Crazing is the phenomenon that produces a network of fine cracks on the surface of a material. In pottery, crazing occurs through the process of contraction and expansion of the clay body and glaze  at different rates.  Usually considered an accidental  defect, crazing can also be caused intentionally for decorative effect.

Ru ware bowl with celadon glaze and crazing. Northern Song Dynasty. Ca. 1100 CE. Dresden State Art Collections.