 Series- Flexible rubber that performs well
               Pol-Ease 2350 also work well as sealers for many surfaces.
                                                                                     for casting wax and plaster.
               Models made of sulfur-containing modeling clay (i.e., Roma
               Plastilina) should be sealed with shellac. [CAUTION: When shel-
               lac is used as the sealer, it must be thoroughly coated with         clean metal or plastic mixing container. Then weigh the appro-
               release agent because polyurethane rubbers bond tenaciously to       priate amount of Part A into the same container. Mix thoroughly.
               shellac. In fact, uncoated shellac may be used to bond               Hand mixing with a Poly Paddle (see p. 62) is best to avoid mix-
               polyurethanes to certain surfaces (i.e., plaster).]                  ing air into the rubber. While mixing, scrape the sides and bottom
                                                                                    several times to insure thorough mixing. Pour the rubber as soon
               Non-porous models (i.e., metals, plasticene, wax, glazed ceram-
                                                                                    after mixing as possible for best flow and air bubble release.
               ics, fiberglass, and polyurethanes) and sealed porous models
               should be coated with a release agent such as Pol-Ease 2300.         Vacuum degassing or pressure curing helps to provide bubble
                                                                                    free molds, but is usually not necessary.
               If there is any question about the compatibility between the liq-
               uid mold rubber and the prepared model surface, perform a test       Allow the rubber to cure at room temperature, 77°F (25°C). Heat
               cure on an identical surface to determine that complete curing and   accelerates the cure - low temperatures slow the cure. Avoid cur-
               good release is obtained.                                            ing in areas where the temperature is below 60°F (15°C).
               Porous models must be vented from beneath to prevent trapped         Check product labels or technical bulletins to determine appro-
               air from forming bubbles in the rubber (see p. 12).                  priate cure times. For most polyurethane products, final cure
                                                                                    properties are obtained in about seven days, but most molds may
               MIXING AND CURING                                                    be used with care after curing for 24 to 48 hours.
               Before mixing rubber, be sure that both Parts A and B are at room
                                                                                    USING THE MOLD
               temperature and that all tools and models are ready to go! Check
               product labels or technical bulletins to determine working time      Usually no release agent is necessary when casting plaster or
               for the product -- some products set fast -- meaning that you must   molten wax in polyurethane molds. When casting with plaster,
               work quickly.                                                        sponge, dip, or spray the mold with Pol-Ease Mold Rinse and then
                                                                                    pour plaster on the wet mold to reduce air bubbles in the plaster
               Many Polyurethane Part Bs require stirring before use. If there is   and aid release. When casting resin, spray the mold with Pol-Ease
               a “Stir Before Use” label on the container -- be sure to do so.      2300 Release Agent. For casting concrete, use an appropriate
               Mix Ratios Vary! Check the mix ratios for the specific product       form release such as Pol-Ease 2650 or 2601 Release Agent.
               you are using. For polyurethane rubbers, most mix ratios are         Exposure to solvent-containing form releases should be kept to a
               expressed by weight. Carefully weigh Parts A and B in proper         minimum to reduce likelihood of mold distortion due to shrink-
               ratio. [Note: Polygel products can be mixed 1:1 by weight or vol-    age or swelling.
               ume. See p. 36.]                                                     After repeated casting with certain resins, plaster and cement,
               Weigh Part B (usually the lower viscosity component) into a          molds may shrink slightly since these materials extract oils from
                                                                                    the mold. The proper selection of release agent and/or barrier coat

               Polytek
                                ®


       32
               Development Corp.                                                                                      (610)559-8620 • (800)858-5990
                                                                            Polyurethane RTV Mold Rubbers                               2
can minimize this effect. If shrinkage becomes evident, a light
application of Pol-Ease Mold Dressing can help to restore the
mold to its original dimensions. For more information on the use
of Pol-Ease Mold Dressing, call Polytek Customer Service.

ADDITIVES
Polytek offers various additives that can be used to vary the prop-
erties of the cured and uncured polyurethanes.




                                                                                                                                               Polyurethane
                                                                                                                                               Mold Rubber
•   Softener - For the Poly 74, 75 and 77 Series RTV Liquid
    Mold Rubbers, add Poly 74/75 Part C Softener for a lower
    viscosity mix and a softer cured rubber. Poly 74/75 Part C
    Softener may be added to most other Polytek polyurethane
    mold rubbers except Poly 72-40.
•   Accelerator - For Poly 74, 75 and 77 Series RTV Liquid
    Mold Rubbers, Poly 74/75 Part X can be added to accelerate
    the cure. Poly 74/75 Part X may accelerate other Polytek
    polyurethane mold rubbers. Test on a small scale first.
                                                                        Molds and castings made from Polytek polyurethane products.
                            ®
•   Thickener - Cab-O-Sil Fumed Silica is both a thickener and
    thixotropic agent that can be added to mixed Parts A and B
    in order to form a gel appropriate for application by brush or                 ADDITIVES & ACCESSORIES
    trowel. Cab-O-Sil is only appropriate for use with certain liquid                        Poly 74 Part C Softener
    mold rubber products.                                                             1 pint (1 lb), 1 gal (8 lb), 5 gal (40 lb)
•   UV Stabilizer - Poly UV Additive can be added to mixed                               Poly 74/75 Part X Accelerator
    Parts A and B to improve UV resistance of cured Polytek                                 1 pint (1 lb), 1 gal (8 lb)
    mold rubbers. At 0.5% of the total weight of the liquid mix,
    UV Additive reduces characteristic surface degradation                              Pol-Ease® 2300 Release Agent
    caused by sunlight and other UV sources.                                              12-oz. can, case of 12 cans

•   Colors - Polyurethanes can be tinted to various colors by                           Pol-Ease® 2601 Release Agent
    adding small amounts of PolyColors (see p. 61).                                  1 qt (2 lb), 5 gal (40 lb), Drum (450 lb)
To learn more about additives, refer to product technical bulletins                     Pol-Ease® 2650 Release Agent
or call Polytek Customer Service. Additives and accessories for                     1 qt (1.5 lb), 5 gal (35 lb), Drum (375 lb)
polyurethane mold rubbers are listed in the box to the right.
                                                                                             Pol-Ease® Mold Rinse
CLEAN UP                                                                                          5 gal (40 lb)
Tools should be wiped clean before the rubber cures. Denatured
ethanol is a good cleaning solvent, but it must be handled with                      Poly PVA Solution (Green or Clear)
extreme caution owing to its flammability and health hazards.                              1 qt (2 lb), 5 gal (40 lb)
Work surfaces can be waxed or coated with Pol-Ease 2300                                  Poly Purge™ Aerosol Dry Gas
Release Agent so cured rubber can be removed.                                             10-oz can, Case of 12 cans
SAFETY
                                                                                                   Cab-O-Sil®
Before use, read product labels and Material Safety Data Sheets.
                                                                                                5 gal, 1 bag (10 lb)
Follow safety precautions and directions. Contact with uncured
products may cause eye, skin and/or respiratory irritation and der-                                 Poly Fiber
mal and/or respiratory sensitization. Avoid contact with skin and                                   1 bag (2 lb)
eyes. If skin contact occurs, remove with waterless hand cleaner
or alcohol then soap and water. In case of eye contact, flush with
water for 15 minutes and call a physician. Use only with adequate       ture and, therefore, should be used up as soon as possible after
ventilation. Do not use polyurethane products where food or body        opening. After opening, spray Poly Purge™ Dry Gas Blanket into
contact may occur. Polyurethanes burn readily when ignited.             containers before resealing to displace moist air and extend stor-
STORAGE LIFE                                                            age life.
At least six months in unopened containers stored at room tem-          Polyurethane rubber molds can last many years if stored in their
perature (60-90°F). Parts A and B react with atmospheric mois-          proper shape in a cool, dry location out of direct sunlight.


                                                                                                                           Polytek
                                                                                                                                           ®


                                                                                                                                               33
www.polytek.com                                                                                                            Development Corp.
               2    Polyurethane RTV Mold Rubbers


                     Poly 74 and 75 Series RTV Liquid Rubbers
               DESCRIPTION: Poly 74 and 75 Series Liquid Rubbers consist
               of Part A and Part B that, after mixing, cure overnight at room                     FEATURES
               temperature to flexible, high-strength, mold rubbers. Poly 74 and                   •   Easy-to-use formulations
               75 Series Rubbers make durable, easy releasing molds for casting                    •   Flexible, strong mold rubbers
               plasters and waxes without release agents, but when used with
Polyurethane
Mold Rubber




                                                                                                   •   Reproduce fine details
               proper release agents are also excellent for casting cement, epoxy,
               polyester, urethane and acrylic.                                                    •   Make tough, long-lasting molds
               MODEL PREPARATION: See p. 32.                                               adding 3% Part X (by weight of the total mix) to 74-30 or 74-29,
               MIXING AND CURING: See p. 32.                                               the working time is reduced to approximately 8 minutes -- in the
                                                                                           time it takes to mix the next batch, the previous brushed layer
               USING THE MOLD: See p. 32.
                                                                                           gels enough to apply the next coat. Demolding is possible in as
               ADDITIVES: For general guidelines see p. 33.                                little as 4 hours after the final layer is applied. Rapid curing with
               Softener - For the Poly 74 and 75 Series RTV Liquid Mold                    Part X allows a firm, yet flexible shell or mother mold to be made
               Rubbers, Poly 74/75 Part C Softener can be added to the uncured             in the same day. For example, by adding 1% Part X (by weight
               products for a lower viscosity mix and a softer cured rubber.               of total mix) to Poly 75-80, the working time is reduced to
               When Part C is used, cure time is longer and there is some loss of          approximately 10 minutes and demolding is possible in as little
               strength in the rubber and increased tendency to shrink after               as 6 hours.
               repeated castings. To soften Poly 74-30 to a Shore A15, mix                 Exercise caution when using Part X for poured molds since the
               1A:1B:1C, by weight. The quantity of Part C required to soften              rapid onset of gelling may trap air bubbles on or near the surface
               other products varies and should be determined through experi-              of the master.
               mentation.
                                                                                           Poly 74/75 Part X affects each product differently. Before use,
               Accelerator - For the Poly 74 and 75 Series RTV Liquid Mold                 testing to determine the best amount of Part X to use is advised.
               Rubbers, Poly 74/75 Part X can be added to accelerate the cure.
               Part X is most useful when making brush-on molds with 74-                   CLEAN UP: See p. 33.
               Series rubbers to decrease the time needed between coats. By                SAFETY: See p. 33.


                                                             POLY 74 SERIES PHYSICAL PROPERTIES
                                              74-20            74-29               74-30               74-40              74-44         74-45         74-55
                                                               (74-29 White)       (74-30 Clear)
                Mix Ratio, By Weight          1A:2B            1A:1B               1A:1B               2A:1B              2A:1B         1A:1B         4A:1B
                Hardness, Shore A             20               30                  30                  40                 45            45            55
                Pour Time (min)               30               30                  30                  20                 20            30            15
                Cured Color*                  Yellow           Black               Varies              Varies             Gray          Yellow        Clr Yellow
                                                               (White)             (Clear/Amber)
                Mixed Viscosity (cP)          800              2,800               2,000               3,400              3,500         2,500         4,000
                Specific Volume (in3/lb)      27.5             27.5                27.5                27.5               27.5          27.5          27.5
                Shrinkage Upon Cure           Nil              Nil                 Nil                 Nil                Nil           Nil           Nil

                                                             POLY 75 SERIES PHYSICAL PROPERTIES
                                                   75-59               75-60               75-70                 75-75             75-79                75-80
                Mix Ratio, By Weight              1A:1B               1A:1B                1A:1B                2A:1B             2A:1B                2A:1B
                Hardness, Shore A                     60                  60                  70                    75                80                   80
                Pour Time (min)                       10                  10                  40                    20                20                   45
                Cured Color*                      Amber               Amber                 Gray                Amber      Yellow/Amber         Yellow/Amber
                Mixed Viscosity (cP)               2,500               1,200               3,000                 4,000             2,000                5,000
                Specific Volume, in3/lb               27                  27                  27                    26                26                   26
                Shrinkage Upon Cure                   Nil                 Nil                 Nil                   Nil               Nil                  Nil
                * Some Part Bs darken with age, but cured rubber properties are not affected.



               Polytek
                                 ®


       34
               Development Corp.                                                                                                  (610)559-8620 • (800)858-5990
                                                                            Polyurethane RTV Mold Rubbers                                 2
                                     Poly 74-20 offers the most                                           Poly 74-40 was used to make
                                     remarkable combination of                                            a poured blanket mold of this
                                     tear strength and softness.                                          shelf bracket. The bracket was
                                     With tear strength similar to                                        rotocast using Poly 15-3X
                                     harder rubbers, Poly 74-20                                           polyurethane to make a hollow
                                     pulls away from detail and                                           part that was then backfilled
                                     undercuts with no trouble                                            with Poly 15-6 and Part 15F
                                     at all. Poly 74-20 is great                                          Foamer to give it strength




                                                                                                                                              Polyurethane
                                                                                                                                              Mold Rubber
                                     for casting concrete, plaster                                        while keeping it lightweight
                                     wax and resins.                                                      and low cost.

Moldmaker Chan                                                       A satisfied seminar
Oeur (looking at                                                     attendee displays her
camera) demolds a                                                    cold cast bronze pot
Poly 74-30 brushed                                                   demolded from a two-
mold from one of six                                                 piece, poured block mold
panels created by                                                    made from Poly 74-20.
artist Kate Burke for                                                The keys, which register
the Minnesota                                                        the top and bottom
Veteran’s Home.                                                      halves of the mold,
They sprayed the                                                     worked perfectly to cre-
model with Pol-Ease ®                                                ate a thin, uniform wall
2300 Release Agent,                                                  thickness on the cast
so the separation                                                    part.
was perfectly clean
and trouble-free.




