Korean celadon glazes from the 10th through 16th centuries are studied and compared with Chinese celadon. Mineralogy and composition of the glazes are discussed as they relate to the characteristic greyish green color. Wollastonite and anorthite at the glaze body interface, which provide a rough, white reflective surface on Chinese green glazes, is not found on the Korean celadons. Glaze thickness and inclusion content changed over time, but glaze composition seems to have remained fairly constant. Crazing seems to have been used intentionally as a design element in inlaid celadons. Some differences from Chinese celadons may be explained by the smaller size of Korean kilns, which fostered quicker cooling and inhibited nucleation of anorthite, wollastonite, and cristobalite at the glaze-body interface. Korean celadon glaze technology is interpreted as a conservative tradition which evolved through time to meet popular demand as porcelain replaced green glazes for court use. While similar to southern Chinese technology, the characteristic translucency was attained by different means.