To predict how an item might deteriorate, one must know the type of collection, its composition, how it decays and how it is stored or exhibited. No single environment is ideal for all objects. Chemical deterioration includes metal corrosion, increased fading and glass decomposition from high relative humidity levels. Plastics and organic materials have inherent and spontaneous deterioration reactions whose rate is determined by temperature and relative humidity. Increases in either temperature or relative humidity speed the deterioration.
Biological deterioration is damage caused by living organisms such as insects, bacteria and mold.
Relative humidity and temperature levels determine whether these organisms flourish or exist at all. Mechanical deterioration is related to either the amount of water absorbed by organic materials, or thermal expansion in inorganic materials, especially metals. The item changes size and shape, leading to cracking, splitting and warping. Stress or the application of different materials will affect the susceptibility of a piece to mechanical deterioration when the environment fluctuates. Chemical Deterioration Chemical reaction rates increase with higher temperature, increased concentration of reactants and increased pressure.