                                                             PACKAGING
                                               Unit Weight                                        Containers
                   Product                         (lb)                         Size                                Net Weight (lb)
                                                                        A                  B                    A                     B
                Poly 74-20                             6               1 qt             2x1 qt                  2.0               4.0
              Mix Ratio :1A:2B                        24               1 gal            2x1 gal                 8.0              16.0
                                                     120              5 gal            2x5 gal                 40.0              80.0
                                                   1,350              55 gal           22x5 gal                450               900
    Poly 74-29, 74-30, 74-30 Clear,74-45               4               1 qt            1 qt                     2.0               2.0
          Poly 75-59, 75-60, 75-70                    16               1 gal          1 gal                     8.0               8.0
              Mix Ratio: 1A:1B                        80               5 gal          5 gal                    40.0              40.0
                                                     900              55 gal      55 gal/11x5 gal              450               450
           Poly 74-40, Poly 74-44                      6              2x1 qt            1 qt                    4.0               2.0
          Poly 75-75, 75-79, 75-80                    24             2x1 gal            1 gal                  16.0               8.0
              Mix Ratio: 2A:1B                       120              2x5 gal           5 gal                  80.0              40.0
                                                     675              55 gal           6x5 gal                 450               225
                                                   1,350             2x55 gal          55 gal                  900               450
                Poly 74-55                             5             2x1 qt             1 pt                    4.0              1.0
              Mix Ratio: 4A:1B                        20             2x1 gal           2x1 qt                  16.0              4.0
                                                     40               5 gal             1 gal                  32.0              8.0
                                                    100              2x5 gal            5 gal                  80.0             20.0
                                                   562.5             55 gal            3x5 gal                 450             112.5


                                                                                                                         Polytek
                                                                                                                                          ®


                                                                                                                                              35
www.polytek.com                                                                                                          Development Corp.
               2    Polyurethane RTV Mold Rubbers

                                           ®
                     Polygel Brushable/Sprayable Mold Rubber
                                                                      U.S. Patent # 5,128,433
                               ®
               USES: Polygel Mold Rubbers are without equal for brushed or
               sprayed blanket molds. Polygel Plastics produce strong, light-             FEATURES
               weight mold shells (see p. 46). Polygel products are ideal for             •    Easy -- 1:1 mix by weight or volume
               molds and shells built up with a brush or spatula on vertical or
Polyurethane
Mold Rubber




                                                                                          •    Excellent for brush-on and spray applications
               overhead surfaces. Evaluate Polygel Mold Rubbers for casting
               plaster, cement and waxes, as well as for limited casting with             •    Fast -- one-day molds
               polyester, epoxy and polyurethane resins. Sprayable Polygel                •    Tough and strong
               products are ideal for large surface area applications where brush-        •    Color-coded mix indication
               ing may be impractical. Polygel products bond well to many sur-
               faces and should be evaluated as adhesives and sealants.                   •    Molds have long library life
                                                                                          •    Good flow into fine detail
               DESCRIPTION: Polygel products consist of liquid Parts A and                •    Good dimensional stability
               B, that after mixing 1:1 by weight or volume, immediately self-
               thicken to a brushable or trowellable consistency. As the liquid      BRUSH-ON MOLDS WITH POLYGEL RUBBER: When
               components of Polygel Mold Rubbers are mixed together, the            brushing Polygel rubber, allow the first coat to gel enough so that
               product changes color and thickens to a buttery, non-sag paste        the second coat will not disturb it (usually about 1 hour is ade-
               with a working time of 1 to 20 minutes (depending on the specif-      quate, 30 minutes for Polygel 35), then apply a second coat being
               ic Polygel product used). A mold can be built up in 2 to 3 coats,     careful to cover any thin spots in the first coat. Do not allow prior
               applied about 1 hour apart. Polygel Spray 35, Spray 50 and Quick      layers to cure completely before applying subsequent coats.
               Spray 50 can be sprayed continuously until the desired mold           Sprayed molds should be made in one continuous application
               thickness is achieved. Polygel rubbers cure overnight at room         without the need for individual layers. Ideally, a blanket mold
               temperature to flexible, tough rubbers. Polygel Spray 35 and          should be at least 1/8-inch thick but not more than 3/8-inch, since
               Quick Spray 50 cure in 4-6 hours.                                     too thick a layer of rubber causes difficulty turning a mold back
               MODEL PREPARATION: See p. 32.                                         on itself during demolding. Allow to cure at room temperature
                                                                                     prior to demolding or building the mold shell. Strength continues
               MIXING AND CURING: See p. 32.
                                                                                     to develop for several days.
                                                                                     REINFORCING BRUSH-ON MOLDS: Rubber molds can be
                                                                                     reinforced with Tietex® Fabric (see p. 61), which is strong and
                                                                                     wets out better than other fabrics. Tietex can be laminated at the
                           Polygel Product Options                                   top of a seam or strips can be laid around the perimeter of a mold
                 Polygel® 35 - Softest, most elastic, brushable Polygel rubber.      to prevent tearing. The fabric may be embedded in the second or
                 Cures to Shore A35 hardness in 4-6 hours.                           third coat of rubber while tacky and covered with a subsequent

                 Polygel® Spray 35 - Sprayable version of Polygel 35
                 designed for use with meter-mix spray equipment.
                 Polygel® 40 - The lowest viscosity mix for best air bubble
                 release and easiest brushing. Cures to a Shore A40 hardness.
                 Polygel® 50 - A thicker mix that cures to a tough Shore A50
                 hardness. Polygel 50 is a great adhesive for repairing
                 polyurethane molds and bonding molds to backing material
                 such as plywood.
                 Polygel® Spray 50 - Designed for spray mold applications
                 using meter-mix spray equipment.
                 Polygel® Quick Spray 50 - A fast, sprayable mold rubber
                 with a 1-minute working time and a 4 to 6-hour cure.
                                                                                     Polygel ® Mold Rubbers are specifically designed for brush-on
                 Polygel® Plastic-75 - See p. 55.
                                                                                     and spray application. After Parts A+B are mixed, they form a
                 Polygel® Shell - See p. 55.                                         thixotropic gel that clings to vertical and overhang surfaces after
                                                                                     application.

               Polytek
                                   ®


       36
               Development Corp.                                                                                        (610)559-8620 • (800)858-5990
                                                                           Polyurethane RTV Mold Rubbers                                        2
                                            Polygel® Spray 50 is                                                                  A large, flexible
                                            applied to a monu-                                                                    rubber dome
                                            mental sculpture with                                                                 mold was made
                                            the VS-3000 Polygel                                                                   quickly using
                                            Sprayer (see p. 64).                                                                  Polygel ® Spray
                                            Using the sprayer, the                                                                50 for the
                                            entire mold was made                                                                  restoration of
                                            in a continuous                                                                       the St. Joseph




                                                                                                                                                          Polyurethane
                                                                                                                                                          Mold Rubber
                                            sprayed piece. The                                                                    County
                                            gel emitting from the                                                                 Courthouse in
                                            sprayer is non-sag                                                                    Southbend, IN.
                                            and, therefore, stays
                                            where it is applied,
                                            but can be moved
                                            around with a brush if                                                                Using Polygel ®
                                            necessary.                                                                            Spray 50 a mold
                                                                                                                                  was made of
                                                                                                                                  this this large
                                                                                                                                  cornice bracket.

coat, which should be as fluid as possible for best penetration of
the cloth. The fabric should not be too close to the model surface
or the weave pattern may show through to the face of the mold.
NOTE ON LAYERING DIFFERENT POLYGEL RUBBERS:
Typically, brush-on molds should be completed with one rubber.
For example, if the face coat is brushed with Polygel 40, then all
subsequent coats should be with Polygel 40. In some cases, the                                                                    This Polygel ®
initial coat can be brushed with lower viscosity Polygel 35 or 40                                                                 mold was used
for better detail and the second (usually final) coat with thicker                                                                to rotocast hol-
Polygel 50 to speed the mold making process. This technique is                                                                    low plaster
acceptable for molds that do not require long-term storage or use.                                                                columns used
When layering different products, oils can transfer from one rub-                                                                 routinely for
ber to another causing warping or curling of the mold. In extreme                                                                 home and office
cases, a mold can distort enough that it will not fit properly into                                                               decor.
its shell.
THICKER MIXES FOR FILLING UNDERCUTS: Polygel
Mold Rubbers can be made even thicker by stirring Cab-O-Sil®
into the mixed Parts A and B.
USING THE MOLD: See p. 32. If a Polygel rubber mold is to
be turned inside out like a sock, the outside surface must be lubri-
cated with soapy water or petroleum jelly so that it slides over
itself easily. The shell or mother mold can be made of Polygel
Plastics, plaster, polyester resin and fiberglass, or Poly 15-6 or
1512X resin filled with Poly Fiber or fiberglass (see p. 61). If the
shell is built with Polygel Plastics or other resin, the rubber must            POLYGEL MOLD RUBBER PACKAGING
be thoroughly coated with paste wax then Pol-Ease 2300 Release
                                                                                                                                    Unit Weight
Agent to prevent the plastic from sticking to the rubber. A plaster    Products
                                                                                                                                      (A+B)
shell must be sealed with potter’s soap, shellac, lacquer or wax to
prevent mold distortion during storage or use.                         Polygel 35 and Polygel Spray 35*                                 4 lb
                                                                       Polygel 40                                                      16 lb
CLEAN UP: See p. 33.
                                                                       Polygel 50, Polygel Spray 50* and Polygel                       80 lb
SAFETY: See p. 33. When spraying Polygel products, use ade-            Quick Spray 50*                                                 900 lb
quate ventilation and personal protective equipment (i.e., respira-
                                                                       * Denotes products sold in 80-lb and 900-lb units only.
tors, gloves, coveralls).

                                                                                                                                 Polytek
                                                                                                                                                      ®


                                                                                                                                                          37
www.polytek.com                                                                                                                  Development Corp.
               2    Polyurethane RTV Mold Rubbers

                                 Poly 77 Series RTV Liquid Rubbers
               DESCRIPTION: Poly 77 Series RTV Liquid Rubbers consist of
               a liquid Part A and Part B that, after mixing, cure at room tem-           FEATURES
               perature to economical, flexible mold rubbers. Consider these              •     High-performance, high-elongation rubbers
               products for casting plasters, cements and waxes. Resins can also
               be cast with proper release agents. The Poly 77 Series has been            •     Hardnesses ranging from Shore A50 to A65
               formulated to provide excellent abrasion and tear resistance for           •     Easy-to-use formulations with 1:1 mix ratios
Polyurethane
Mold Rubber




               maximum mold life and performance. The high elongation char-               •     Easy demolding without damaging molds
               acteristic of these rubbers enables easier demolding and reduces
                                                                                          •     Make tough, long-lasting molds
               mold damage when used in demanding casting applications.
               MODEL PREPARATION: See p. 32.
               MIXING AND CURING: See p. 32.                                                                  PACKAGING
               USING THE MOLD: See p. 32.
                                                                                                       Poly 77-50 and Poly 77-65
               CLEAN UP & SAFETY: See p. 33.                                                            Mix Ratio: 1A:1B (By Weight)

                                 PHYSICAL PROPERTIES                                      Unit Weight                         Containers

                                                       77-50             77-65                  (lb)                 Size               Net Weight (lb)
               Mix Ratio, By Weight                    1A:1B             1A:1B                                 A              B               A       B
               Hardness, Shore A                          50                65                    4           1 qt           1 qt            2.0    2.0
               Pour Time(min)                             15                15                   16          1 gal           1 gal           8.0    8.0
               Color                                     Tan               Tan
                                                                                                 80          5 gal           5 gal      40.0       40.0
               Mixed Viscosity (cP)                    1,200             1,600
                                                                                                900         55 gal          55 gal         450     450
               Specific Volume (in3/lb)                 27.5              27.5




                                 Poly 81 Series RTV Liquid Rubbers
               DESCRIPTION: Use Poly 81 Series rubbers to make firm
               molds, mold facings, stamping tools, industrial parts, rollers, gas-       FEATURES
               kets, mold shells, bumpers or pads. Poly 81 Series rubbers con-            •     Firm rubbers ranging from Shore A90 to D45
               sist of liquid Part A and Part B that, after mixing, cure at room
                                                                                          •     Easy-to-use formulations
               temperature to tough, durable rubbers. They offer low sensitivity
               to moisture, and low viscosity for easy vacuuming, if necessary.           •     Reproduce fine details
               MODEL PREPARATION: See p. 32.                                              •     Make tough, long-lasting molds, tools and parts

               MIXING AND CURING: See p. 32. Parts A and B are clear liq-
               uids. The color of Part B may vary, but it has no effect on cured      USING THE MOLD: See p. 32.
               rubber properties.                                                     CLEAN UP & SAFETY: See p. 33.

                                 PHYSICAL PROPERTIES                                                          PACKAGING
                                                      81-90             81-D45        Product               Unit Weight                 Net Weight (lb)
                                                                                                                  (lb)                  A            B
               Mix Ratio, By Weight               100A:40B            100A:20B
                                                                                      Poly 81-90                 11.2                  8.0          3.2
               Hardness (Shore A/D)                     A90                 D45       (100A:40B)                 56.0                 40.0         16.0
               Pour Time (min)                            23                 19                                 280.0                200.0         80.0
               Demold Time (hr)                           16                 16                                  630                  450          180
               Color                                 Yellow              Varies       Poly 81-D45                 9.6                  8.0          1.6
               Mixed Viscosity (cP)                    2,000              1,600       (100A:20B)                 48.0                 40.0          8.0
                                                                                                                192.0                160.0         32.0
               Specific Volume (in3/lb)                 26.6               26.4
                                                                                                                 540                  450           90


               Polytek
                                 ®


       38
               Development Corp.                                                                                            (610)559-8620 • (800)858-5990
                                                                            Polyurethane RTV Mold Rubbers                                2
             Poly 72-40 Series RTV Liquid Rubbers
DESCRIPTION: Poly 72-40 systems consist of liquid Part A and           USING THE MOLD: See page 32.
Part B that, after mixing in correct ratio, cure at room temperature   Portland cement castings erode the rubber slightly with each cast-
to versatile mold rubbers. They may be poured or thickened and         ing, sometimes leaving a white haze on the cement. Some mold
applied by trowel or brush, to make flexible molds. These molds        releases or barrier coats may reduce mold erosion and whitening
are especially useful for making wax or plaster casts and with         of concrete castings. Repeated contact of the rubber with solvents
release agents are suitable for casting resins and concrete as well.   and oils should be kept to a minimum as these materials will cause




                                                                                                                                              Polyurethane
                                                                                                                                              Mold Rubber
MODEL PREPARATION: See page 32.                                        mold swelling or shrinkage. Spray application of release is best
                                                                       since it minimizes contact with solvents.
CAUTION: Poly 72-40 systems may be subject to cure inhibition
by certain contaminants and may stick to some surfaces. In every       SOFTER MOLDS: Liquid softeners, Poly-Fast 72 Part C and
case where there is any question about the compatibility between       Poly 72 MF Part C, can be added to create rubbers as soft as Shore
the rubber and the prepared surface, perform a test cure on an         A6. Part C should be weighed and thoroughly mixed with the
identical surface to see that satisfactory results are obtained.       proper amount of 72-40 Part B prior to combining with Part A.
                                                                       Each 20 parts C added to 100 parts A+B lowers the hardness by
Poly 72-40 rubber softens some plastics (i.e., styrene) and coat-
                                                                       approximately 10 to 15 Shore A points.
ings (i.e., lacquer). These surfaces must be coated with a barrier
like Poly PVA Solution before applying Poly 72-40.                     CLEAN UP & SAFETY: See p. 33.
MIXING AND CURING: See page 32.                                        STORAGE: Poly 72-40 rubber remains usable for at least 6
                                                                       months from the date of shipment in unopened containers, stored
The proper mix ratio is 1A:10B, by weight, and must be careful-
                                                                       in a cool, dry location. Cured molds slowly soften with age.
ly followed. An error of 5% in the weight of either component can
                                                                       Adequate mixing of components in the proper mix ratio con-
affect the physical properties of the cured rubber and an error of
                                                                       tributes to long mold life as will storage of molds in a dark, cool,
15% can result in a soft, poorly cured rubber. Demold Poly-Fast
                                                                       dry area. With proper care, Poly 72-40 molds should not soften
72-40 after 8 hours at room temperature, 77°F (25°C) and Poly
                                                                       appreciably for 2-4 years. Molds should be discarded before they
72-40 MF after 16 hours. Final cured properties are obtained in 3
                                                                       become too soft to handle. Do not store molds outdoors, as expo-
days. Curing in a warm location, up to 150°F (65°C), accelerates
                                                                       sure to sunlight and excessive humidity will cause rapid deterio-
the cure while low temperatures slow the cure. Avoid curing in
                                                                       ration of the rubber.
areas where the temperature is below 60°F (15°C).
FLOW CONTROL: Cab-O-Sil can be added to produce varying
viscosities in the mixed uncured rubber. Consistencies can range
from that of a thin latex paint to a grease-like putty that can be                     POLY 72-40 ACCESSORIES
buttered onto a vertical surface. Up to 4 parts Cab-O-Sil can be             Poly-Fast 72 Part C, Poly 72 MF Part C Softeners
added to 100 parts of mixed Poly 72-40 Liquid Rubber.                             1 pt (1.0 lb), 1 gal (9.0 lb), 5 gal (45.0 lb)
Part D Liquid Thickener is available for use with Poly 72-40 sys-                           Poly-Fast 72 Part D and
tems. When using Part D, add 1 part D to 100 parts B for a light                         Poly 72 MF Part D Thickeners
cream consistency and 2 parts D to 100 parts B for a grease-like                             (Includes extra Part A)
consistency. Thoroughly stir Part D into Part B before adding Part
                                                                                            1 pt each A + D (2.0 lb)
A. One extra part A must be added for each part D that is used.
When using Part D accurate weighing is essential and careful han-                          0.5 gal each A + D (9.0 lb)
dling is required since it is corrosive.                                                    5 gal each A + D (90 lb)



