Pyriform Vase

This deep red glaze is known in the West as “oxblood” or sang de boeuf and in Chinese as lángyáo 郎窑, 郎窯, probably named after Láng Tíngjí (郎廷极, 郎廷極, 1663–1715), governor of Jiangxi province, who ran the imperial kilns in the early 18th century.

Achieving this red color can be elusive and very challenging. Copper oxide (cupric oxide, CuO) in the glaze, when fired in a reducing (low oxygen) kiln atmosphere, changes its molecular composition as the oxygen is sucked out to feed the fire. This leaves behind cuprous oxide (Cu2O) and/or colloidal copper, and these tiny metal particles help to refract the light in the glaze and create the distinctive red. The glaze must be of a certain thickness to turn this color, and because the glaze becomes thinner around the rim as the glaze melts and creeps down the vessel, the rim stays white.