Kaolin (porcelain clay) has a high iron content, and celadon can only be fired at a high temperature of 1300℃. After control, the iron content in porcelain clay can be reduced and the interference of iron coloring can be overcome, that is, white porcelain can be fired. China started firing white porcelain from the Northern Qi Dynasty, but the white porcelain fired at that time was generally blue, indicating that the iron content was high, the firing temperature was low and the firing process was not mature enough. The tire and glaze of this Sui dynasty white porcelain have completely disappeared from the white and blue phenomenon. There is a white glazed belly pot with dragon handle in Tianjin Art Museum, which is almost the same in shape as this double dragon handle. The inscription at the bottom says "This bottle has a combination", so people call it "bottle". During the Three Kingdoms, the Jin Dynasty and the Southern and Northern Dynasties, due to the great development of porcelain-making industry, porcelain-making technology made great progress, which was embodied in the selection of fetal glaze and the improvement of formula, which promoted the appearance of white glazed porcelain in the late Northern Dynasty. A number of white porcelain bowls, cups and long-necked bottles unearthed from Fan Cui's tomb in Liangzhou in the sixth year of Wuping in the Northern Qi Dynasty in Anyang, Henan Province (AD 575) can be taken as representatives. The embryo and glaze color of these porcelains are milky white, but they are slightly blue in some glaze layers, and there are still traces of celadon, which is the characteristic of early white glazed porcelains. After the Sui and Tang Dynasties, the firing technology of white porcelain was further improved, the color tone was more stable, and the shape of porcelain was more exquisite and beautiful, which became a daily utensil loved by the upper class.