                  PHYSICAL PROPERTIES                                                           PACKAGING
 Mix Ratio, By Weight                                1A:10B                          Poly-Fast 72-40 and Poly 72-40 MF
                                                                                         Mix Ratio 1A:10B (By Weight)
 Hardness, Shore A                                       40
                                                                         Unit Weight                       Containers
 Pour Time (min)                                         30
                                                                              (lb)                     Size            Net Weight (lb)
 Cured Color                                           Ivory
                                                                                                 A              B         A         B
 Mixed Viscosity (cP)                                 4,000
                                                                                 9.9            1 pt          1 gal      0.9       9.0
 Specific Volume (in3/lb)                                20
                                                                                49.5           1/2 gal        5 gal      4.5      45.0
 Shrinkage Upon Cure                                     Nil
                                                                                495            5 gal          55 gal     45.0     450


                                                                                                                         Polytek
                                                                                                                                          ®


                                                                                                                                              39
www.polytek.com                                                                                                          Development Corp.
              3    Silicone RTV Mold Rubbers

                                             ®
                   Poly-Sil Silicone RTV Liquid Mold Rubbers
              The Poly-Sil® Silicone RTV Liquid Mold Rubbers each consist
              of a Part A and Part B, which, after mixing, cure at room             POLY-SIL® MOLD RUBBERS: AT A GLANCE
              temperature to flexible, high-strength, mold rubbers. Poly-Sil       TinSil® 70 Series - Tin-catalyzed silicone systems that
              Mold Rubbers make molds that are easy releasing and stable at        cure to tough, high-performance rubbers with easy
              higher temperatures. They are excellent for casting plasters,        release properties and resistance to high temperatures.
              waxes, cements, low melting metals and many resins such as           Great for casting polyester resin.
              epoxies, polyesters, urethanes and acrylics.
                                                                                   PlatSil® 71 Series - High-tear strength, platinum-cured
              As with other Polytek elastomers, the last two digits in the
                                                                                   silicone systems with hardness up to A40. Excellent for
              product name indicate the approximate Shore A hardness of the
                                                                                   casting polyurethane resins and dimensionally accurate
              cured rubber. Poly-Sil rubbers range in hardness from a very soft
                                                                                   prototype parts.
              A10 to a firm A60.
                                                                                   PlatSil® 73 Series - High-tear strength, tough, platinum-
Mold Rubber




              MODEL PREPARATION                                                    cured silicone systems with hardness up to A60.
  Silicone




              Porous models such as wood or plaster should be sealed to            Excellent for casting polyurethane foams and
              prevent penetration of the rubber into the pores of the material.    dimensionally accurate prototype parts.
              Wax, petroleum jelly, lacquer, paint and most other coatings are
              suitable sealers. Materials that will contact the rubber can be      PlatSil® Gel 10 - A soft, translucent rubber for delicate
              sprayed or coated with a light coat of Pol-Ease® 2350, which         casting projects and special effects applications
              functions as a sealer and release agent. Allow the Pol-Ease 2350
              to dry before applying liquid rubber. Silicone-based release        Mix Ratios Vary! Check the mix ratios for the specific product
              agents (i.e., Pol-Ease® 2300) are not to be used on surfaces that   you are using. For Poly-Sil rubbers, most mix ratios are
              contact liquid Poly-Sil® rubbers since inhibition and/or adhesion   expressed by weight. Carefully weigh Parts A and B in proper
              may occur. In addition, modeling clays containing sulfur may        ratio. Accurate weighing is essential to obtain optimum physical
              inhibit curing. In every case where there is any question about     properties from the cured rubber. Weigh Part B into a clean
              the compatibility between the rubber and the prepared model         metal or plastic mixing container. Then weigh the appropriate
              surface, a test cure should be made on an identical surface to      amount of Part A into the same container. Mix thoroughly,
              determine that complete curing and good release are obtained.       scraping sides and bottom of the container. Hand mixing with a
              Poly-Sil rubbers may bond to cured silicone rubbers unless a        Poly Paddle (see p. 62) is best to avoid mixing air into the rubber.
              parting agent is used.                                              To ensure a bubble-free mold, deaerate the liquid rubber under
                                                                                  vacuum at 28-29 inches mercury until the mass of rubber rises
              Porous models must be vented from beneath to prevent trapped
                                                                                  and then collapses. Deaerate for an additional 2 minutes. For
              air from forming bubbles in the rubber (see p. 12).
                                                                                  vacuuming, use a mixing container 3 to 4 times larger than the
              MIXING AND CURING                                                   volume of rubber. Pour the rubber as soon after mixing as possible
              Before mixing rubber, be sure that both Parts A and B are at        for best flow and air bubble release.
              room temperature and that all tools and models are ready to go!     If reinforcement of the rubber is needed (i.e., in thin blanket
              Check product labels or technical bulletins to determine working    molds), place stretchy, open mesh nylon or dacron cloth into the
              time for the product -- some products set fast -- meaning that      uncured rubber. Be sure that the fabric is not too close to the
              you must work quickly.                                              mold surface or the weave of the cloth may show through to the
              Many Poly-Sil Part As require stirring before use. If there is a    face of the mold.
              “Stir Before Use” label on the container -- be sure to do so.       Check product labels or technical bulletins to determine cure
              Molds made from high-                                               times. To reach full hardness in the specified demold time,
              performance Poly-Sil ®                                              temperature should be above 77°F (25°C). At lower temperatures,
              rubbers are best for casting                                        more time may be needed to reach full hardness. Curing below
              harsh resins. This gargoyle                                         65°F (18°C) is not recommended. For most Poly-Sil products,
              blanket mold made of soft                                           final cure properties are obtained in about seven days, but most
              PlatSil ® 71-15 easily pulls                                        molds may be used with care after curing for 24 to 48 hours.
              off the cast resin part. The                                        USING THE MOLD
              smooth, release-free                                                No release agent is necessary for casting most materials in Poly-
              demold of silicone is                                               Sil molds. For longer mold life, however, a barrier coat or release
              especially welcome on                                               agent (i.e., Pol-Ease® 2300) is recommended when casting epoxy,
              highly detailed parts.                                              polyurethane or polyester resins. Most Poly-Sil molds can be


      40
              Polytek          ®


              Development Corp.                                                                                      (610)559-8620 • (800)858-5990
                                                                                  Silicone RTV Mold Rubbers                             3
stored for years, but tin-catalyzed silicone molds eventually
deteriorate and lose their elasticity.                                       TINSIL & PLATSIL ACCESSORIES
ADDITIVES & ACCESSORIES                                                               Pol-Ease® 2300 Release Agent
Polytek offers various additives that can be used to vary the                           12-oz can, case of 12 cans
properties of the cured and uncured Poly-Sil rubbers.
                                                                                      Pol-Ease® 2350 Release Agent
    Thinner/Softener - Very low viscosity 50 cSt Silicone Fluid
                                                                                         1 qt (1.5 lb), 5 gal (26 lb)
     can be added sparingly to the mixed rubber to thin the mix
     with some loss of strength, hardness and cure speed. More                                   PlatThix
     than 10% fluid addition may exude from the cured rubber.                         For Thickening PlatSil® Rubbers
    Accelerator - A specially formulated accelerator can be                                   4 oz, 1 pt (1 lb)
     added to most Poly-Sil products to reduce the cure time.                          Silicone Fluid 50 cSt Grade
    Thickener - Specially formulated chemical thickeners can                          For Thinning Poly-Sil® Rubbers
     be added to most Poly-Sil products to make the liquid                          1 qt (2 lb), 1 gal (8 lb), 5 gal (40 lb)
     rubber thicker (i.e., for brush-on application). Cab-O-Sil®                               TinSil® FastCat




                                                                                                                                               Mold Rubber
     Fumed Silica, which is both a thickener and thixotropic                             4 oz, 1 pt (1 lb), 1 gal (8 lb)




                                                                                                                                                 Silicone
     agent, can also be added to mixed Parts A and B in order to
                                                                                                   TinThix
     form a gel appropriate for application by brush or trowel.
                                                                                                4 oz, 1 pt (1 lb)
    Colors - Certain Poly-Sil rubbers can be tinted to various
     shades by adding small amounts of colors.                                          PlatSil® 71/73X Accelerator
                                                                                         4 oz, 1 pt (1 lb), 1 gal (8 lb)
    Barrier Coat - A barrier coat (i.e., Barrier PF) is a fast
     drying, lacquer-like primer that is sprayed into a silicone                           PlatSil® 71R Retarder
     mold and allowed to dry prior to pouring plastic. The                        4 oz, 1 pt (1 lb), 1 gal (8 lb), 5 gal (40 lb)
     plastic cures against the barrier coat and comes out on the                                  Barrier PF
     plastic casting resulting in a pre-primed part. Using a                              1 qt (1.5 lb), 5 gal (35 lb)
     barrier coat may extend mold life.
                                                                                                 Cab-O-Sil®
To learn more about additives, refer to product technical
                                                                                             5 gal, 1 bag (10 lb)
bulletins or call Polytek Customer Service. See additives and
accessories for Poly-Sil products in the box to the right.
CLEAN UP
Tools should be wiped clean before the rubber cures. Denatured
ethanol is a good cleaning solvent, but it must be handled with
extreme caution owing to its flammability and health hazards.
SAFETY
Before use, read product labels and Material Safety Data Sheets.
Follow safety precautions and directions. Contact with uncured
products may cause eye, skin and/or respiratory irritation. Avoid
contact with skin and eyes. If skin contact occurs, remove with
waterless hand cleaner or alcohol then soap and water. In case of
eye contact, flush with water for 15 minutes and call a
physician. Use only with adequate ventilation. Poly-Sil products
are not to be used where food or body contact may occur.
STORAGE LIFE
At least six months in unopened containers stored at room
temperature (60-90°F).

                                                                    Poly-Sil ® rubber blanket molds reproduce the fine details of models
 CAUTION! -- Certain chemicals cause cure inhibition
                                                                    and are soft and tough enough to easily pull off complex castings.
 in silicone rubbers. Beware of amines, polyesters and              Usually, the more intricate the model/casting, the softer the mold
 tin compounds with PlatSil systems. Sulfur                         rubber selected. This very ornate column capital was easily cast
                                                                    in TinSil ® 70-10. The gargoyle mold was made using PlatSil ® 71-
 compounds can affect both PlatSil and TinSil
                                                                    20. The large, multi-piece, Ronald McDonald ® mold was made
 systems. Perform a test cure!                                      using TinSil ® 70-30 to cast numerous polyester resin parts.


                                                                                                                           Polytek         ®

                                                                                                                                               41
www.polytek.com                                                                                                            Development Corp.
              3    Silicone RTV Mold Rubbers
                                                                            ®
                                                             TinSil 70 Series
              DESCRIPTION: TinSil® 70 Series RTV Silicone Rubbers are               ~200°F. This loss of alcohol results in slight shrinkage of the
              condensation-cure, tin-catalyzed, flexible mold rubbers. TinSil       rubber during cure (up to 1%). In cases where slight shrinkage
              products consist of a liquid Part B base and Part A accelerator,      cannot be tolerated, consider PlatSil rubbers.
              which, after mixing at the proper ratio by weight, cure at room       USING THE MOLD: See p. 40. [Note: Molds made with excess
              temperature to rubbers with tough, knotty tear properties. TinSil     catalyst may be subject to faster degradation on aging.]
              molds have easy release properties and high temperature
              resistance. TinSil molds are excellent for casting polyester, epoxy   ACCELERATING CURE SPEED: Use TinSil FastCat in place
              and polyurethane resins, as well as for waxes and other materials     of any TinSil Part A in order to accelerate cure and shorten
              where release-agent-free casting is needed.                           demold time. When using FastCat the working time is shorter, so
                                                                                    care must be taken to avoid over-catalyzing. FastCat can be used
              TinSil 70-10 is the softest system and is used for very delicate      in a range of 2-6 parts per 100 parts B. At 2 parts FastCat to 100
              castings. TinSil 70-25 is Polytek’s most popular and versatile        parts B, the working time and demold time is similar to that
              mid-range hardness silicone rubber. TinSil 70-39 is firm and has      observed when using 10 parts of the appropriate TinSil Part A. At
              excellent tear properties making it popular for casting
Mold Rubber




                                                                                    3 parts FastCat per 100 parts B, the working time is reduced to
  Silicone




              polyurethane forms and plastic prototype parts. TinSil 70-60 is       ~20-30 minutes, with <8 hour demold. Experiment with a small
              stable at higher temperatures making it suitable for casting low      mix first to determine the best amount of FastCat to use. Use of
              melting metals. As a result of its high hardness, TinSil 70-60 has    FastCat can shorten the library life of cured TinSil rubber.
              limited tear strength.
                                                                                    THICKENING FOR BRUSH ON: TinSil 70 Series rubbers can
              MODEL PREPARATION: See p. 40.                                         be thickened with TinThix liquid thickener or with Cab-O-Sil®
              MIXING AND CURING: See p. 40. CAUTION! TinSil products                for brushing on a blanket mold. TinThix is a liquid additive that
              release alcohol while curing. Alcohol can inhibit the surface cure    can be mixed into the Part B (before mixing with Part A) to
              of some polyurethanes. Before casting polyurethanes in a TinSil       achieve varying levels of thixotropy.
              mold, alcohol can be evaporated by letting the mold sit in a warm     ACCESSORIES: See box on p. 41.
              location for 24 hours or by baking the mold for 4 hours at            SAFETY: See p. 41.

                                                                     PHYSICAL PROPERTIES
                                                   70-10               70-20           70-25              70-30            70-39               70-60
              Mix Ratio (By Weight)               1A:10B              1A:10B          1A:10B            2A:100B           1A:10B             5A:100B
              Hardness, Shore A                       10                  20              25                 30               40                  60
              Pour Time (min)                          45                  60              60                 60              45                  30
              Demold Time @ 77°F (hr)                  16                  16              16                 24              16                   24
              Color                                 Blue                Blue            Blue              Beige             Blue                 Red
              Mixed Viscosity (cP)                10,000              10,000          14,000             26,000           25,000              17,000
              Specific Volume (in3/lb)              25.3                25.3            25.3                25.3            21.7                  18
              Specific Gravity                        1.1                 1.1             1.1                1.1            1.27                  1.5
              Shrinkage Upon Cure (%)               ~0.3                ~0.3            ~0.3                ~0.3            ~0.3                 ~0.8

                                                                           PACKAGING
               Product                                      Unit Weight                         Size                            Net Weight (lb)
                                                                    (lb)                 A                 B               A                      B
               TinSil® 70-10, 70-20,                                1.0                4 oz              1 pt             0.1                 0.9
               70-25, 70-39                                         9.0                1 pt             1 gal             0.9                 8.1
               Mix Ratio 1A:10B                                    44.0             1/2 gal             5 gal             4.0                40.0
                                                                   495                5 gal            55 gal            45.0                450
               TinSil® 70-30                                       1.02               1 oz               1 pt            0.02                 1.0
               Mix Ratio 2A:100B                                    8.3               4 oz              1 gal            0.20                 8.1
                                                                   40.8               1 pt              5 gal            0.80                40.0
                                                                  448.8              1 gal             55 gal             8.8                440
               TinSil® 70-60                                       1.05                1 oz              1 pt            0.05                 1.0
               Mix Ratio 5A:100B                                    8.4              1/2 pt             1 gal             0.4                 8.0
                                                                   42.0                1 qt             5 gal             2.0                40.0
                                                                   462                5 gal            55 gal            22.0                440


      42
              Polytek           ®


              Development Corp.                                                                                       (610)559-8620 • (800)858-5990
                                                                                       Silicone RTV Mold Rubbers                         3
                                                            ®
                                          PlatSil 71 Series
DESCRIPTION: PlatSil® 71 Series RTV Silicone Rubbers are
two-component, addition-cure, platinum-catalyzed, flexible mold
                                                                          FEATURES
compounds. The 71 Series products exhibit a tough, knotty tear,           •      Easy mix ratios; some 1:1 mixes available
making them especially valuable to the mold making industry.              •      Cure at room temperature or accelerate with heat
They are excellent mold materials for casting polyester, epoxy            •      Easy release properties -- save on release agents
and polyurethane resins, as well as for waxes and many other
                                                                          •      High tear strength -- fewer prematurely torn molds
materials. PlatSil 71 Series products offer advantages over tin-
catalyzed systems in certain applications because on curing they          •      Good chemical resistance for longer mold life
don’t shrink and don’t produce alcohol (like tin-catalyzed                •      Low/zero shrinkage for better dimensional
silicones) which can inhibit urethane castings.                                  reproduction
MODEL PREPARATION: See p. 40.                                             •      Range of hardnesses from A10 to A40
MIXING & CURING: See p. 40.




