Celadon is a term for ceramics denoting both wares glazed in the jade green celadon color, also known as greenware (the term specialists tend to use) and a type of transparent glaze, often with small cracks, that was first used on greenware, but later used on other porcelains. Celadon originated in China, and notable kilns such as the Longquan kiln in Zhejiang province are renowned for their celadon works. Celadon production later spread to other regions in Asia, such as Japan, Koreaand Thailand. Finer pieces are in porcelain, but both the color and the glaze can be produced in earthenware.
For many centuries, celadon wares were the most highly regarded by the Chinese Imperial court, before being replaced in fashion by painted wares, especially the new blue and white porcelain, under the Yuan dynasty. Celadon continued to be produced in China at a lower level, often with a conscious sense of reviving older styles. In Korea the celadons produced under the Goryeo Dynasty (918–1392) are regarded as the classic wares of Korean porcelain.
The celadon colour is classically produced by firing a glaze containing a little iron oxide at a high temperature in a reducing kiln. The materials must be refined, as other chemicals can alter the color completely. Too little iron oxide causes a blue colour, too much olive and finally black; the right amount is between 0.75% and 2.5%.
Greenwares are found in earthernware from the Shang dynasty onwards. Archaeologist Wang Zhongshu states that shards with a celadon ceramic glaze have been recovered from Eastern Han Dynasty (25–220 AD) tomb excavations in Zhejiang; he also states that this type of ceramic became well known during the Three Kingdoms (220–265). According to Richard Dewar, the “true celadon”, which requires a minimum 1,260 °C (2,300 °F) furnace temperature, a preferred range of 1,285 to 1,305 °C (2,345 to 2,381 °F), and reduced firing, originated at beginning of the Northern Song Dynasty (960–1127).The unique grey or green celadon glaze is a result of iron oxide’s transformation from ferric to ferrous iron (Fe2O3 → FeO) during the firing process. Longquan celadon wares, which Nigel Wood (1999) writes were first made during the Northern Song, had bluish, blue-green, and olive green glazes and high silica and alkali contents which resembled later porcelain wares made at Jingdezhen and Dehua rather than stonewares.
Celadon glaze refers to a family of transparent glazes, many with pronounced (and sometimes accentuated) cracks in the glaze produced in a wide variety of colors, generally used on porcelain or stoneware clay bodies. Celadon glazes have such popularity and impact that pieces made with it are often referred to as “celadons.”
The Longquan kiln sites in China were especially well-known internationally. Large quantities of Longquan celadon were exported throughout East Asia, Southeast Asia and the Middle East in 13th-15th century. Large celadon dishes were especially welcomed in Islamic nations.