TECH TALK
MINNESOTA
HISTORICAL Museum Environments
SOCIETY
GETTING A HANDLE ON THE MUSEUM ENVIRONMENT
by
Beth Doyle, Preservation Outreach Intern, Minnesota Historical Society
with Bob Herskovitz, Chief Conservator, Minnesota Historical Society
Fabrics eaten by moths; photographs faded Because most museum and archival materials are
beyond recognition; ancient pottery turning to dust. hygroscopic, i.e., they absorb moisture from the
These are disasters in museums, libraries and other atmosphere, they expand and contract as the humidity
cultural institutions, and preventing them is part of in the air fluctuates. This dimensional shifting causes
the daily routine for curators and directors. One of stress to the object and can particularly affect already
their tools is the ability to control environmental weakened areas such as cracks in furniture or
conditions, which can effectively slow the deteriorated sewing in a book. Some studies suggest
deterioration rate of historic artifacts and documents, that the fluctuation between high and low temperatures
and allow continued access and use for years to come. and RH can do more damage to materials than an
Regular monitoring of conditions is an essential
MHS photo by Eric Mortenson
component of environmental control.
Environmental monitoring generally includes
three parts: temperature and relative humidity; light
exposure; and biological activity. Equipment for
Figure 1, right. environmental monitoring is available from the
Print-outs of outreach program of the Minnesota Historical
data logger Society’s conservation department: The
charts. One
chart shows the Environmental Test Kit and the Electronic Data
desired, ideal Logger can be borrowed by cultural institutions free
steady lines for of charge. (See pages 5 and 6 for details.) Like proper
temperature handling, storage and display techniques, these tools
and RH in a
space with state will help significantly prolong the life of collection
of the art material.
controls. The
second chart The importance of environmental control
shows how environment that remains fairly stable at a “poor”
temperature It is generally recommended that institutions
and RH maintain a temperature of 65-70 degrees Fahrenheit humidity or temperature set-point. It is most
fluctuate wildly and 35-50 percent relative humidity (RH) to slow the beneficial to minimize the fluctuations of RH,
in a different especially if strict environmental control cannot be
deterioration of a wide variety of objects. The
space which maintained. (See Figure 1, above.)
lacks effective temperature in storage areas should be kept at the
controls. lower end of this recommended range while the upper Exposure to light, too, can cause significant
range will be more practical for areas where people are deterioration. We are all familiar with faded old
using or working with collections. This strict photographs and quilts that have lost their color.
environmental control can be difficult to maintain, so Exposing collections to light, both in its ultraviolet
it is important to know why these guidelines exist. (UV) and visible range, can cause major damage to
Poor environmental conditions can lead to collections, sometimes even if they are exposed for
various kinds of damage to collections. High heat, short periods of time. This damage can take the form
humidity and airborne pollutants accelerate the of fading, yellowing or other shifts in colors, or
chemical deterioration becoming brittle. Sources of light exposure include
of materials. These windows, skylights, fluorescent lights and exhibit
Editor’s note: lighting that is too strong or improperly positioned.
T ECH T ALK is a bimonthly column reactions can cause In addition to UV and visible light, infrared (IR)
offering technical assistance on management, paper to become brittle, light is a threat because IR is heat, and heat
preservation and conservation matters that photographs to fade,
contributes to the deterioration of collections.
affect historical societies and museums of all wooden objects to dry
sizes and interests. Comments and and crack, and textiles to Scientific theory holds that for every 18 degrees
suggestions for future topics are welcome. deteriorate rapidly. Fahrenheit (10 Celsius) increase in temperature, the
rate of chemical reaction (such as fading or becoming
3 INNESOTA HISTORICAL S Interpreter • March 1999
MMinnesota History OCIETY Continued on p. 4
TECH TALK • Museum Environments
MINNESOTA
HISTORICAL
SOCIETY Continued from p. 3
Eliminate over-exposure to light by keeping
brittle) doubles. Awareness and control of heat from blinds and curtains closed in collection areas. Turn off
all sources including exhibit lighting is an important the overhead lights or keep them dimmed in low
aspect of an environmental monitoring program. activity areas, especially storage areas. Light sources
Warm, moist environments are particularly in display cases should be properly sized and
conducive to promoting biological attack. Mold arranged to reduce damage. Guidelines for proper
spores, which are present in light levels are readily available from a variety of
MHS photo by Eric Mortenson
all environments, begin to sources, including the Society’s Conservation
grow in humidity levels Outreach Program.
