Guan ware Vase with tubular handles, Southern Song dynasty (1127-1279), Zhejiang province, Hangzhou. Stoneware with Guan glaze. H x W: 10.7 x 7.7 cm. Gift of Charles Lang Freer, Freer Gallery of Art, F1911.347.

The glaze on this small vase, a product of the Jiaotan kiln, shows the dense, dark crackle characteristic of imperially sponsored Guan ware. Crazing occurs accidentally as the fired vessel cools, but the Guan crackle was induced by formulating the glaze to shrink more than the clay body, causing the glaze to fracture. Some Guan wares were made from dark clay that lends its color to the glaze crackle; sometimes, the color of the crackle was also artificially enhanced. The glaze that envelopes Guan ware, applied in several layers, is often thicker than the thin clay body.