                                                                                                                                             Mold Rubber
                                                                      RETARDING CURE SPEED: PlatSil 71R added to PlatSil Part




                                                                                                                                               Silicone
USING THE MOLD: See p. 40.                                            A prior to mixing with Part B slows the cure yielding longer
ACCELERATING CURE SPEED: Accelerate the cure with heat                working time and longer demold time. Adding ~1% of 71R to the
or the addition of PlatSil 71/73X. Mix 71/73X with Part B prior       total mixed weight of PlatSil A+B roughly doubles the working
to adding Part A. Weigh and add Part A to the accelerated Part B      time. Adding ~2% of 71R triples working time. Do not use more
mixture and mix thoroughly. Pour over a properly prepared             than 4% as the system may not cure at all.
model as soon after mixing as possible. The addition of 1 part        THICKENING FOR BRUSH ON: Thicken PlatSil 71 Series
71/73X per 100 parts of Part B decreases the gel time to ~1/3 the     rubbers by adding PlatThix or Cab-O-Sil for brush-on blanket
normal gel time. The addition of 2 parts decreases the normal gel     molds. When brushing PlatSil 71-15 or 71-20, apply subsequent
time to ~1/4. The addition of 3 parts decreases the normal gel        coats to the previous layer within one hour to obtain best adhesion.
time to ~1/6. Experimentation on a small scale is recommended         ACCESSORIES: See box on p. 41.
before making a larger mix.                                           SAFETY: See p. 41.


                                                   PHYSICAL PROPERTIES
                                  71-10             71-15                71-20                 71-30        71-35                71-40
 Mix ratio, by weight           1A:10B             1A:1B                1A:1B               1A:10B        1A:10B                1A:5B
 Hardness, Shore A                  10                15                   20                    30           35                   40
 Pour Time (min)                      5               15                   25                    60           60                   60
 Demold Time (hr) @ 77°F            0.5                 4                    4                   24           24                   24
 Color                             Pink       Blue Green            Lt. Purple             Lt.Green         Blue      Hazy transparent
 Mixed Viscosity (cP)            3,500            15,000               12,000                25,000       15,000               25,000
 Specific Volume (in3/lb)           26              24.7                 24.7                  24.7         24.7                   25
 Specific Gravity                 1.06              1.12                 1.12                  1.12         1.12                 1.10
 Shrinkage Upon Cure                Nil               Nil                  Nil                   Nil          Nil                  Nil


                                                            PACKAGING
 Product                                      Unit Weight                           Size                           Net Weight (lb)
                                                  (lb)                     A                   B               A                  B
 PlatSil® 71-15, 71-20                               2.0                 1 pt                 1 pt           1.0                  1.0
 Mix Ratio 1A:1B                                    16.0                1 gal                1 gal           8.0                  8.0
                                                      80                5 gal                5 gal            40                   40
 PlatSil® 71-10, 71-30, 71-35                        1.0                 4 oz                 1 pt           0.1                  0.9
 Mix Ratio 1A:10B                                    9.0                 1 pt                1 gal           0.9                 8.1
                                                    44.0              1/2 gal                5 gal           4.0                  40
                                                    495                 6 gal               55 gal            45                 450
 PlatSil® 71-40                                      9.8                 1 qt                1 gal           1.7                  8.1
 Mix Ratio 1A:5B                                    48.0                1 gal                5 gal           8.0                   40
                                                    528             2 x 6 gal               55 gal            88                 440

                                                                                                                        Polytek          ®

                                                                                                                                             43
www.polytek.com                                                                                                         Development Corp.
              3    Silicone RTV Mold Rubbers

                                                                            ®
                                                         PlatSil 73 Series
              DESCRIPTION: PlatSil® 73 Series RTV Silicone Rubbers are
                                                                                     FEATURES
              two-component, addition-cure, platinum-catalyzed, high tear
              strength, flexible mold compounds. The 73 Series rubbers are           •      Low viscosity for excellent detail reproduction and
              recommended for evaluation as mold materials for polyester,                   easy degassing.
              epoxy and polyurethane resins, as well as for waxes and many           •      Easy 10A:100B mix ratio -- can use with
              other materials. PlatSil 73 Series silicones offer advantages over            dispensing machines
              tin-catalyzed systems in certain applications because on curing        •      Cure at room temperature or accelerate with heat
              they don’t shrink, they don’t produce alcohol (like tin-catalyzed
              silicones) which can inhibit urethane castings, and they can be        •      Easy release properties -- save on release agents
              heat accelerated to speed the cure.                                    •      High tear strength -- fewer prematurely torn molds
              MODEL PREPARATION: See p. 40.                                          •      Good chemical resistance for longer mold life
                                                                                     •      Low/zero shrinkage for better dimensional
Mold Rubber




              MIXING & CURING: See p. 40.
  Silicone




                                                                                            reproduction
              USING THE MOLD: See p. 40.
                                                                                     •      Range of hardnesses from A30 to A60
              ACCELERATING CURE SPEED: Accelerate the cure with
              heat or the addition of PlatSil 71/73X. Weigh and add 71/73X to      slightly. Remember, heat accelerates the cure; low temperatures
              Part B and mix. Weigh and add Part A to the accelerated Part B       slow the cure.
              mixture and mix thoroughly. Pour over a properly prepared
              model as soon after mixing as possible. Demold when tack free.       THICKENING FOR BRUSH ON: PlatSil 73 Series rubbers
              The addition of 1 part 71/73X per 100 parts of Part B decreases      can be thickened with PlatThix liquid thickener or with Cab-O-
              the gel time to ~35 min. The addition of 2 parts decreases the gel   Sil® for brushing on a blanket mold.
              time to ~30 min. The addition of 3 parts decreases the gel time to   ACCESSORIES: See box on p. 41.
              ~25 min. The addition of 71/73X softens the cured rubber
                                                                                   SAFETY: See p. 41.

                                                                   PHYSICAL PROPERTIES
                                                             73-29                           73-45                               73-60
               Mix Ratio, By Weight                          10A:100B                        10A:100B                            10A:100B
               Hardness, Shore A                             30                              45                                  60
               Pour Time (min)                               45                              60                                  45
               Demold Time @ 77oF (hr)                       16                              16                                  16
               Color                                         White                           Green                               Blue
               Mixed Viscosity (cP)                          15,000                          35,000                              40,000
               Specific Volume (in3/lb)                      25.0                            21.3                                21.3
               Specific Gravity                              1.10                            1.30                                1.30
               Shrinkage Upon Cure                           Nil                             Nil                                 Nil


                                                                                                              PACKAGING
                                                                                                        PlatSil® 73-29, 73-45, 73-60
                                                                                                            Mix Ratio 10A:100B
                                                                                    Unit Weight                           Containers
                                                                                          (lb)                   Size                Net Weight (lb)
                                                                                                                A           B            A         B
                                                                                           1.0               4 oz         1 pt         0.1       0.9
                                                                                           9.0               1 pt        1 gal         0.9       8.1
                                                                                          44.0            0.5 gal        5 gal         4.0      40.0
                                                                                         495 (73-29)        6 gal       55 gal        45.0       450
                                                                                          550               6 gal       55 gal        50.0       500



      44
              Polytek          ®


              Development Corp.                                                                                         (610)559-8620 • (800)858-5990
                                                                                                 Silicone RTV Mold Rubbers                             3
                                                                          ®
                                                   PlatSil Gel-10
DESCRIPTION: PlatSil® Gel-10 is a colorless, translucent,
two-part, liquid, RTV silicone system, that rapidly cures at room                FEATURES
temperature to a soft (~A10), tough rubber within 30 minutes                     •     Soft (~A10), translucent, silicone rubber
after mixing Parts A and B. PlatSil Gel-10 has an easy 1:1 mix                   •     Easy 1:1 mix ratio
ratio.                                                                           •     Fast 30-minute demold with 6-minute work time
PlatSil Gel-10 does not shrink on curing and may be used as a                    •     PlatSil® 71R Retarder slows the cure
flexible mold material for delicate casting projects and to create
                                                                                 •     PlatSil® 71/73X Accelerator speeds the cure
special effects.
                                                                                 •     PlatThix thickens the mix to a brushable paste
MODEL PREPARATION: See p. 40.
                                                                                 •     Bonds to Poly Plastics
MIXING AND CURING: See p. 40. Normal mixes will gel in
approximately 6 minutes at room temperature; faster if warm,
                                                                              THICKENING FOR BRUSH ON: Thicken with PlatThix liquid
slower if cold. Thus, the mix should be immediately placed over




                                                                                                                                                             Mold Rubber
                                                                              thickener or with Cab-O-Sil® for brush-on application. Add 2%




                                                                                                                                                               Silicone
the model or in the mold. There is not normally adequate time for
                                                                              PlatThix to the total mix weight for a light-bodied, non-sag gel.
vacuum (unless retarder is used), but pressure casting may be
useful to eliminate bubbles.                                                  BONDING TO PLASTICS: PlatSil Gel-10 bonds to clean,
                                                                              cured Poly 15 Series plastics that are less than 24-hours old. Poly
Contamination with soaps, amines, sulfur, tin compounds and                   15 Series plastics bond to PlatSil Gel if poured into the PlatSil
some RTV Silicone Rubbers may inhibit surface cure.                           Gel while it is still tacky (less than 30-minutes old). Each bonding
USING THE MOLD: For best results, allow PlatSil Gel-10 to                     procedure should be tested prior to use in production scale.
cure for at least 1 hour before it is put into use. No release agent is       Remember, release agents on any surface can interfere with good
necessary for casting most materials in properly cured PlatSil Gel-           bond development.
10. For longer mold life, however, use a barrier coat or release              ACCESSORIES: See box on p. 41.
agent when casting epoxy, polyurethane or polyester resins.
                                                                              SAFETY: See p. 41.
ACCELERATING CURE SPEED: PlatSil 71/73X can be
mixed into Part B prior to adding Part A to accelerate gel time                                                            David Gavin and
and cure. Weigh and add 71/73X to Part B and mix. Weigh and                                                                colleagues from Arran
add Part A to the accelerated Part B mixture and mix thoroughly.                                                           Studios in Cork, Ireland,
Pour over a properly prepared model as soon after mixing as                                                                proudly display their
possible. Demold when tack free. The addition of 1 part 71/73X                                                             Velociraptor casting made
to 100 parts of Part B decreases the gel time to 1/3 the normal gel                                                        with life-like PlatSil ® Gel-10
time. The addition of 2 parts decreases the normal gel time to                                                             skin.
1/4. The addition of 3 parts decreases the normal gel time to 1/6.
RETARDING CURE SPEED: Adding PlatSil 71R to PlatSil                                                                        PlatSil ® Gel-10 makes
Part A prior to mixing with Part B will slow the cure yielding                                                             great animatronic skins.
longer working time and longer demold time. Adding 71R at 1%                                                               The product can be
of the weight of total mix (A+B) will roughly double the                                                                   softened with the addition
working time. 2% will triple working time. 5% will yield a 60-                                                             of Silicone Fluid and
minute work time with a fast, 120-minute demold time. Never                                                                colored to make the look
use more than 5% since the system may not cure at all.                                                                     and feel just right.

                   PHYSICAL PROPERTIES
                                                                                                        PACKAGING
  Mix ratio, by weight                                   1A:1B                                    Mix Ratio: 1A:1B (By Volume)
  Hardness, Shore A                                      10 + 2                 Unit Weight                            Containers
  Pour time, minimum                                      6 min
                                                                                     (lb)                     Size                 Net Weight (lb)
  Demold time @ 25°C (77°F)                             30 min
                                                                                                        A              B             A            B
  Color                                               Colorless
                                                                                        2.0            1 pt           1 pt          1.0          1.0
  Viscosity, mixed                                   15,000 cP
  Specific volume (in3/lb)                                   25                        16.0            1 gal         1 gal          8.0          8.0
  Specific gravity @ 25°C (77°F)                           1.10                             80         5 gal         5 gal           40           40
  Shrinkage upon cure                                        Nil                       900            55 gal         55 gal         450          450


                                                                                                                                     Polytek             ®

                                                                                                                                                             45
www.polytek.com                                                                                                                      Development Corp.
           4    Casting Plastics/Resins


                                     Casting & Mold Shell Plastics
           Polytek liquid plastics are two-part systems that can be used to
           cast decorative objects, parts, tools, and patterns as well as to cre-            POLYTEK PLASTICS: AT A GLANCE
           ate light-weight mold shells to support brushed or sprayed blan-
           ket molds. Polytek plastics can mimic materials of nearly any                EasyFlo™ Series - Low viscosity, 1:1 mix by volume,
           density and appearance including light-weight foams, thermo-                 fast-setting plastics. Polytek’s easiest-to-use and best-
           plastics, glass, wood, stone and metals. The products can be                 selling plastics!
           poured, layed up or sprayed to accommodate any size casting or               Poly 15-Series - Strong plastics with varying densities:
           object. Varying viscosities, pot-lives, cure times and physical              some are like thermoplastics, others like stone.
           properties allow the user to choose a plastic tailored to their par-
           ticular needs. The versatility of Polytek Plastics is unlimited.             Poly-Optic® 14 Series - Water clear, non-yellowing
                                                                                        casting resins for speciality applications demanding
           MOLD PREPARATION                                                             clear, bubble-free castings.
           Before pouring or applying liquid casting plastics, be sure that the
           surface is properly prepared in order to prevent the plastic from            PolyFoam™ Series - Low viscosity, 1:1 mix ratio, fast-
           sticking or foaming. Polyethylene and silicone rubber molds, such            setting rigid and flexible foams.
           as TinSil® and PlatSil® products, do not require a release agent, but        Poly LiteCast™ - Easy, 1:1 mix ratio plastic with a wood-
           a barrier coat may be helpful. Latex, polyurethane rubber or metal           like density.
           molds must be dry and require a coat of Pol-Ease® 2300 Release
           Agent. A trial casting or application should be made to avoid dam-           Poly Plasti-Flex - Innovative flexible plastic for architec-
           aging a valuable mold and/or wasting liquid plastic.                         tural moldings that bend, props and more.
Casting
Plastics




