EnvironmentTemperature and relative humidity can affect heritage collections in a number of ways, and the two are closely related. During summer it is common to hear people commenting about the weather saying, “it’s not the temperature so much, it’s the humidity,” meaning that we don’t mind being hot, but high humidity can makes us feel pretty uncomfortable. In a funny way this is true for heritage collections too. Humidity has a more direct influence on the stability and preservation of collections than temperature alone.

Extremes of relative humidity (RH) and heat can adversely affect the condition of objects, particularly those made of organic materials. Many materials, however, will stabilise in a particular climate even if conditions are extreme. Once stabilised to the climate these materials will not necessarily be adversely affected by the constant extreme conditions.

If the climate changes, or objects are moved to a different climate, problems can arise. Changes in relative humidity and heat – particularly rapid changes – are potentially far more damaging to most materials than stable extremes.

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