A pattern of cracks that developed on the surface of a painting as a result of the natural drying and aging of the whole structure of the painting and influenced by the type of environmental conditions to which the painting has been exposed.

The use of different types of paint media and painting support will result in varying types of craquelure. Tempera paintings, for example, will develop a characteristically delicate craquelure, which in some cases may be so fine as to be nearly invisible to the naked eye. Oil paintings, on the other hand, tend to develop a more prominent network of drying cracks; the pattern will vary according to the type of support used. If significant amounts of resins or other complex materials are mixed with the paint, large, disfiguring drying cracks may develop, imparting a texture to the surface of the painting that resembles reptile skin (hence the term alligator cracks). A particular pattern of impact cracks can develop in a canvas painting as the result of a foreign object striking the surface or the reverse of the painting.

Craquelure is considered a natural and, to some extent, desirable phenomenon. Drying cracks do not necessarily indicate that the paint has loosened from the support. Although the visual prominence of excessive crackle pattern can be minimized with retouching, the presence of most craquelure should simply be accepted.

Source: Looking at Paintings: A Guide to Technical Terms / eds. Tiarna Doherty and Anne T Woollett. (Los Angeles: J. Paul Getty Museum, 2009), pp. 24-25.