from 60-70 percent (some Step three is to monitor for insects and other
species have been found to pests. A common and inexpensive technique is to use
begin growth at RH levels as sticky traps or “blunder traps,” which are available
low as 45 percent). from many hardware stores or pest control
Insects also prefer warm, businesses. These traps are usually tent-shaped and
wet spaces. Common among have one surface coated with a sticky glue. When
museums and libraries are pests “blunder” into them they get stuck and cannot
such species as the carpet escape. It is also helpful to collect samples of different
beetle, silverfish, cockroach, insects and pests. This aids in the identification of the
powderpost beetle and clothes moth. Mold, insects insects, which yields their life cycles, breeding habits,
Figure 2, nesting habits, and food sources. With this
above.
and pests such as rodents and birds are capable of
Environmental inflicting a large amount of damage in a short time information in hand, the pests can often be eliminated
Test Kit. The period. Without vigilance, whole collections may be without resorting to extreme “chemical warfare.”
kit includes seriously damaged or even lost to their attack.
instruments for What’s been done
measuring
visible and UV What can you do? A crucial step in controlling the environment is
light, a The first step a curator or director can take to to monitor exhibit, storage and other collection areas.
psychrometer control the environment is to set the parameters for Monitoring the environment does not necessarily
for measuring mean buying expensive equipment, but it does
RH, several
the environmental control system at levels that can be
inexpensive consistently maintained. Economics, existing air require diligence and commitment (qualities that
monitoring tools handling equipment, the needs of the collection and curators and directors already have).
(see figure 3), the building itself are all factors The Kanabec County
and a manual. Historical Society (KCHS) is a
in deciding the set points for
MHS photo by Eric Mortenson
environmental controls. The regular user of the Environmental
goal is to have the temperature Test Kit. Twice a year for
and RH as low as possible, approximately five years, KCHS
while eliminating fluctuations in Registrar Jan Franz has used the
Figure 3, right. the readings. kit to monitor the environment of
Monitoring The second step is to take the building. Although KCHS has
tools that time to look around each area in some monitoring equipment of its
institutions keep
the institution and determine own, Ms. Franz uses the kit to
each time they
borrow the what action can be taken keep track of general conditions
Environmental immediately to eliminate trouble in the facility, to check that the
Test Kit: blue areas. Keep external windows environmental controls are
wool card,
and doors closed and seal any working properly, and to use
humidity
indicator card, cracks in window sills, panes equipment that they do not own.
pH pen, and door frames to prevent “We have to be in the ball park
“sticky” trap, outdoor air from entering the building. Open with our RH and temperature,” she said, “it’s a good
and kit manual.
windows bring unconditioned air into the building, way to check that we are.”
causing stress and additional load on the Franz also explained the benefits of using the
environmental control equipment. Unnecessary light meters in the kit to determine light levels and re-
openings can also allow airborne pollutants, insects direct lighting in the exhibit area. “It’s been a real eye
and rodents to enter the building. Protect collections opener to me that the light can be that harmful.” She
from heat sources such as radiators and vents, either stated that recent meter readings were specifically
by moving material away from these elements, or by helpful in determining the lighting of an exhibit of
deflecting the air-flow away from collection material. large plat maps.
