in the firing of pottery, a kiln firing in which the kiln atmosphere is deprived of oxgyen. When this happens, the fuel source seeks oxygen molecules from any other source, such as the pottery body, slip or glaze in the pottery. This creates interesting effects in the fired pottery. When the pottery body is thus affected, it is usually darker. When the slip or glaze is thus affected, it usually results in a luster, or halo effect.