The ceramic glaze celadon ranges in color from grayish-green to jade-green. Variations in the color are the result of the glaze accumulating in lower areas into a thicker layer and appearing as a darker shade of the celadon green. The lighter areas of the glaze represent the thinner layers, which can also allow the white porcelain to show through.
Celadon was developed out of a desire to create a glaze that would resemble the much-desired jade and was perfected during the Song Dynasty (960-1276) in China. The distinctive gray or green celadon glaze coloring resulted from iron oxide's conversion from ferric to ferrous iron during firing. The celadon glaze process later spread to other Asian countries, such as Thailand and Korea.