4 Minnesota History Interpreter • March 1999 Continued on p. 5
MINNESOTA HISTORICAL SOCIETY
TECH TALK • Museum Environments
MINNESOTA
HISTORICAL
SOCIETY Continued from p. 4 Testing the environment
Inexpensive instruments can give the rough idea
For the Clay County Historical Society (CCHS), a
of the temperature and humidity that is needed to be
second-time borrower, timing
aware of environmental trends. A variety of
of the test kit couldn’t have
MHS photos by Eric Mortenson
thermometers and hygrometers (for measuring RH)
been better. The test kit was
are available and can range in price from $5 to $150 or
ordered mainly for the use of
more. These can be found at local hardware or
the UV meter, according to
electronics stores, or can be ordered through suppliers
CCHS Archivist Mark Peihl.
of preservation materials. Precision instruments and
New exhibit lighting was
instruments that keep records of the readings (either
being considered, and Mr.
on paper or in electronic form) are more expensive.
Peihl wanted to test the lights.
Humidity indicator cards can be obtained readily
“We tested lamps that were
through commercial library suppliers or photographic
possible candidates for exhibit
preservation supply companies. These inexpensive
areas. We wanted to find out
cards, with small patches of moisture sensitive
if we could filter them and
material, change color from blue to pink when
how effective the filters
exposed to humid conditions. (A list of suppliers is
were,” he said.
available from the Society’s Conservation Outreach
On July 19, 1998, a pipe
Program; see p. 6 for contact information.)
burst, flooding parts of the
Lighting can be easily monitored or measured
archives. “We were in the
using simple-to-use blue wool cards or light meters.
process of changing exhibits
Available at library or preservation supply companies,
and it [the test kit] was here
blue wool cards use specially dyed fabrics that are
when we had the water
sensitive to light, and can indicate whether display
break,” said Peihl. Using
lighting or the room lights are causing damage to your
their own equipment and
collections.
tools from the
Light meters will give a more accurate reading of
environmental kit, he continually monitored the RH
Figure 4, the amount of visible and UV light in a room or
levels in the archives during the recovery effort. A
above. Data display case. However, these instruments can be
professional cleaning company also monitored the
loggers in place expensive, and organizations may not need to own
in a museum environment to ensure the humidity levels were under
one. Fortunately, organizations in Minnesota can
exhibit. The control. (See also articles in the September and
data logger can borrow light meters (see below) to help them with
November 1998 issues of The Interpreter.)
be placed their environmental monitoring and control program.
The staff of the Scott County Historical Society
unobtrusively These tools can give a curator an idea of what
(lower photo) (SCHS) used the electronic data logger that they
conditions in the institution are like at a specific point
or more borrowed to good advantage. They documented the
prominently in time. If consistently recorded, a general pattern of
temperature and humidity in their building and made
(top photo) and the environmental conditions in the building can be
the data available to the engineer and conservator who
labeled to established and used to make improvements.
educate the consulted with them about improving the
public about environmental conditions in their building. This Equipment available for loan
the monitoring information, along with other information gathered For more accurate and recorded monitoring, the
that you are by the consultant, was used to formulate
doing. Data Society’s conservation department has two kits
loggers in recommendations that were incorporated into a available to Minnesota cultural institutions. Both the
public areas successful IMLS grant application. Environmental Test Kit and Electronic Data Logger
should be The grant provided funds to modify the heating are free upon request and contain precision
secured to system to improve humidity control, and also for the
prevent theft monitoring equipment and detailed, easy-to-follow
and the loss of purchase of several data loggers so that they can instructions. (See Figures 2 and 4.)
the instrument monitor conditions precisely without having to
and its data. borrow equipment. Corrine Wegener, SCHS curator Environmental Test Kit
of collections, said that it is “critical to have access to The Environmental Test Kit is available, free, to
loan equipment for institutions lacking the budget to cultural institutions in Minnesota. (See Figure 3.)
buy expensive instruments.” These kits come complete with almost everything
you need to test the environment in your
institution. Each kit includes:
5 INNESOTA HISTORICAL S Interpreter • March 1999
MMinnesota History OCIETY Continued on p. 6
TECH TALK • Museum Environments
MINNESOTA
HISTORICAL
SOCIETY Continued from p. 5 Summary
A good environment can slow deterioration and
• detailed instruction manual and sample forms for prohibit biological attack; proper environmental
recording data; control is a useful tool in the fight against time. The
• two light meters (for visible and UV testing); life of collection materials can be prolonged if
• blue wool card for monitoring light levels; temperature and RH can be maintained in safe ranges.