           When using Poly Plastics to create light-weight mold shells, pre-            Polygel® Plastic-75 - Thickens to a paste upon mixing
           pare the rubber mold surface as described on p. 20. Poly 15-6 and            and cures in 2-4 hours. Makes great mold shells fast.
           Poly 1512X can be mixed with Poly Fiber to thicken the pourable
           plastics to a thixotropic consistency that can be applied to vertical        Polygel® Shell - A sprayable plastic for creating mold
           and horizontal surfaces like frosting a cake. This process is                shells, sprayed-up castings or surface hardcoats.
           described in more detail on p. 22.
                                                                                        Polypoxy® Resins & Poly Cures - Epoxy systems for
           MIXING                                                                       creating various castings including decorative bonded
           Before mixing resins, be sure that both Parts A and B are at room            bronzes and tools that can withstand high heat.
           temperature and that all tools and molds are ready to go! Use
           metal or plastic mixing vessels (i.e., polyethylene pail) and spat-      CURING
           ulas to avoid introducing moisture. Check product labels or tech-
                                                                                    Castings should be allowed to remain in the mold until thorough-
           nical bulletins to determine working time for the product -- some
                                                                                    ly cured. Parts demolded too soon may be subject to deformation.
           products set fast -- meaning that you must work quickly. Some
                                                                                    Use of pre-warmed molds will hasten curing. Mold shells should
           Polytek plastics require stirring before use. If there is a “Stir
                                                                                    not be demolded until fully cured to prevent distortion or warping.
           Before Use” label on the container -- be sure to do so.
                                                                                    Check product labels or technical bulletins to determine appropri-
           Mix Ratios Vary! Check the mix ratios for the specific product           ate demold times. To reach full hardness in the specified demold
           you are using. Carefully weigh/measure Parts A and B in prop-            time, temperature should be above 77°F (25°C). At lower temper-
           er ratio. Accurate weighing/measuring is essential to obtain opti-       atures, more time may be needed to reach full hardness. Curing
           mum physical properties from the cured plastic. Weigh/measure            below 65°F (18°C) is not recommended. For most Polytek plas-
           Part B into a clean metal or plastic mixing container. Then              tics, final cure properties are obtained in within 7 days.
           weigh/measure the appropriate amount of Part A into the same
           container. Mix thoroughly, scraping sides and bottom of the con-         ADDITIVES & ACCESSORIES
           tainer. Hand mixing with a Poly Paddle (see p. 62) is best to avoid      Polytek offers various additives and accessories that can be used
           mixing air into the plastic. Pour mix into mold cavity or apply to       to vary the properties of the cured plastics and/or make using the
           surface as soon after mixing as possible.                                plastics easier.
           Once the containers of Parts A and B are opened, they should be          •     Accelerator/Retarder - Specially formulated chemical accel-
           used completely or resealed tightly as atmospheric moisture can                erators or retarders can be added to Polytek liquid plastics to
           react with the Part A or may cause foaming of the plastic. Poly                vary the cure time.
           Purge™, a dry gas product, can be sprayed into opened containers         •     Fillers - Dry fillers or metal powders can be added to Polytek
           of liquid plastics to lengthen shelf life once opened.                         liquid plastics to vary the density and look of the cured pieces.


           Polytek
                             ®


    46
           Development Corp.                                                                                             (610)559-8620 • (800)858-5990
                                                                                               Casting Plastics/Resins                     4
      Also, fillers can be added to make the liquid plastic thicker        contact with skin and eyes. If skin contact occurs, remove with
      (i.e., for brush-on or trowel application).                          waterless hand cleaner or alcohol then soap and water. In case of
•     Foamer - A chemical foamer can be added to some liquid               eye contact, flush with water for 15 minutes and call a physician.
      plastics to turn them into foams.                                    Use only with adequate ventilation. Polytek plastics are not to be
                                                                           used where food or body contact may occur. Plastics burn readily
•     Colors - PolyColors can be added to liquid plastics (see p. 61).     when ignited. Care should be taken with sanding dust and other
•     Barrier Coat - A barrier coat (i.e., Barrier PF) is a fast drying,   easily ignitable forms of these products.
      lacquer-like primer that is sprayed into a silicone mold and
      allowed to dry prior to pouring plastic. The plastic cures           STORAGE LIFE
      against the barrier coat and comes out on the plastic casting        Polytek liquid plastics can be stored for at least six months in
      resulting in a pre-primed part. Using a barrier coat often           unopened containers stored at room temperature (60-90°F). Cured
      extends mold life.                                                   plastics will last indefinitely, but may discolor as noted above.
To learn more about additives, refer to product-specific technical         In order to maintain dimensions, Poly Plastic mold shells must be
bulletins or call Polytek Customer Service. Additives and acces-           stored in temperatures <100°F. Also, the shells must not be dis-
sories for Polytek plastics are listed in the box to the right.            torted in storage (e.g., no heavy objects placed on top).

FINISHING
Many cured plastics yellow slightly and chalk when exposed to
sunlight and, therefore, should be painted or sealed for exterior              POLYTEK ADDITIVES & ACCESSORIES
use. If they are to be painted or coated, adhesion of the coating
should be checked carefully over a period of time to determine                                 Poly-Optic® 14X Catalyst
that it is satisfactory for the intended use. If all mold release is                               1 oz, 1 pt (1.0 lb)
removed by detergent washing, most oil paints work well.                                      Poly-Optic® 14R Retarder
Castings can be drilled, sanded and machined.                                                       1 pt (1.0 lb)




                                                                                                                                                  Casting
                                                                                                                                                  Plastics
CLEAN UP                                                                                           Part 15X Catalyst
Tools should be scraped clean before the plastic is hard.                                   1 oz, 1 pt (1.0 lb), 1 gal (8.0 lb)
Denatured ethanol is a good cleaning solvent, but it must be han-
                                                                                                   Part 15F Foamer
dled with extreme caution owing to its flammability and health
                                                                                            1 oz, 1 pt (1.0 lb), 1 gal (8.0 lb)
hazards. Work surfaces can be waxed or coated with Pol-Ease
2300 Release Agent so cured rubber can be removed.                                                 Poly UV Additive
                                                                                                    4 oz, 1 pt (1.0 lb)
SAFETY
Before use, read product labels and Material Safety Data Sheets.                                   Bronze Powder
Follow safety precautions and directions. Contact with uncured                             2.0 lb can, 10 lb can, 110 lb can
products may cause eye, skin and/or respiratory irritation. Avoid                                     Cab-O-Sil®
                                                                                                   5 gal, 1 bag (10 lb)
          OTHER SUPPLIERS FOR FILLERS                                                                  Poly Fiber
    3M - Lightweight fillers, Glass Bubbles                                                             2 lb bag
    (800) 541-6752                                                                         Pol-Ease® 2300 Release Agent
    Ball Consulting ltd - Brass, copper and silver powders                                   12-oz can, case of 12 cans
    (800) 225-2673                                                                         Pol-Ease® 2500 Release Agent
    Imerys Inc. (formerly Georgia Marble Co.) - Marble powders                                  (Cleanable/Paintable)
    (888) 277-9636                                                                           10-oz can, case of 12 cans
                                                                                            Pol-Ease® PF Release Agent
    Mahogany Co. - Various fillers
                                                                                              1 qt (2.0 lb), 5 gal (40 lb)
    (609) 625-8101
                                                                                               Barrier PF Barrier Coat
    PQ Corp. - Lightweight fillers, Extendospheres, Q-cells
                                                                                               1 qt (2.0 lb), 5 gal (40 lb)
    (800) 252-0039
                                                                                                     Poly Purge™
    The R.J. Marshall Co. - Aluminum Tihydrate, OnyxFill, etc.                                12-oz can, case of 12 cans
    (248) 353-4100
                                                                                                     PolyColors
    Trelleborg Fillite Inc. - Hollow ceramic mocrospheres                            Red, Green, Yellow, Blue, Brown & Black
    (770) 729-8030                                                                      4-oz bottle (0.25 lb), 1.0 pint (1.0 lb)


                                                                                                                              Polytek
                                                                                                                                              ®


                                                                                                                                                  47
www.polytek.com                                                                                                               Development Corp.
           4    Casting Plastics/Resins

                                  EasyFlo™ Series Liquid Plastics
           DESCRIPTION: EasyFlo™ Liquid Plastics are useful for casting
           decorative objects, production parts, tools, models, patterns, fix-            FEATURES
           tures, duplicate masters and more. Extremely low viscosity pro-                •    Easy 1:1 mix ratio by volume
           vides for excellent detail penetration and the most bubble-free                •    Extremely low viscosity -- pours like water
           castings without employing vacuum degassing and pressure cast-
                                                                                          •    Sets fast with rapid demold
           ing techniques. A rapid demold time makes EasyFlo plastics ideal
           for high volume, fast cast applications. EasyFlo products can be               •    Reproduces finest details
           easily filled for various cold-cast techniques such as cold-cast               •    Tough, non-brittle formula
           bronze, marble, etc. Use EasyFlo 60 when lowest viscosity is
                                                                                          •    Excellent bubble release without vacuum or pressure
           needed for solid pours. EasyFlo 120 is best for rotocasting or slush
           casting to create hollow parts. Both products can be easily color-             •    Readily accepts high filler levels
           cast or painted. Thin-walled castings made from EasyFlo have                   •    Low odor
           surprising strength and lack the brittleness typical of other low vis-
           cosity, fast polyurethane resins.
                                                                                    few drops in a one-pound mix speeds the cure significantly.
           MOLD PREPARATION: See p. 46.
                                                                                    Exotherm (heat of reaction; see p. 6) and thus shrinkage on cooling
           MIXING: Measure equal volumes of A and B into a mixing con-              is increased. Experiment to determine the right amount of Part X to
           tainer such as a polyethylene pail. Mix immediately and thor-            use, but never use more than 1% Part X of the total weight of the
           oughly for one minute. See p. 46 for more information.                   mix or the final physical properties may be affected.
           CURING: See p. 46.                                                       Fillers should be added after A and B are mixed. Microballoons can
                                                                                    be added to create a wood-like, lower density material. Bronze
Casting
Plastics




           ADDITIVES: Part 15X Catalyst can be used with EasyFlo prod-
           ucts. Part 15X should be stirred into the Part B before adding Part      powder, calcium carbonate, fly ash, sand, granite or other stone-
           A. Part X is a powerful catalyst to increase the speed of curing. A      like fillers can be added as desired. It is imperative that any filler
                                                                                    be thoroughly dried before mixing with resin.
                                                                                    PolyColors (see p. 61) can be added to EasyFlo Part B before mix-
                               PHYSICAL PROPERTIES                                  ing with Part A to create plastic of any color desired.
            Mix Ratio, By Volume                                         1A:1B
                                                                                    FINISHING: See p. 47.
            Mix Ratio, By Weight                                     100A:90B
            Hardness, Shore D                                                 65    CLEAN UP: See p. 47.
            Pour Time (min), 1-lb mix (faster with 15X)                  2 - 2.5    SAFETY: See p. 47.
            Demold time (min) (faster with 15X)                           15-30
            Specific Gravity (mixed)                                       1.03                                             These bronze castings were
            Color, Cured                                                  White                                             created quickly and easily by
            Initial Mixed Viscosity (cP) EasyFlo 60                           60                                            mixing bronze powder with
                                         EasyFlo 120                        120                                             EasyFlo™ 60 Liquid Plastic.
            Specific Volume (in3/lb)                                       26.9                                             Large castings such as this
            Maximum Exotherm             EasyFlo 60               230°F (110°C)                                             10-inch tall Zeus head can be
                                         EasyFlo 120               200°F (94°C)                                             rotocast with EasyFlo 120 to
                                                                                                                            create hollow parts weighing a
                                                                                                                            fraction of the weight of solid
                                     PACKAGING                                                                              castings.
                              Mix Ratio: 1A:1B (By Volume)                                                                     EasyFlo™ 60 castings of
             Unit Weight                             Containers                                                                decorative molding were
                                                                                                                               cast in a PlatSil® 71-35
                  (lb)                      Size             Net Weight (lb)
                                                                                                                               mold. EasyFlo can be eas-
                                      A              B            A          B                                                 ily colored with PolyColors
                   3.8               1 qt           1 qt          2.0       1.8                                                (see p. 61) or mixed with
                 15.2               1 gal          1 gal          8.0       7.2                                                dry fillers such as sand,
                   76               5 gal          5 gal          40        36                                                 aluminum trihydrate, mar-
                                                                                                                               ble powder and more.
                  855              55 gal          55 gal     450          405


           Polytek
                             ®


    48
           Development Corp.                                                                                            (610)559-8620 • (800)858-5990
                                                                                                     Casting Plastics/Resins                      4
                           Poly 15 Series Liquid Plastics
DESCRIPTION: Poly 15 Series Liquid Plastics are excellent for
casting decorative objects, production parts, tools, models, pat-                   FEATURES
terns, fixtures, duplicate masters and more. Poly 15-6, 1510, 1512                  •     Easy -- 1:1 mix ratio formulations
and 1512X have the feel and density of thermoplastics. Poly 15-3
                                                                                    •     Reproduces fine details
and 15-3X resemble stone. Poly 15-8 is an aluminum-filled sys-
tem that is ideal for applications where heat resistance and thermal                •     Can be machined, drilled, sanded
conductivity are required (i.e., vacuum forming). Poly 1512 Clear                   •     Tough and hard, but not brittle
is designed for casting transparent parts, but yellows with age. For
                                                                                    •     Long life for molds and shells
applications requiring water-clear, non-yellowing plastics, consid-
er Poly-Optic® products.                                                            •     Low shrinkage upon cure

MOLD PREPARATION: See p. 46.                                                        •     Air bubbles rise and break

MIXING: See p. 46.                                                                  •     Long working time or instant set with 15X
                                                                                    •     Low odor formula
CURING: See p. 46.
                                                                                    •     Castable in large masses
ADDITIVES: Part 15X Catalyst is a powerful catalyst to increase
the speed of curing. Part X should be stirred into the Part B before
adding Part A. A few drops in a one-pound mix speeds the cure                density material. Bronze powder, calcium carbonate or other dry
significantly. Exotherm (heat of reaction; see p. 6) and thus shrink-        fillers can be added as desired. Fillers should be added after A and
age is increased. Experiment to determine the best amount of Part            B are mixed. It is imperative that any filler be thoroughly dried
X to use, but never use more than 1% Part X of the total weight of




                                                                                                                                                       Casting
                                                                                                                                                       Plastics
                                                                             before mixing with resin.
the mix or the final physical properties may be affected.
                                                                             PolyColors (see p. 61) can be added to some 15 Series Part Bs
Part 15F Foamer can be added to Poly 15-6 and 1510 to create                 before mixing with Part A to create colored plastics.
rigid, open-cell foams with densities as low as 6 lb/ft3. Part F             FINISHING: See p. 47.
Foamer should be stirred into the Part B before adding Part A.               STORAGE: In order to maintain dimensions, Poly Plastic mold
Experiment to determine the best amount of Part F for the appli-             shells must be stored in temperatures <100°F. Also, the shells
cation at hand, but never use more than 3% Part F of the total               must not be distorted in storage (e.g., no heavy objects placed on
weight of the mix or the final physical properties may be affected.          top). See p .47.
For self-skinning foams, consider PolyFoam™ products (see p. 53).
                                                                             CLEAN UP: See p .47.
Poly Fiber can be added to thicken the mix to a paste-like consis-
                                                                             SAFETY: See p. 47.
tency. Microballoons can be added to create a wood-like, lower

                                                           PHYSICAL PROPERTIES
                                    15-3/15-3X                  15-6              15-8                1510        1512/1512X      1512 Clear
 Mix Ratio (By Weight)                   1A:1B                 1A:1B         26A:100B                1A:1B              1A:1B           1A:1B
 Hardness, Shore D                           80                   72                80                  71                  71               80
 Pour Time, 1-lb mix (min)            15 (15-3)                    5                30                  19          22 (1512)                17
                                      5 (15-3X)                                                                     5 (1512X)
 Maximum Exotherm, 1-lb mass        122°F (50°C)          203°F (95°C)     131°F (55°C)       264°F (129°C)       251°F (122°C)   251°F (122°C)
 Demold Time (hr)                     12 (15-3)                   1-3             1-16                1-16        1-16 (1512)             1-16
   (varies with 15X)                  1 (15-3X)                                                                   0.5 (1512X)
 Specific Gravity                          1.53                  1.08              1.57               1.08                1.10            1.10
 Color, Cured                               Tan                   Tan             Gray           Off-White              White Clear/Pale Yellow
 Viscosity, 2-min after mix (cP)          2,000                   800            6,000                 160                 400             300
 Specific Volume (in3/lb)                    18                    26             17.6                  26                25.1            25.1
 Shrinkage Upon Cure (in/in) 0.0002* (15-3)                    0.003*           0.0002           Very low*          Very low*        Very low*
                                 0.008* (15-3X)
 *Shrinkage is primarily caused by gelling while hot then cooling. Parts that cure with minimal temperature rise exhibit minimal shrinkage.



