Risk Management > Relative Humidity


Incorrect relative humidity can be broken down into four subgroups: damp (over 75%), above or below a critical value, above 0%, and fluctuations. Mould growth can occur when the relative humidity is over about 75%, and certain minerals or contaminated metals deteriorate above or below critical relative humidity values. Some chemical deterioration reactions slow as the relative humidity is reduced, and stop when the relative humidity drops to 0%. Relative humidity fluctuations cause swelling or shrinkage of organic components, which can result in fracture, crushing, or delamination of organic components. Although incorrect relative humidity can result in considerable damage to vulnerable artifacts, in most cases it does not lead to complete destruction of artifacts.

Costain, Charlie. Framework for Preservation of Museum Collections, Canadian Heritage, 1994.


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