• battery-operated psychrometer for testing In particular, fluctuations in temperature and RH
humidity levels; should be avoided. Proper lighting is also important in
• RH indicator card for testing humidity levels; protecting collection materials from irreversible
• pH pen for testing acid content of housing damage; control of lighting can yield enormous
materials; benefits for the institution, with a very modest outlay
• sticky trap for monitoring insects and other pests; of resources.
• copy of The Museum Environment (Second ed.), A program for monitoring the environment in
by Gary Thomson. exhibit, storage and other collection areas is an
These instruments can help determine base- important tool for curators or directors in their efforts
line temperature, humidity and light levels. You keep to prolong the life of their collections. Such a
the manual, pH pen, RH indicator monitoring program should include consistent and
• The Environmental Test Kit card, the sticky trap, and the blue diligent recordings, and using proper equipment that
and Data Logger are free wool card, so that even after the is available, for instance, in the test kits to help
upon request. return of the instruments, you can provided through the MHS conservation department.
• Easy-to-use manuals provide continue to monitor your institution’s The kits come with detailed instructions and are easy
step-by-step instructions. environment. Loan period: one week. to use. Contact the conservation department for
• Minnesota Historical Society further information at 651/297-1867 or email at
conservation staff is Electronic Data Logger conservationhelp@mnhs.org.
available to answer any Electronic data loggers monitor
questions you may have. and record temperature and relative
• Your only expense is the humidity. (See Figure 4.) These data
return shipping at the end can be used to identify and trouble
of the loan period. Further Readings
shoot environmental problems, or
• To request a kit or for more Appelbaum, Barbara, A Guide to
verify that your environmental
information, call or e-mail Environmental Protection of Collections, Madison,
controls are working properly. The
the Minnesota Historical Wis.: Sound View Press, 1991. (Available for loan
data logger may be used in one or
Society Conservation from the MHS Conservation Outreach Program.)
more locations depending on your
Outreach Program. Phone: Chicora Foundation, Inc., Managing The
needs and situation.
651/297-1867 or 1-800-657- Museum Environment, Columbia, S.C.: 1994.
Upon return of the data logger,
3773; e-mail: (Also available at
an MHS conservator will download,
conservationhelp@mnhs.org analyze and print your data, and palimpsest.stanford.edu/byorg/chicora/chicenv.html.)
Minnesota Historical Society, Manuals for the
send you a copy of the printout and
Environmental Test Kit and the Electronic Data
a written report about your institution’s
Logger. (Available free from the MHS
environmental conditions. Loan period: three weeks.
Conservation Outreach Program.)
Ogden, Sherelyn (ed.), “Monitoring
Temperature and Relative Humidity,” and
Beth Doyle was an Outreach Intern in the MHS conservation “Temperature, Relative Humidity, Light, and Air
department in 1998. Support for the internship was provided by the Quality: Basic Guidelines for Preservation,” in
Land O’Lakes Foundation. She is currently an intern at the Harvard Preservation of Library and Archival Materials: A
College Library Collections Conservation Laboratory, as part of her Manual, Third edition, revised and expanded.
graduate studies at the University of Texas at Austin. She expects to
Andover, Mass.: Northeast Document
receive a Master of Library and Information Sciences degree in 1999.
Conservation Center, 1999. (Available at
www:nedcc.org)
Bob Herskovitz, Chief Conservator in the MHS conservation
department, has directed the Society’s conservation program since Zycherman, L. A., and J. R. Schrock, Eds., A
1987. Prior to that he was the conservator for the Arizona Historical Guide to Museum Pest Control, Washington, D.C.:
Society, Tucson. He served his conservation internship at the Central FAIC and Association of Systematics Collections,
Research Lab for Objects of Art and Science, Amsterdam, Holland. 1988. (Available for loan from the MHS
Conservation Outreach Program.)
6 Minnesota History Interpreter • March 1999
MINNESOTA HISTORICAL SOCIETY