                                                                                                                                   Polytek
                                                                                                                                                   ®


                                                                                                                                                       49
www.polytek.com                                                                                                                    Development Corp.
           4    Casting Plastics/Resins

                                                                                                                      Polytek ® is proud to
                                                                                                                      share its hometown,
                                                                                                                      Easton, PA, with
                                                                                                                      Crayola Inc. The larger-
                                                                                                                      than-life crayons falling
                                                                                                                      from the roof of the
                                                                                                                      Crayola Factory Visitors
                                                                                                                      Center were cast in
                                                                                                                      Poly 15-6 Liquid Plastic.




           Mother Earth Float in Macy’s 74th Annual Thanksgiving Day
           Parade was hard-coated with Poly 1512X Liquid Plastic to create
           a tough, paintable surface. The float, sponsored by Maytag
           Neptune Washer, was built at Macy’s Parade Studio.


                                                                                                                      Numerous fillers can
                                                                                                                      be added to Poly 15
Casting
Plastics




                                                                                                                      Series Liquid Plastics
                                                                                                                      to create castings with
                                                                                                                      varying looks and den-
                                                                                                                      sities.




           Poly 15 Series Liquid Plastics reproduce the finest detail.




                                                                 15 SERIES PACKAGING

                                                             Unit Weight                               Containers
                                Product                          (lb)                 Size                             Net Weight (lb)
                                                                               A                 B                   A                 B
                          Poly 15-3, 15-3X                           5       1 qt              1 qt                  2.5                2.5
                          Mix Ratio 1A:1B                           20       1 gal             1 gal                10.0               10.0
                                                                   100       5 gal             5 gal                50.0               50.0
                       Poly 15-6, 1510, 1512,                        4        1 qt              1 qt                 2.0               2.0
                        1512X, 1512 Clear                           16        1 gal            1 gal                 8.0               8.0
                          Mix Ratio 1A:1B                           80        5 gal            5 gal                40.0              40.0
                                                                   900       55 gal          11 x 5 gal             450               450
                             Poly 15-8                             3.2       1 pt              1 qt                  0.7               2.5
                        Mix Ratio 26A:100B                        12.1       1 qt              1 gal                 2.5               9.6
                                                                  48.5       1 gal             5 gal                10.0              38.0


           Polytek
                            ®


    50
           Development Corp.                                                                                  (610)559-8620 • (800)858-5990
                                                                                                      Casting Plastics/Resins                    4
                                        ®
      Poly-Optic 14 Series Clear Casting Resins
DESCRIPTION: Poly-Optic® 14 Series Casting Resins are useful
for casting decorative objects, production parts, models and more.                   FEATURES
Poly-Optic 14 Series polyurethanes are two-component systems                         •      Crystal clear like water
that were formulated specifically for applications where optical
                                                                                     •      Low viscosity for easy pouring
clarity is a must. Castings are clear like water; however, dyes can
be added to obtain clear, colored castings. Poly-Optic systems,                      •      Reproduces fine details
with their low viscosities and long pot-lives, provide for easy mix-                 •      1410 and 1420 can be machined, drilled, sanded
ing, excellent detail penetration and easy degassing resulting in                    •      Long working time
bubble-free castings when vacuum or pressure casting techniques
                                                                                     •      Low shrinkage upon cure
are employed.
Poly-Optic® 1410 cures to a hard plastic that is virtually
unbreakable. Poly-Optic 1410 can be cured at room temperature                 the total mix). One fifth of total mix times 3 equals the amount of
and, for optimum physical properties, post cured at 150°F (65°C).             Part A required. One fifth of the total mix times 2 equals the
                                                                              amount of Part B required.
Poly-Optic® 1420 cures to a tough, impact- and heat-resistant
plastic that can be polished and machined. Poly-Optic 1420 must               VACUUM DEGASSING OR PRESSURE CASTING: For
be heat cured at temperatures between 150-180°F (65-80°C) to                  bubble-free Poly-Optic castings, vacuum degassing or pres-
obtain strength. If brittle, glass-like castings are desired, heat cur-       sure casting must be employed. When using vacuum for
ing is not necessary.                                                         degassing, it is best to degas Part B before mixing and then degas
                                                                              again after mixing A and B. A light spray of Pol-Ease 2300 or
Poly-Optic® 14-70 is a firm rubber. Blends of Poly-Optic 1410




                                                                                                                                                        Casting
                                                                                                                                                        Plastics
                                                                              quickly passing the flame of a torch over the back of the casting
and 14-70 allow any hardness between Shore D85 and Shore A70.
                                                                              will help break any bubbles on the back of the pour. See p. 16 for
MOLD PREPARATION: For optically clear castings, use highly                    more information on these techniques.
polished molds such those made from shiny polyethylene or
                                                                              CURING: Poly-Optic 1410 and 14-70 cure at room temperature.
polypropylene or PlatSil molds made from polished masters. See
                                                                              For castings less than 0.5-in thick, use Part 14X, or for best results
p. 43 for more information.
                                                                              cure 8 hours or more at 140-150°F. Failure to follow these instruc-
[Caution! Molds made from TinSil® 70 Series rubbers are not rec-              tions may result in tacky and/or soft parts. Castings greater than
ommended for casting Poly-Optic since residual alcohol can                    0.5-in thick do not require heat or 14X, but the use of either will
inhibit the cure or result in hazy castings.]                                 speed up the curing process considerably. Recommended cure for
MIXING: See p. 46 for information on proper mixing.                           Poly-Optic 1420 is 8 hours at 150°F and for optimum physical
The table below provides mix ratios and the following example                 properties 16 hours at 150°F. Poly-Optic 1420 may be demolded
shows how to apply the mix ratios. To calculate the proper                    sooner when cured at a higher temperature such as 30 minutes at
amounts of Parts A and B for Poly-Optic 1410, first determine the             175°F depending on size of casting and mold.
total weight of resin required and divide by 5 (equals one fifth of           See p. 46 for additional information on curing.


                                                           PHYSICAL PROPERTIES
                                                    Poly-Optic® 1410                     Poly-Optic® 1420              Poly-Optic® 14-70
 Mix Ratio (By Weight)                              3A:2B (100A:67B)                     2A:1B (100A:50B)              4A:5B (100A:125B)
 Hardness (Shore A or D)                            D85                                  D85                           A70
 Pour time (min), 2-lb mix                          15                                   15                            15
 Maximum exotherm, 2-lb mass                        265°F (129°C)                        311°F (155°C)                 190°F (88°C)
 Demold time (hr)                                   2 (1-in thick casting)*              8 @150°F (65°C)               24-48
                                                                                         0.5 @175°F (79°C)
 Specific gravity                                   1.07                                 1.05                          1.06
 Viscosity, 2 min after mixed (cP)                  700                                  250                           336
 Specific Volume, in3/lb                            27.5                                 27.5                          27.5
 Shrinkage Upon Cure                                Very low**                           Very low**                    Very low**
 * Demold time for Poly-Optic 1410 and 14-70 varies with thickness of casting and the amount of Part 14X added.
 ** Shrinkage is caused primarily by gelling while hot then cooling. Parts that cure with minimal temperature rise exhibit minimal shrinkage.



                                                                                                                                    Polytek
                                                                                                                                                    ®


                                                                                                                                                        51
www.polytek.com                                                                                                                     Development Corp.
           4    Casting Plastics/Resins

                                                         POLY-OPTIC® 14 SERIES PACKAGING

                                                               Unit Weight                                     Containers
                                 Product                           (lb)                        Size                              Net Weight (lb)
                                                                                      A                  B                   A                     B
                                      ®
                           Poly-Optic 1410                         10.0            3 x 1 qt           2 x 1 qt               6.0               4.0
                           Mix Ratio 3A:2B                         60.0             5 gal             3 x 1 gal             36.0              24.0
                                      ®
                           Poly-Optic 1420                          6.0            2 x 1 qt            1 qt                  4.0               2.0
                           Mix Ratio 2A:1B                         24.0            2 x 1 gal           1 gal                16.0               8.0
                                                                  120.0            2 x 5 gal           5 gal                80.0              40.0
                                      ®
                          Poly-Optic 14-70                         14.4              1 gal             1 gal                 6.4               8.0
                           Mix Ratio 4A:5B                         72.0              5 gal             5 gal                32.0              40.0


           ACCELERATING CURE SPEED: Mix Poly-Optic 14X
           Catalyst into Part B prior to adding Part A to accelerate the gel and
           cure time for Poly-Optic resins. 14X is recommended for castings
           less than 0.5-in thick. For best results, mix Parts A and B, degas if
           required, then add 14X and degas again if necessary. Adding 0.5%
           14X to the total mix weight speeds the cure significantly. For
           example, 0.5g 14X in a 100g mix of Poly-Optic 1410 halves the
           pour and cure time. Exotherm (heat of reaction; see p. 6) and thus
Casting
Plastics




           shrinkage on cooling is also increased. Experiment to determine
           the best amount of 14X to use, but do not use more than 1% 14X
           because final physical properties may be affected.
           RETARDING CURE SPEED: Poly-Optic 14R Retarder slows
           the cure of Poly-Optic systems. Slowing the cure also reduces
           exothermic heating that can cause distortion, waviness and shrink-
           age especially in castings >½-inch thick. Adding 1.5% 14R to the
           total mix weight of Poly-Optic 1410 increases pot-life from 15          The clarity of Poly-Optic® 1410 is remarkable. This amazing neg-
           minutes to 70 minutes. Depending on the size and mass of the            ative sculpture comes to life with overhead lighting.
           part, post curing Poly-Optic 14-70 and 1410 parts in the mold at a
           minimum of 140°F for 12 to 16 hours may be necessary. The
           extended pot-life creates a lower exotherm upon curing, allowing
           larger castings to be made without distortion. Never use more than
           4% since the system may not cure properly.
           COLORS: Add PolyColors (see p. 61) to 14 Series Part B before
           mixing with Part A to create clear plastics of any color.
           EXTERIOR USES: Although Poly-Optic 1410 and 1420 are
           non-yellowing formulas, they are not recommended for long-term
           exterior use. Poly UV Additive can be added to improve durabil-
           ity for exterior applications. Adding 1% UV Additive to the total
           mix weight of Poly-Optic reduces the onset of chalking and pit-
           ting of the outside surface for ~2 years. Adding 3% Poly UV
           Additive can result in good exterior stability beyond 5 years.
           CLEAN UP: See p. 47.
           SAFETY: See p. 47.
           STORAGE LIFE: At least six months in unopened containers
           stored at room temperature. Poly-Optic 14 Series Part As may            Poly-Optic® 1410 Liquid Plastic was poured into a cylindrical
           crystallize slightly or become viscous during storage. If crystal-      mold to form a rod, which was softened in hot water and coiled
           lization occurs warm the container to 100-120°F until crystals dis-     around a mandrel. Once cooled, it holds its shape to form a
           sipate. Cool to room temperature before use.                            tough, spring-like coil.


           Polytek
                             ®


    52
           Development Corp.                                                                                          (610)559-8620 • (800)858-5990
                                                                                            Casting Plastics/Resins                        4

                   PolyFoam™ Series Casting Foams
DESCRIPTION: PolyFoam™ Series Casting Foams consist of liq-
uid Parts A and B that, after mixing, form self-skinning foams.              FEATURES
PolyFoam can be used to cast rigid or flexible objects with densi-           •   Easy 1:1 mix ratios
ties in the range of 8-20 lb/ft3. Considered PolyFoam for produc-
                                                                             •   Self-skinning foams
tion of decorative objects, light-weight mold shells, production
parts, tools, models, patterns, fixtures, duplicate masters and gen-         •   Rigid and flexible foams
eral tooling use. PolyFoam systems do not contain toluene diiso-             •   Densities range from 8 to 20 lb/ft3
cyanate, MOCA, heavy metals or HCFCs, and are practically
odorless. PolyFoam R-5 and R-8 are rigid foams. PolyFoam F-5 is
flexible for casting soft parts.                                       the mold until thoroughly cured. Parts demolded too soon may be
                                                                       subject to deformation. For best casting results, the mold should
MOLD PREPARATION: See p. 46. Be sure that rubber molds                 be warmed to between 75°F and 85°F prior to casting the first part.
used with PolyFoam are stiff enough so as not to distort when sub-     Once a mold is heated and cycled, it will maintain heat for con-
jected to packing pressures.                                           tinued production.
A suitable barrier coat such as Barrier PF can help to extend mold     FINISHING: See p. 47 for general guidelines. When casting rigid
life when using rigid foams. If Barrier PF is used, Pol-Ease® PF       foams, the use of an appropriate primer/barrier coat, such as
Release Agent should be applied to the mold prior to applying          Barrier PF, sprayed and allowed to dry in the mold before casting
Barrier PF.                                                            will result in a pre-primed part upon demolding.
MIXING: See p. 46 for general guidelines. Combine Parts A and          CLEAN UP: See p. 47.
B and mix immediately with a Turbo mixer or other high speed




                                                                                                                                               Casting
                                                                                                                                               Plastics
                                                                       SAFETY: See p. 47.
mixer for 30 seconds. Pour mix into cavity as quickly as possible
since foaming starts immediately. If too much time elapses, the
foam will rise in the mixing container and the mix may be lost.                          PHYSICAL PROPERTIES
Once the containers of Parts A and B are opened, they should be                                          PolyFoam™           PolyFoam™
used or resealed tightly as atmospheric moisture contamination                                            R-5/R-8                F-5
may degrade product integrity causing excess foaming, pressure
                                                                        Mix Ratio                           1A:1B              1A:1B
build up and poor cure properties. To improve shelf stability of
                                                                                                     (By Weight or Volume)   (By Weight)
the liquid products, use Poly Purge to displace moist air in opened
A and B containers before resealing.                                    Mix Viscosity (cP)                  1100                1400
                                                                        Cream Time (sec)                     45                   45
CURING: Packing PolyFoams to a minimum of 2-3 lb/ft3 above
                                                                        Rise Time (min)                       2                   3-5
their free-rise density is recommended to achieve good surface
detail and mold fill. A lid with small vents to allow air to escape     Tack-Free Time (min)                  3                   25
as foam rises should be firmly clamped in place prior to rise. Once     Demold Time (min)                   10-15               30-60
foam begins rising, avoid stirring or other movement that will          Free-Rise Density (lb/ft3)     5 (R-5), 8 (R-8)            5
cause cells to collapse. Castings should be allowed to remain in        Molded Density (lb/ft3)             8-20                 8-15



                                                             PACKAGING
                                                 Unit Weight                                      Containers
                   Product                           (lb)                        Size                               Net Weight (lb)
                                                                         A                 B                    A                     B
                       ™
            PolyFoam R-5, R-8                        4.0                1 qt              1 qt                  2.0               2.0
              Mix Ratio 1A:1B                       16.0                1 gal             1 gal                 8.0               8.0
           (By Weight or Volume)                      80                5 gal             5 gal                 40                40
                                                    900                55 gal            55 gal                450               450
               PolyFoam™ F-5                         4.0                1 qt              1 qt                 2.15              1.85
               Mix Ratio 1A:1B                      16.0                1 gal             1 gal                 8.6               7.4
                 (By Weight)                          80                5 gal             5 gal                  43                37
                                                    900                55 gal           11x5 gal               484               416


