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                                               EXTRA-FINE ACRYLIC
                                               STUDIO ACRYLIC AND
                                               ACRYLIC PRODUCTS

  With their extremely tactile texture,        - When acrylic is used in watercolour        extremely complex physical and physi-
  which reacts to the artist’s tool and        techniques, washes remain stable when        cochemical transformations.
  keeps the mark of the movement, and          a second coat is applied. In addition, the
  their concentrated high-quality pig-         pigments are lightfast and there is no       The film is formed in three stages:
  ments, EXTRA-FINE ACRYLIC and STU-           risk of fading.
  DIO ACRYLIC are pleasant to use and                                                       - In the first stage, the water evaporates
  easy to mix; all the colours in each of      2-DRYING :                                   at a speed which depends entirely on
  the two ranges can be mixed with one         THE PHENOMENON OF COALESCENCE                the temperature, humidity and ventila-
  another.                                                                                  tion.
  Matte or gloss effects can be obtained       Our paints are formulated with resins,
  by mixing the paint with the appro-          resulting from the polymerization in         - In the second stage, known as coales-
  priate medium.                               emulsion of acrylic monomers in              cence, the particles are in contact with
                                               water.                                       one another and interpenetrate.
  1-THE ADVANTAGES OF ACRYLIC                  When the emulsion changes from the
                                               liquid to the solid state, it undergoes a    - In the third (film-forming) stage, the
  Acrylic paint has many advantages:           series of transformations involving          characteristics of the film are defined.

  - Artists who dislike the strong smell of
  oil paint and turpentine will be plea-
  santly surprised by these almost odour-
  less products (which contain very little
  The binder used is synthesized as an
  emulsion in water, using no aliphatic
  or aromatic solvents, which are respon-
  sible for the odour. This means that
  when the paint is still wet, it can be
  washed off the tools with water after

  - It dries quickly and is ideal when a
  painting, even unfinished, has to be
  transported. Successive coats can be
  applied easily with no risk of cracking
  or streaks.

  - Mistakes are easily corrected by cove-
  ring with acrylic gesso and painting over.
After the film-forming stage, the film is   dry state, which may affect colour           APPENDIX
insensitive to water (but sensitive to      intensity after drying. The particle size
the solvents in the resin). The physico -   grading of the resins used for EXTRA-        AGEING OF THE FILM:
chemical properties of the film are         FINE ACRYLIC, STUDIO ACRYLIC and             When a film appears dry, it continues
irreversible under the action of water      their auxiliary products has been selec-     to evolve, forming a three-dimensional
molecules and another coat of colour        ted so as to limit this phenomenon and       network. When the network index (the
can be applied instantly as soon as the     to ensure colour fidelity after the film     number of intermolecular covalent
first is dry.                               is dry. Acrylic colours in general tend to   bonds) is high, the film is hard and
                                            change and become less bright as they        insoluble in certain solvents. This har-
Drying :                                    dry.                                         dening is however moderated by the
EXTRA-FINE ACRYLIC                                                                       simultaneous formation of small mole-
Drying time : 40 minutes                    The action of ultra-violet rays :            cules resulting from the degradation of
+ 10% of RETARDER : 55 minutes              This type of polymer is very lightfast.      macromolecules and acting as a plasti-
(drying time increased by 35%)              Ultraviolet action causes little or no       cizer. This degradation is due to a num-
                                            photo-oxidation or photo-degradation         ber of secondary reactions controlled
                                            of the film (conclusions of a study by       by oxygen, moisture in the air and
STUDIO ACRYLIC                              the CNEP).                                   ultraviolet rays. These reactions gene-
Drying time : 25 minutes                                                                 rate organic substances, such as hydro-
+ 10% of RETARDER : 30 minutes              The film:                                    ketones, diketones, diols, aldehydes and
                                            After the film has coalesced, it is          acids, which cause yellowing phenome-
3-THE PHYSICOCHEMICAL ASPECT                pliable and the canvas can be rolled up      na due to unsaturated ketones (diace-
                                            once it is dry with no risk of cracking.     tyl and dibenzalketone), phenomena of
Acrylic thus has many qualities: very                                                    acidification of the film, resulting, for
quick drying time, water as a thinner,      4-TOXICOLOGICAL ASPECTS                      example, in changes in certain pig-
good adherence to any non-greasy sup-                                                    ments, and hydrolysis phenomena
port, the colour does not dull or change    The resins in acrylic paints contain no      resulting in powdering.
when dry.                                   free monomers such as acrylamide,
In the wet state, acrylic emulsions are     acrylonitrile, ethyl acrylate or n-butyl     During crosslinking, the mesh of the
milky, varying with the fineness of the     acrylate, which can cause contact der-       network shrinks and fluids are expel-
polymer particles in the resin. When        matitis and other skin allergies.            led towards the surface of the film or
the film is dry, this milkiness disap-      The paints are pleasant to use because       towards lower levels. This phenomenon
pears.                                      they contain very little ammonia,            is known as syneresis. The film sweats
The colour of paint formulated with         which irritates the nose and eyes. They      and this plays an important role in sur-
this type of emulsion may vary accor-       are practically odourless.                   face flatness and optical qualities: dull-
ding to the diameter of the particles in                                                 ness or gloss.
the resin. In addition, the light refrac-
tion coefficient of these polymer par-                                                   NB: Further information will be publi-
ticles is different in the wet and in the                                                shed as current studies progress.

