Please note that the recommendations in 1. and 2. below
are partially misleading and reflect outdated thinking.
1. Collections are NOT comfortable when you are
comfortable. Humans are very sensitive to temperature, and they are most
comfortable at around 70 degrees F. Collections are very sensitive to
relative humidity (RH), and many types of collections are best preserved at
stable lower RH. Lower temperatures for collections enhance preservation
significantly. Rule of thumb: for every 10 degrees rise in the
temperature, deterioration rates double. Thus, at 70 degrees,
deterioration is twice as fast as it is at 60, four times as fast as it is
at 50, and eight times as fast as it is at 40 degrees. Check the
preservation calculator (http://www.imagepermanenceinstitute.org/shtml_sub/wwwPresCalc.exe)
from Rochester Institute of Technology (RIT) to see the effects of various
levels.
2. The old saw of 72 degrees F and 50% RH does not
provide enhanced preservation for collections. Much better would be 40
degrees F and 50% RH. The 50% RH is higher than many types of
collection objects would "prefer" (such as paper, metals, textiles), but is
necessary since other types of objects such as furniture would crack or distort
at lower RH, and a low RH in the summer is difficult to achieve. The
critical threshold is the growth of mold/mildew, and RH below 60% (at the object
surface) will prevent this. The recommendation of 72/50 was developed half
a century ago for museums as a compromise for the comfort of both objects (50%
RH) and people (72 degrees). A much better recommendation for smaller
buildings, especially those that are historic, is 40%-60% RH and T as low
as possible. This is why certain objects that are extremely sensitive
to deterioration, such as film, are kept in refrigerators or
freezers.
The thinking that collections are comfortable when
people are has led to inappropriate preservation actions and entrenched
perceptions that are hard to dispel. How many historic houses do you know
of that were heated in the winter even though they were unoccupied in a
misguided effort to preserve the collections? Not heating them (or at
least significantly reducing the temperature) would have increased preservation
manyfold. Of course, these comments are generalities, and each specific
situation must be evaluated for its unique needs in order to determine the best
preservation strategy. But in general, cold is good for collections, even
though it may be bad for people.
Marc Williams
President
American Conservation Consortium, Ltd.
4 Rockville Road
Broad Brook, CT 06016
860-386-6058
Fellow, American Institute for Conservation
(AIC)
----- Original Message -----
Sent: Friday, January 16, 2009 9:09
AM
Subject: [MUSEUM-L] Six Tips to Preserve
Your Election Collections
The following is a text-only press release from the federal
Institute of
Museum and Library Services (IMLS). An HTML version of this
release can
be viewed on the agency's Web site at
http://www.imls.gov/news/2009/011609.shtm
Six
Tips to Preserve Your Election Collections
Follow these simple
preventive steps* to keep your treasures safe and
sound for the next
generation:
1. If you feel comfortable, your treasures will be
comfortable.
When you feel hot or cold, damp or dry, so do your treasures.
You
wouldn't feel comfortable living in the basement or attic and
neither
are they. You feel better when there is good circulation; so do
they.
2. Avoid extremes of temperature and humidity.
Strive to
maintain as moderate and stable a level (72 degrees Fahrenheit
and 50
percent relative humidity) as practically possible. When choosing
where to
display or store objects remember that the conditions of the
interior
walls, room, and closets are more stable than those on the
exterior.