                                                                                                                          Polytek
                                                                                                                                           ®


                                                                                                                                               53
www.polytek.com                                                                                                           Development Corp.
           4    Casting Plastics/Resins


                                      Poly LiteCast™ Liquid Plastic
           DESCRIPTION: Poly LiteCast™ Liquid Plastic has a wood-like
           density and can be used to produce decorative objects, tools, mod-          FEATURES
           els, patterns, fixtures and duplicate masters. Poly LiteCast repro-         •       Wood-like density
           duces fine details from molds and can be drilled, sanded and                •       Easy 1:1 mix ratio by weight or volume
           machined.                                                                   •       Safe and easy to machine, contains no silica
           MOLD PREPARATION: See p. 46.                                                •       Tough and hard, but not brittle
           MIXING AND CURING: See p. 46. [Note: Stir both Parts A and
           B before use since the filler in Poly LiteCast rises to the top.]                          PHYSICAL PROPERTIES
           ADDITIVES: To accelerate the cure, add Part 15X Catalyst. A             Mix Ratio, By Weight or Volume                               1A:1B
           few drops of Part 15X added to one-pound of mixed Parts A and           Hardness, Shore D                                               55
           B speeds the cure significantly. When using Part 15X, exotherm          Pour Time, 1 lb. mix (min)                                       5
           (heat of reaction) increases and can result in shrinkage of the cast    Demold Time (hr) (varies with 15X)                               1
           part. Experiment to determine the right amount of Part 15X to use       Viscosity, 2 min after mix (cP)                              2,480
           but never use more than 1% of the total weight of the mix or the
                                                                                   Specific Volume(in3/lb)                                         35
           final physical properties may be affected.
           If a paste-like consistency is needed for brush-on or trowel appli-
                                                                                                              PACKAGING
           cation, add Poly Fiber or Cab-O-Sil® to thicken the mix.
                                                                                    Unit Weight                             Containers
           PolyColors (see p. 61) can be added LiteCast Part B before mixing
                                                                                        (lb)                       Size              Net Weight (lb)
Casting
Plastics




           with Part A to create plastic of any color.
                                                                                                              A             B            A         B
           CLEAN UP: See p. 47.
                                                                                            3               1 qt          1 qt        1.5          1.5
           SAFETY: See p. 47.                                                              12               1 gal         1 gal       6.0          6.0
                                                                                           60               5 gal         5 gal      30.0         30.0




                                   Poly Plasti-Flex™ Liquid Plastic
           DESCRIPTION: Poly Plasti-Flex™ Liquid Plastic is flexible
           making it ideal for casting decorative trim and molding that needs          FEATURES
           to be mounted on a curved or uneven surface. Plasti-Flex can also           •       FLEXIBLE!
           be used to make special effects castings and props and impact-              •       Wood-like density
           resistant forms, tools and parts. Plasti-Flex has a wood-like densi-        •       Safe and easy to machine,drill or sand (no silica)
           ty and can be drilled, sanded, nailed and screwed.
           MOLD PREPARATION: See p. 46.
                                                                                                      PHYSICAL PROPERTIES
           MIXING AND CURING: See p. 46.                                           Mix Ratio, By Weight or Volume                            35A:100B
           ADDITIVES: PolyColors (see p. 61) can be added Poly Plasti-             Hardness, Shore A                                               90
           Flex Part B before mixing with Part A to create plastic of any color.   Pour Time, 1 lb. mix (min)                                       3
           CLEAN UP & SAFETY: See p. 47.                                           Demold Time (min)                                              ~15
                                                                                   Viscosity, 2 min after mix (cP)                              3,000
                                     PACKAGING                                     Specific Volume(in3/lb)                                         34
             Unit Weight                           Containers
                                                                                                                             Poly Plasti-Flex architec-
                  (lb)                   Size               Net Weight (lb)                                                  tural trim casting. The cast-
                                     A             B            A        B                                                   ing, which is held in a
                  8.1               1 qt          1 gal      2.1          6                                                  curved position, can be
                 38.5               1 gal         5 gal     10.0       28.5                                                  easily mounted on a
                                                                                                                             curved surface.
                192.5               5 gal       5 x 5 gal   50.0      142.5


           Polytek
                             ®


    54
           Development Corp.                                                                                              (610)559-8620 • (800)858-5990
                                                                                      Casting Plastics/Resins                       4
                                                           ®
                                   Polygel Liquid Plastics
                                                       U.S. Patent # 5,128,433
                           ®
DESCRIPTION: Polygel Plastics produce strong, light-weight
mold shells and are ideal for shells built up with a brush or spat-     FEATURES
ula on vertical or overhead surfaces. Sprayable Polygel Shell is        •   Easy -- 1:1 mix by weight or volume
ideal for large surface area applications where brushing may be         •   Fast -- same-day mold shells
impractical. Polygel products consist of liquid Parts A and B, that
                                                                        •   Strong and lightweight
after mixing 1:1 by weight or volume, immediately self-thicken.
                                                                        •   Color-coded mix indication
MIXING & CURING: See p. 46 for general guidelines.
                                                                        •   Long life for molds and shells
For Polygel Plastic-75, mixing of Parts A and B should be rapid
and thorough. Most mixing should be completed within ten sec-
onds or so before gelling begins and while the mix is still liquid                                           This photo shows
to minimize air entrapment. Mix only enough that can be applied                                              Polygel ® Plastic-75 being
during the working time. Polygel Plastic-75 generates heat when                                              applied with a spatula
mixed, so use rubberized cotton gloves to ease handling of the hot                                           over a Polygel 35 rubber
container. Once mixed, dumping the thickened mix on the surface                                              mold to create a rigid
to be coated and quickly spreading into a thin layer will cool the                                           plastic mold shell. Notice
mass and extend working time by a minute or two. Do not try to                                               that the uncured plastic
demold Polygel Plastic-75 until adequate cure time has elapsed as                                            is thixotropic -- it can be
it may be somewhat brittle.                                                                                  moved around the mold




                                                                                                                                           Casting
                                                                                                                                           Plastics
Polygel Shell Plastic is a rapid-setting liquid plastic designed for                                         surface but does not drip
spray applications. Hand mixing is not recommended. When                                                     or sag.
meter-mixed and sprayed 1:1 by volume, Polygel Shell gels sev-
eral seconds after contacting the surface being covered, then
remains in a workable grease-like state for 1 minute. Shells or                                              The photo below shows
castings can be demolded in 2 hours depending upon thickness                                                 the brushed Polygel 35
and ambient temperature. Thicknesses <¼-inch may require                                                     mold supported by its
longer cure time. Thin, tough coatings can be applied to many
                                                                                                             thin, lightweight Polygel
surfaces such as carved foam. Mold shells should be approxi-
                                                                                                             Plastic-75 shell. The hol-
mately ¼-inch thick. When spraying a mold shell, thicknesses
                                                                                                             low, rotocast part was
>½-inch are not recommended as shrinkage can occur upon cur-
                                                                                                             cast using EasyFlo 120
ing and cooling. For additional strength, lay fiberglass strand or
                                                                                                             and swirled PolyColor
mat while applying Polygel Shell. For very large shell sections,
                                                                                                             dye to achieve a marbled
supporting structures such as boards or metal rods can be attached
                                                                                                             appearance.
to prevent warping or damage during use.
STORAGE: In order to maintain dimensions, Poly Plastic mold
shells must be stored in temperatures <100°F. Also, the shells
must not be distorted in storage (e.g., no heavy objects placed on
top). See p .47.
CLEAN UP & SAFETY: See p. 47.

                       PACKAGING
           Mix Ratio 1A:1B (by weight or volume)
                                                 Unit Weight
                                                     (lb)
                                                      4
  Polygel Plastic-75
                                                      16
                                                      80
                                                     900
  Polygel Shell                                       80
                                                     900


                                                                                                                    Polytek
                                                                                                                                       ®


                                                                                                                                           55
www.polytek.com                                                                                                     Development Corp.
           4    Casting Plastics/Resins


                                                        Polypoxy Resins             ®



           DESCRIPTION: Polypoxy® Resins and Poly Cure Hardeners are
           liquids that, after mixing in proper ratio, cure at room temperature                         APPLICATIONS
           to high-strength plastics. Resins can be cured with various cura-
           tives enabling users to select the best system for a particular use.                  Polypoxy ® 1010 + Poly Cure 1212
           The mix ratio for each curing agent and resin blend varies. For                                Bonded bronze
           best results, carefully weigh the components.
           Polypoxy ® 1010 is a clear resin for use with fast Poly Cure 1212                    Polypoxy ® 1010 + Poly Cure 1220
           for small castings such as bonded bronze or with fiberglass or                      Decoupage coatings and glass bonding
           fillers for lay-up and mother molds. Use with Poly Cure 1220 for
                                                                                                Polypoxy ® 1030 + Poly Cure 1212
           decoupage clear coatings, glass bonding and many other uses
                                                                                               Small castings and tooling applications
           where a nearly colorless, clear, low viscosity resin is required.
           Polypoxy ® 1030 is an aluminum- and mineral-filled resin for                          Polypoxy ® 1030 + Poly Cure 1230
           lay-up or small castings when cured with Poly Cure 1212. For                                Larger vacuum molds
           larger vacuum forming molds and other tooling uses, cure with
           Poly Cure 1230. Parts made with Polypoxy 1030 can be machined,
           drilled and burnished with steel wool to a pewter finish.
           SURFACE PREPARATION: Polypoxy Resins are adhesives                                               PACKAGING
           and bond to many surfaces. If adhesion is not desired, surfaces           Product                Unit Weight (lb)     Container
           must be made non-porous with a suitable sealer, such as wax,
                                                                                     Polypoxy 1010                2.0              1 qt
Casting
Plastics




           PVA, lacquer or other coatings. The surfaces must then be coated
                                                                                                                  9.0              1 gal
           with a release agent such as Pol-Ease 2300. Poly 74 Series rubber
                                                                                                                  45               5 gal
           molds require only a light, thorough coating of Pol-Ease 2300 for
           excellent release of epoxy castings. Perform a small test cure.           Polypoxy 1030                3.0              1 qt
                                                                                                                 12.0              1 gal
           MIXING: Polypoxy and Poly Cure must be mixed in the ratios
                                                                                                                  60               5 gal
           shown below. Mix ratios are by weight except for Polypoxy 1010
           and Cure 1220, which can be mixed 1:1 by volume. Polypoxy and             Poly Cure1212               0.25              4 oz
           Cure must be thoroughly mixed and poured as soon as possible                                           2.0              1 qt
           after mixing to ensure low viscosity and good flow. Watch a clock         Poly Cure 1220              0.25              4 oz
           to avoid being caught with unused, cured material.                                                    2.0               1 qt
           HEAT RESISTANT CASTINGS: Polypoxy 1030 offers good                                                    8.0               1 gal
           heat resistance. Call Polytek for more information.                                                    40               6 gal
           CLEAN UP: See p. 47.                                                      Poly Cure 1230              0.25              4 oz
                                                                                                                 2.0               1 qt
           SAFETY: Before use, read product labels and Material Safety
                                                                                                                 8.0               1 gal
           Data Sheets. Follow safety precautions and directions. Poly Cure
                                                                                                                  45               6 gal
           Hardeners cause severe eye and skin burns. Do not get in eyes or
           on skin. WARNING: The epoxy cure reaction is very exothermic
           (see p. 6). Do not cast large masses -- doing so can result in a fire!

                                                                  PHYSICAL PROPERTIES
            Polypoxy + Poly Cure                            1010 + 1212              1010 + 1220           1030 + 1212         1030 + 1230
            Parts Cure per 100 of Polypoxy                            15            85 (1:1 by vol)                   6                  15
            Mixed Viscosity(cP)                                   3,000                      3,000              10,000               5,000
            Pour Time, 150 g mix @ 77°F (min)                          25                        30                  30                 120
            Demold Time @ 77°F (hr)                                  4–8                         48                  24                  24
            Maximum Casting Thickness (in)                            0.5                       1.5                 3.0                 8.0
            Shore D Hardness                                           95                        80                  98                  95
            Specific Gravity                                        1.13                       1.07                1.70                1.70
            Specific Volume (in3/lb)                                24.5                       26.0                16.3                16.3
            Density (lb/in3)                                     0.0408                     0.0386              0.0614              0.0614


           Polytek
                             ®


    56
           Development Corp.                                                                                       (610)559-8620 • (800)858-5990
                                                                                                    Speciality Materials                5
     Speciality Mold Making & Casting Materials
This section describes a few speciality mold making and casting          Latex - Tough, one-part brushable, castable rubbers
materials offered by Polytek. These materials can be used in
                                                                         Wax - Castable, carvable version; skin-safe version accept-
conjunction with Polytek’s traditional mold rubber and casting           able for body molding
plastic products, enabling users to tackle virtually any mold
                                                                         Hydrogel - Safe for skin contact - for body molds & life casting
making and casting challenge.


                                                  Poly Latex 60
DESCRIPTION: Poly Latex 60 is a one-part, brush-on liquid                FEATURES
that, after multiple coats, builds up to form a tough rubber blanket
                                                                         •    Brush-on liquid
mold. Molds made with Poly Latex 60 are often used for casting
plaster, concrete and limited casting with some resins.                  •    Great for casting highly ornamental plaster and concrete
                                                                         •    One part, no mixing or weighing needed
Poly Latex 60 has better tear strength than synthetic rubbers and
                                                                         •    Tougher than any other mold rubber
is sometimes preferred for molds that are peeled off the casting
like a sock. However, two-part, synthetic rubbers like Polygel®         dry completely before applying more latex.
products can be brushed on to final thickness in an afternoon and
                                                                        The latex must be thoroughly dry and heat cured prior to remov-
should be considered as a latex alternative.                            ing from the model. Heating in a warm oven at 110-150°F for 6 to
MODEL PREPARATION: The model should be free of oil,                     8 hours ensures a complete cure. If heat curing is not possible,
grease and dirt. Wood, oil-based clay, stone and glazed ceramics        place the mold in a warm area for a week to help to strengthen the
generally do not require any sealer. Plaster, unglazed ceramics,        rubber.
copper containing metals, water clay and cement should be sealed        Clean up wet latex with soap and water. Dried latex can be soft-
with shellac. Models made of other materials should be patch test-      ened with waterless hand cleaner and washed away.
ed by applying a coat or two of latex to a small area. If the latex
turns dark or sticks after drying, a sealer should be applied.          USING THE MOLD: Avoid exposing the mold to oils, grease or
                                                                        solvents. Molds can be washed with soap and water. Before cast-
Models with sharp edges or points may yield a better mold if the        ing plaster or cement, wet the mold with a 1% solution of deter-
points are dulled slightly by sanding prior to sealing.                 gent in water to aid releasing air bubbles from the mold surface.




