Guan ware is a type of imperial ceramic associated with the Song Dynasty. Guan ware vases were made of smooth stoneware and covered in a crackled white (and sometimes soft blue and green) glaze, with round, bulbous bottoms, graceful stretched necks, and narrow lips. These sophisticated ceramics juxtapose meticulous craftsmanship with the unpredictability of the glazing process, in which the glaze cracks once the vessel is removed from the kiln and begins to cool.