Description of the Twenty
Illustrations of the Manufacture of Porcelain
By Tang Ying, Director of the Imperial Factory at Jingdechen,
in obedience to an Imperial edict... (1743)
3. Burning the Ashes and Preparing the Glaze
"All kinds of porcelain require glaze, and the composition used for glazing can not be prepared without ashes. The ashes for the glaze come from Lo-p'ing-hsien, which is one hundred and forty li to the south of Jingdezhen.
They are made by burning a gray-colored limestone with ferns piled in alternate layers. The residue - after it has been washed thoroughly with water - forms the ashes for the glaze.
The finest kind of petuntse made into a paste with water is added to the liquid glaze ashes, and mixed to form a kind of purée, the proportions being varied according to the class of porcelain.
Within the large jar, in which the mixture is made is placed a little iron pot, through the two handles of which a curved stick is passed, to make a ladle for measuring the ingredients. This is called a p'en. For example, ten measures of petuntse paste and one measure of ashes form the glaze for the highest class of porcelain. Seven or eight ladles of paste and two or three ladies of ashes form the glaze for the middle class. If the paste and ashes are mixed in equal proportions, or if the ashes are more than the paste, the glaze is only fit for coarse ware.
In the picture the little iron pot which is seen floating inside the large jar is the p'en or, measure."
This page is based on an original translation from Chinese by S.W. Bushell, 1899, of a text written on Imperial command in 1743 by Tang Ying, the celebrated superintendent of the porcelain manufacture in the province of Jiangxi. It is widely reprinted. The version most likely to be authentic is the version found in the official annals of the province of Jianxi, Book XCIII, folio 19-23. The first draft seems to have been written in 1735. The version above was added to a set of 'twenty illustrations of the manufacture of porcelain' in 1743. The actual illustrations have never been identified. The text as it appears here is illustrated with photos taken on location by Jan-Erik Nilsson in 1991 and 1992.