                                                                                                                                                Speciality
                                                                                                                                                Materials
Firmly mount the model on a suitable base board (i.e., plywood or       Usually, no other release is necessary. For resin casting, a release
a sink cutout available from kitchen counter shops). Drill a hole       agent such as Pol-Ease® 2300 or PVA is needed. Most resins
through the base board to allow air to escape from within the           shorten the life of a latex mold -- Polygel® or Poly-Sil® rubber
model so that trapped air does not cause defects in the mold.           molds may last longer.
APPLYING & CURING: Brush a thin coat of latex on model                  SAFETY: Before use, read product label and Material Safety
using care not to puddle the latex. A gentle stream of air may help     Data Sheet. WARNING! Poly Latex products contain ammonia
to blow latex into the finest detail and break any bubbles. Each        and causes eye and skin irritation. Avoid skin and eye contact.
coat should dry in 4 to 16 hours if placed in a warm, ventilated
                                                                        Use with adequate ventilation. In case of contact, flush eyes with
room. Drying time depends on temperature and humidity. Warm,
dry air is necessary for fast drying. When dry, the latex loses its     plenty of water for 15 minutes and seek medical attention.
milky appearance, and becomes slightly transparent and amber in         Remove from skin and clothing with soap and water.
color. The next coat should be applied as soon as the first coat is     STORAGE LIFE: At least 3 months in unopened containers
dry. From 6 to 30 coats may be needed depending on the desired          stored at room temperature (50-70°F). Opened containers should
mold thickness. Molds are typically 1/16- to 1/8-inch thick.            be tightly resealed. As latex ages beyond 3 months, it will not cure
For large, flat models, apply latex in a checkerboard pattern, alter-   to as supple a rubber and shrinkage on drying may increase and
nating squares between coats. Since there is some shrinkage on          toughness of the mold will decrease. Exposure to temperatures
drying, the patchwork method reduces stress and warping of the          below 40°F and above 80°F may damage latex, causing irre-
latex as it dries.                                                      versible coagulation. DO NOT ALLOW TO FREEZE.
Latex can be thickened with ground cork, sawdust or Cab-O-Sil®
in order to fill undercuts. Thickeners must be completely wet out                                 PACKAGING
with latex and applied to the outside surface of the mold. The
                                                                               Unit Weight (lb)                   Container
thickened latex must be allowed to dry completely as wet spots
trapped in the latex can cause delamination of the mold.                             2.0                             1 qt
                                                                                     8.0                             1 gal
To reinforce latex molds, imbed muslin, burlap or polyester fabric
                                                                                     40                             5 gal
in the rubber. The fabric should be laid into a wet coat of latex and
                                                                                    400 lb                          55 gal
then saturated with latex throughout. Allow the saturated fabric to

                                                                                                                        Polytek
                                                                                                                                            ®


                                                                                                                                                57
www.polytek.com                                                                                                         Development Corp.
             5    Speciality Materials


                                    Poly Latex False Face Compound
             DESCRIPTION: Poly Latex False Face Compound is a one-part
                                                                                      FEATURES
             pourable liquid that, when poured into a dry, unsealed gypsum
             mold, cures to a high-strength, flexible casting rubber. False Face      •    Easy one-part rubber—no mixing or weighing
             was formulated to produce flexible hollow parts for uses such as         •    Tougher than any other mold rubber
             novelty masks, flexible sculpture and animatronic applications.          •    Good reproduction of fine detail
             MODEL PREPARATION: To cure properly, this product must                   •    Forms hollow castings without roto-molding
             be cast into dry, unsealed, porous plaster molds. The user must
             determine the suitability of other porous mold materials.               tures accelerate drying time.
             MIXING AND CURING: Shake or stir Latex False Face before                Clean up wet latex with soap and water. Dried latex can be soft-
             use. Pour into a prepared gypsum mold. Tilting or lightly vibrat-       ened with waterless hand cleaner and washed away.
             ing the mold may help eliminate bubbles if the mold contains            USING THE CASTING: Lightly dust the inside of the casting
             complex undercuts or deep details. For a thin skin, pour the excess     with talc in order to prevent the dry rubber from sticking to itself.
             latex back into the container immediately. For a thicker skin,          Avoid exposing the casting to oils, greases or solvents. Castings
             allow the latex to stay in the mold longer before pouring off           should be stored out of direct sunlight.
             excess. A standing time of 15 minutes yields a 3/32-inch thickness
             in a dry No. 1 Pottery Plaster mold. Denser plasters are not as         SAFETY & STORAGE: Same as Poly Latex 60 (see p. 57).
             absorbent and thicknesses build slower. Allow False Face to dry
                                                                                                                Latex False Face molds can be made
             in the mold for 24 hours at room temperature. Elevated tempera-
                                                                                                                by dipping a dry, porous plaster model
                                                                                                                into False Face. The longer the model is
                                       PACKAGING
                                                                                                                submerged, the thicker the mold. This
                     Unit Weight                       Container
                                                                                                                technique is only suitable for models
                          2.0                             1 qt                                                  with a shape that won’t trap air when
                          8.0                             1 gal                                                 placed upside down in the False Face
                          40                              5 gal                                                 liquid.



                                                                   Poly Wax 15
Speciality
Materials




             DESCRIPTION: Poly Wax 15 is a white, hard, low shrinkage,               FEATURES
             mineral-filled wax, which can be cast and carved. When cast, it         •    Ideal for prototypes
             replicates the mold surface in detail and finish. Tool cuts are         •    Cast carving blanks from rubber molds of rough originals
             smooth and lustrous. Dull surfaces can be hand polished with a          •    Suitable for master models
             soft cloth to a satin luster.                                           •    Smooth and lustrous surfaces
             MELTING AND CASTING: Poly Wax 15 softens below 130°F
             and is quite fluid at 160°F. Viscosity decreases rapidly as temper-     cantly prolong the procedure. Casting temperatures that are too
             ature is increased. At 200°F, components of the wax separate            low will result in surface bubbles and “knit” marks because the
             slightly. Mix the melted wax thoroughly before pouring.                 wax solidifies too rapidly on the mold surface.
             Complete mixing is quick and easy to determine visually -- mixed        Poly Wax 15 can be poured in Poly 74 Series, Poly-Fast 72-40,
             liquid wax is uniformly colored with no streaks. Use a non-porous,      Poly-Sil®, Polygel® or Hydrogel® molds. Latex will be softened by
             heat resistant stirrer such as a metal spatula. Pour temperatures are   continual pours of Poly Wax 15. Most heat resistant resins and
             typically 210°F-280°F; however, the ideal temperature is depen-         metal molds are also suitable; however, a small trial casting is
             dent on the mold size, shape and material. Poly Wax 15 holds tem-       always recommended to be sure castings release satisfactorily and
             perature for a long time, so large or multiple molds can be filled      do not damage the mold material.
             in a single pour. When slush molding, excessively high tempera-         SAFETY: Before use, read product labels and Material Safety
             tures will cause remelting of layers already laid down and signifi-     Safety Sheets. Hot wax can cause severe burns and ignites easily.
                                                                                     Avoid skin contact. Do not heat with an open flame. Do not heat
                                PHYSICAL PROPERTIES
                                                                                     above 280°F since vapors can ignite.
               Softening point                                          126°F
               Use temperature                                    210 - 280°F        STORAGE LIFE: At least 12 months from date of shipment.
               Viscosity        @ 100°C (212°F)                        116 cP
               Density (in3/lb) @ 25°C (77°F)                            19.5                                  PACKAGING
                                @ 100°C (212°F)                          21.6                      Poly Wax 15 is available in 5-lb blocks

             Polytek
                                ®


      58
             Development Corp.                                                                                          (610)559-8620 • (800)858-5990
                                                                                                    Speciality Materials                5
                                                Poly Skin-Wax
DESCRIPTION: Poly Skin-Wax is a liquid at temperatures as
                                                                         FEATURES
low as 125°F and it is somewhat elastic after solidifying. It can be
applied to models using dip or brush-on techniques. Poly Skin-           •    Safe for skin contact
Wax has been formulated with non-toxic materials and is safe for         •    One-part mold making compound
skin contact provided temperature is carefully controlled.               •    No mixing -- simply melt and use
MODEL PREPARATION: When making a mold of a body part,                    •    Fast -- make a mold in 5 to 10 minutes
coat skin and hair with baby oil before applying Skin-Wax. Molds         •    Easily repaired with a dab of warm wax
can only be made of body parts that are covered with short and           •    Flexible when warm
light hair -- do NOT attempt to make molds from hairy areas. For         •    Self releasing from most surfaces
most other non-porous models, Poly Skin-Wax is self releasing
                                                                         •    Reusable
and, therefore, no release agent is needed. Make a small test mold
on a surface identical to the model to determine that release prop-
erties and hardening of Skin-Wax is suitable.                           the hand. Holes can be sealed later with a dab of molten wax.
PROCEDURE: Use a therapeutic paraffin bath, available from              SAFETY: Before use, read product labels and Material Safety
medical supply stores, to melt Poly Skin-Wax. A crock pot can be        Safety Sheets. Follow safety precautions and directions. Do not
used to melt Skin-Wax; however, extreme caution must be exer-           heat with open flame. Do not heat above 280°F since vapors can
cised to ensure that the wax is not overheated. To melt Poly Skin-      ignite. Use with adequate ventilation. Do not use in the presence
Wax, heat to 160-180°F. Skin-Wax must be cooled to 125-135°F            of sparks or open flame. Exercise extreme caution when applying
before contact with skin! Even this temperature may cause dis-          Poly Skin-Wax to the skin. While Poly Skin-Wax is safe for skin
comfort in some individuals. Do not use Skin-Wax on sensitive           contact, it is not recommended that repeated castings be made
areas such as the face. The wax must be just hot enough to pro-         over a short period as the hot wax tends to remove skin oils and
duce good results; a few degrees hotter can cause considerable dis-     can cause irritation. For skin applications, avoid reusing wax that
comfort. Test judiciously on small areas.                               may have absorbed irritating substances from casting materials.
Stir Skin-Wax often during melting and use since temperature            STORAGE LIFE: At least 12 months from date of shipment.
variations in an unstirred bath can result in solidified wax in one
area of the bath while another area heats enough to cause burns.




                                                                                                                                              Speciality
                                                                                                                                              Materials
Monitor temperature in several places in the bath (i.e., near walls,
center and at several depths). Use an accurate thermometer.
Apply Skin-Wax by dipping the model, brushing on or slowly
pouring over the model surface. For rapid cooling, immerse the
wax-coated model in cool water between coats. Skin-Wax can be
reinforced by laying fabric such as cheese cloth onto the previous
coat and then applying wax to saturate the fabric.
Although some flexibility remains in Poly Skin-Wax at room tem-
perature, if flexibility is needed to remove the model, it is best to
remove it as soon as the wax cools into the elastic (temporarily
deformable) state. For model shapes that do not allow removal
with the mold intact, the mold may be carefully cut and later
rejoined using a warm metal spatula or by “welding” with molten
wax. Small air vents punctured in the mold using a pin or wire                                    The hand is dipped into melted Poly
may help release the mold from the model; for example, in cast-                                   Skin-Wax (125°F) then into cold water to
ing a hand, pinholes at the end of each finger facilitate removal of                              harden the wax. Over the next few min-
                                                                                                  utes the process is repeated 2 or 3
                                                                                                  times to buildup mold thickness. After
                   PHYSICAL PROPERTIES
                                                                                                  the wax is hardened, the mold is slipped
 Softening Temperature                                     125°F                                  off the hand and is ready for casting.
 Use Temperature                                      125-180°F                                   Plaster, cement, rubber or plastic can be
 Viscosity @ 180°F                                       190 cP                                   poured into the hand mold. Be careful
 Specific Volume (in /lb)
                      3
                               @ 77°F                         31        not to use a casting material that generates significant heat upon
                               @ 180°F                        34        cure. The wax is removed from the casting and can be melted
                                                                        for reuse. That casting is detailed -- fingerprints and all!


                                                                                                                        Polytek
                                                                                                                                          ®


                                                                                                                                              59
www.polytek.com                                                                                                         Development Corp.
             5    Speciality Materials

                                                                 ®
                                       Hydrogel N Mold Compound
                                          ®
             DESCRIPTION: Hydrogel N is a dry, white powder that when
                                                                                    FEATURES
             mixed with water at a 3 parts water to 1 part Hydrogel N by weight
             ratio (approximately 1 water to 1¼ Hydrogel N by volume) yields        •   Non-toxic-- Safe for body casts
             a creamy mix with a 5-minute working time. Working time may            •   Easy to use: just add water and mix
             be extended using the optional liquid retarder described below.        •   Good reproduction of fine detail
             Demolding can be done, with care, 2 to 3 minutes after mix can no      •   Early strength for fast demold
             longer be worked.
                                                                                    •   Variable working time
             MODEL PREPARATION: Hydrogel N can be poured on most                    •   Low cost
             surfaces with minimal preparation, but a small test cure should be
             made prior to use to be sure Hydrogel N releases cleanly and does                                                    Hands up and on
             not damage water sensitive surfaces. A thin coat of petroleum jelly                                                  the table! With the
                        ®
             or Pol-Ease 2300 release agent will seal most questionable sur-                                                      use of Hydrogel®N,
             faces adequately.                                                                                                    these children each
             MIXING AND CURING: Weigh or measure proper amounts of                                                                made a plaster cast
             Hydrogel N powder and room temperature water. Mix together                                                           of their own hand at
                                                                                                                                  a Vacation Bible
             rapidly, but avoid whipping in air. A turbo mixer on a variable
                                                                                                                                  School craft ses-
             speed drill is recommended. Thicken with more powder, thin with
                                                                                                                                  sion. Molds for 35
             more water. Apply to surface with a flowing motion, pushing air                                                      hands were made in
             ahead of material. Optional liquid retarder may be premixed with                                                     less than 2 hours!
             water to extend working time.
                                                                                   USING THE MOLD: Plaster or waxes below 212°F may be
             Hydrogel N bonds to itself if the previous mix is not completely
                                                                                   poured in Hydrogel N molds. Castings should be made in freshest
             gelled. Thus, a large mold requiring more than one mix should be
                                                                                   possible molds for best results. Hydrogel N molds will shrink as
             made by mixing a series of mixes within 5 minutes of one another.
                                                                                   they dry. Molds may be kept useable in plastic bags or sealed con-
             Wiping a saturated solution of water and baking soda (sodium
                                                                                   tainers for up to a few days. Molds should then be discarded
             bicarbonate) on gelled Hydrogel N will aid bonding of a fresh mix
             to gelled material. Food color added to the bonding solution aids     SAFETY: Before use, read product label and Material Safety
Speciality




                                                                                   Data Sheet. Follow safety precautions and directions. Handle
Materials




             knowing where it has been applied. As soon as Hydrogel N is firm,
             mix and apply a mother mold of plaster. When plaster shell is set,    Hydrogel N carefully to avoid dust generation. Wear a dust mask.
             remove the Hydrogel N mold and for best dimensional stability,        Avoid eye contact. Hydrogel N is not for human consumption or
             immediately make a positive casting.                                  use against mucous membranes. Keep skin contact as brief as pos-
                                                                                   sible. Prior to placing Hydrogel N on hair, hair should be slicked
             Hydrogel N Retarder can be added to the water before mixing it
                                                                                   down with petroleum jelly or cholesterol hair conditioning cream.
             with Hydrogel in order to slow the cure. The table below shows
             the impact of Retarder addition on cure time. [Note: If Hydrogel      STORAGE LIFE: At least six months in unopened containers
             N Retarder freezes, warm the container under running water and        stored at room temperature (60-90°F).
             shake until a clear liquid results.]
                                                                                                   LIQUID RETARDER (OPTIONAL)
                                                                                                   % Retarder                 Approximate
                                                                                                    in Water                  Working Time
                                                                                                       0                         5 min
                                                                                                       3                         7 min
                                                                                                       6                         8 min
                                                                                                       9                         10 min


                                                                                                                PACKAGING
                                                                                     Product                      Unit Weight             Container
                                                                                               ®
                                                                                     Hydrogel N                     0.5 lb                   1 qt
                                                                                                                     2.5 lb                 1 gal
             Hiram Ball, of Ball Consulting Ltd., demonstrates making a live-
                                                                                                                    12.5 lb                 5 gal
             body mold using Hydrogel® N. The safe-for-skin-contact alginate
             yields excellent mold impressions if wax or plaster is cast right       Retarder Solution              2.0 lb                   1 qt
             after demolding.

             Polytek
                              ®


      60
             Development Corp.                                                                                        (610)559-8620 • (800)858-5990

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:278
posted:5/12/2011
language:English
pages:59
mikesanye mikesanye
About