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Wester Archivists-humidity question



In response to Nancy Freeman's inquiry about relative humidity.  I did most of my conservation/preservation training in the Northeast and then returned to the West.  I feel that a lot of the guidelines are written without the climate of the Western US and other dry climates in mind.  I have found that here in ALbuquerque the RH can be between 20% to 35% in the winter, sometimes dipping down to treacherous lows such as 12%!  In the summer "mansoon" season the RH can be between 40% and 55% sometimes reaching above 60%.  I would discourage the use of local dehumidifiers and humidifiers as they are very labor intensive to keep running and introduce the risk of fungal growth.  The best guideline I have found on this subject in from Barbara Applebaum's book entitled "Guide to Environmental Protection of Collections"  Madison, CT:  Sound VIew Press, 1991.  p. 35
"A steady RH every day and night of the year at any feasible level between about 40 and 60% would be virtually ideal for most collections.  For reasons we shall see later, this may be prohibitively expensive and difficult to manage.  A reasonable alternative that would provide significant protections would be to provide a steady RH of about 35-40% in the winter, a steady 60% in the summer and to reaise and lower the levels between the two in the fall and spring, with daily fluctuations of no more than a few percent, monthly levels that change no more tha 5% per month."
You must read more of this section to fully understand the context of this statement.  You may consider hiring an environmental consultant such as Ms. Applebaum or William Lull.
 
Jo Anne Martinez-Kilgore
Cariño Conservation of Books and Paper
1608 Los Arboles Ave. N.W.
Albuquerque, New Mexico  87107
(505) 343-9172