As the internal components of cultural heritage objects interact with the environment around them, chemical reactions occur that result in deterioration. The two main chemical reactions that cause deterioration are hydrolysis and oxidation. These chemical processes affect different compounds in different ways, but generally break down chains of polymers, resulting in loss of strength of the material components.
External factors can significantly speed up the rate of chemical reactions that cause deterioration. The primary risks to collections are elevated temperature, humidity extremes, light, and air pollutants, each of which will be explored in more detail to the right.
While repositories of cultural heritage materials can do little to control the internal components of objects, they can control the key external factors that will extend the usable life of collections.