Destruction of ground, paint and protective layer

 Physico-chemical changes of materials and paintings in the interaction with light and air of the ambient is a process called "natural aging" and is responsible for the less or more rapid deformation of the artifacts.

The change of temperature and humidity cause particularly intense destruction. High molecular organic compounds (such as resins, dried oils, textiles, paper, adhesives, wood components) exposed to oxygen and moisture contained in the air, lead to changes of various elements of the work, as well as of the substances used for restoration, due to their swelling and oxidation. Concerning protective layers based on resins, for example, the effects of the so called Wagner oxidation are observed, while by those containing mainly oil – crackeling or scuring.