THIXOTROPY:                                    UNSATURATION:                                             MILKINESS:
The property of certain very viscous           A double bond on oil molecules allo-                      The whitish colour of a film of acrylic
gels which liquefy when stirred, but           wing the phenomenon of siccativation.                     resin in emulsion before it dries.
become viscous again at rest. In other
words, thixotropic paint may have the
following characteristics:
                                                                                    Reactive functions              Covalent bonds
-its viscosity decreases when stirring
-its viscosity decreases when the dura-
                                                Monomers with 2
tion of stirring increases,
                                                reactive functions
-when it is stirred violently for a long
                                                                      1-Diagram of a straight-chain macromolecule
time, the viscosity approaches a final
-when it is left to rest after stirring, it
returns to its initial state fairly quickly.

Strongly diluted paint, used for the             Monomers with 2

first sketches. The first coats should be       reactive functions

the thinnest.

THINNER:                                         Monomers with 3
What is the difference between a sol-            reactive functions
                                                                      2-Diagram of a three-dimensional network based on two monomers,
vent and a thinner?                                                   one of which has three reactive functions
A solvent dissolves a product, in prin-
ciple in any proportions.
A thinner does not dissolve a product,         CHROMOPHORS:
but can be added to a solution of the lat-     A chemical group responsible for the
ter in significant quantities. For             colour of a molecule in a given
example, water dissolves sugar; it is a        medium.
solvent. Syrup is obtained, to which
alcohol can be added, as a thinner. It         RHEOLOGY
makes the syrup more liquid. Alcohol           The science of the behaviour of fluids
alone would have no effect on the sugar.       subjected to chemical and physical
Chemical transformation of certain oils        APPARENT WETTABILITY:
by fixing oxygen from the air, so that a       The tendency of fillers and pigments in
very strong three-dimensional net-             paint to absorb the binder (oil) and be
work is formed. This phenomenon                coated with it.
takes the form of an increase in the
weight of the film of oil used in paint        OIL ABSORPTION:
as it dries. This reaction is activated by     The quantity (by volume) of binder
temperature and ultraviolet rays.              required to wet 100 g of pigment com-
                                               pletely. Oil absorption depends on the
POLYCONDENSATES:                               diameter (the specific surface area) of
Film-forming substances are polymers           the pigment and filler particles.
consisting of macromolecules. The lat-
ter are produced from chains of small          STREAKINESS:
reactive molecules known as monomer            The result of redilution, caused by the
units. A polycondensate (or polymer)           application of a second coat of paint
is a macromolecule obtained through            containing a thinning solvent of the
condensation of monomer units, by a            first coat.
chemical reaction.