A firing refers to the green glaze, drying into the kiln after a high temperature firing products. The second firing, refers to the unglazed green body, the first drying after a prime burn, and then glazing, and then the second firing products. A simple process, reduce heat loss. Secondary firing of its superiority even more:
 
(1) by burning, organic matter is oxidized, crystal water is escaped, carbonate and sulfate decomposition in the glaze before the completion, which is conducive to the elimination of glazed defects.
(2) increase the green body pores, improve the ability to absorb glaze, so that low-hanging glaze possible, to improve the smoothness of the glaze.
(3) to improve the strength of green body, is conducive to the follow-up process, is conducive to automation, reduce the damage.
(4) billet veneer burned, easy to pick and choose unqualified products, improve the finished product pass rate.

Many ancient Chinese porcelain such as Tang San Cai, Yaozhou kiln, Azure glaze is after the second firing. For the first time at a higher temperature of burning (1200 ~ 1500 ℃), glazing and then use the lower temperature glaze burning (950 ~ 1050 ℃). Modern industrial ceramics are often used secondary firing.

It should be noted that the firing process of China's daily-use ceramics, are now mostly used in a muffle firing. The fuel used is mainly coal and heavy oil (about 30% of heavy oil), firing equipment is mainly through the tunnel kiln and down draft kiln, firing system is basically manual control. The national average consumption of 10 million tons of standard coal porcelain in more than 10%, while in foreign countries has been widely used gas fuel, rapid flame burning system. Furnace has been basically achieved than the computer automatically control, thermal efficiency and firing quality is very high. The following table reflects the differences in the main technical and economic indexes between Chinese and foreign ceramic firing processes. Comparison of sintering process of Chinese and foreign ceramics Name firing system kiln level fuel thermal efficiency Kg porcelain heat consumption porcelain box weight ratio automation degree kiln
China at the beginning of a 60-year level of the level of coal and heavy oil 20 ~ 30% 12000kcal about 1: 6 ~ 7 no automatic control means 90%.

Fast burning of foreign flame 80 years advanced level of gas and gas 50 ~ 60% 5000kcal about 1: 2.2 has been achieved 98% automatic control.