The wife's surface is generally glazed, the glaze layer is obviously thicker than the original porcelain, with strong gloss, firm and close combination of moss and glaze, and the glaze color is elegant and clear. Porcelain in the Eastern Han Dynasty was obtained under the conditions of raw material crushing, mold-making tool reform, glaze making method improvement, kiln furniture structure improvement and firing technology improvement, which laid the foundation for the development of porcelain industry in the Three Kingdoms, Jin, Southern and Northern Dynasties.
Sintering technology:
Choosing raw materials for porcelain making, mastering the chemical composition of raw materials, fine processing and glazing of raw materials are the internal causes of porcelain making. But when the firing temperature is below 1200℃, porcelain, such as modern fine pottery, cannot be fired. When making celadon, it is necessary to master the reducing atmosphere properly in order to burn it into turquoise glaze. By the Eastern Han Dynasty, Shangyu Kiln had solved the problem of selecting raw materials, and the appearance of Dragon Kiln created conditions for raising firing temperature. Therefore, mature celadon was found in some primitive celadon kiln sites. For example, at the Daheao kiln site in Lianjiang, Shangyu, there are primitive celadon and celadon fragments piled up and burned together in the same kiln. In the ruins of Xiaoxiantan porcelain kiln in Shipu near Dahao, the author selected three pieces of porcelain to measure the water absorption. The thickness of glaze layer is more than 0.2 mm, and the glaze color is light blue without cracks. The tire adopts porcelain stone with iron content below 2%; The firing temperature is above 1250℃, and it has good porcelain, white and fine tire, slightly translucent tire sheet and firm combination of tire glaze. The water absorption is 0.5%, 0.26% and 0. 16% respectively, which basically meets the requirements of modern porcelain.
Since the Eastern Han Dynasty, the firing temperature of some kiln sites has reached about 1300℃, and the firing atmosphere has been well controlled. After entering the Three Kingdoms, the firing technique became more skilled. The firing temperature of Zhang Zishan West Jin celadon tablets in Shangyu is 1280℃, and the firing temperature of Shanxi West Jin celadon tablets in Shangyu is as high as 1300℃, and the firing atmosphere is also high.
The control of sintering atmosphere is mainly to control the increase or decrease of air quantity entering the kiln. The flame properties of celadon during firing depend on the reduction rate of fetal glaze. The greater the reduction ratio, the stronger the reducing ability of the atmosphere; On the contrary, the weaker the reducing ability, when the reduction ratio in the glaze is lower than 0.3, the atmospheric properties gradually change from reduction to oxidation, and when it is lower than 0.2, it becomes strong oxidation.
According to the analysis of Institute of Silicate, Chinese Academy of Sciences, the content of FeO was 0.35%, the content of Fe2O3 was 1.28%, and the reduction ratio was 0.27, so it was fired in an oxidizing atmosphere. The content of FeO in the embryo of Shangyu Yueyao porcelain in the Eastern Han Dynasty is 1.26, and the content of Fe2O3 is 0.30%. Its reduction ratio is 4.2, which is 15 times higher than that of Yin glazed pottery, which proves that the firing atmosphere has been successfully controlled.