Wikipedia
Proto-celadon
Proto-celadon (Chinese: 灰釉陶, also 原始青瓷) was a type of Chinese ceramic which developed during the Shang period and Western Han periods. It is often qualified as "proto-porcelain", and was usually adorned with a light yellowish green glaze.
The body of proto-celadon was made of porcelain, with an iron content below 3%. Firing temperature was around 1200 degrees Celsius. Surface treatment consisted of a lime glaze. The type of objects manufactured in proto-celadon were similar to the objects manufactured in bronze.
During the Shang and Zhou periods, proto-celadon was mainly produced in the areas south of the Yangtze river. Following this period, production greatly improved in quantity and quality.