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 below are partially misleading and reflect outdated thinking.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
www.conservator.com
Fellow, American Institute for Conservation (AIC)
----- Original Message -----
From: Jeannine Mjoseth
To: [log in to unmask]
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.
=========================================================
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