Craquelure

Craquelure is the fine network of interlocking cracks that develops across the paint and varnish surface of an aged painting, caused by the differential shrinkage and stiffening of ground, paint, and varnish layers as they dry and age over centuries. Its pattern is not random: age craquelure tends to follow the weave of the canvas or the grain of a panel, while drying craquelure (caused by an artist applying a fast-drying layer over a slow-drying one) produces different, often wider fissures. Conservators read craquelure almost like a fingerprint — its density and direction help authenticate a work's age and origin, and it is one of the visual cues that distinguishes a genuine old master from a modern imitation.