Generally speaking, there are three kinds, namely oxidation flame, reducing flame flame and neutral flame. When burning kiln, the flame has different properties in different periods. The nature of flame can be roughly divided into three types: oxidation flame, reducing flame flame and neutral flame, and different types of flame have different functions.

1, oxidation flame: refers to the flame in which the fuel is completely burned. When the flame burns completely, a large amount of air must be supplied. At this time, there is enough oxygen and less CO in the kiln. In order to make the water and all organic matter in the green body evaporate and volatilize, and make the green body shrink normally, there must be an oxidation flame stage in the firing process of the kiln.

2. Reduction flame: Reduction flame is an incomplete combustion flame. At this time, more carbon monoxide and hydrogen are produced in the kiln, and no or little free oxygen is produced. Reducing flame can fully reduce the high-valent iron (Fe2O3) in the green body to ferrous oxide (FeO) and turn it into cyan, thus eliminating the yellowing of porcelain. Therefore, reducing flame is often used in the kiln firing process of daily-use porcelain. 3. The neutral flame is between the two.