When firing porcelain, high temperature will turn the crystal water or liquid water in the glaze into gas. When the glaze layer is thick, the gas water molecules cannot be released by the glaze film, so as to form bubbles under the glaze. When the glaze layer is thin, bubbles break through the glaze layer film and form many pits on the glaze surface. In the process of ceramic production, glaze bubble is one of the main defects in ceramic production. What is the reason?
(1) Bubbles are caused by the glaze itself: the voids accumulated between the particles in the glaze before firing form bubbles.
(2) Formation of technical factors
The air permeability of the glaze layer after drying is poor, and the gas in the pores of the green body is not easy to be discharged, but at high temperature, the gas in the green body passes through the glaze to produce bubbles. When applying glaze, some gases are sealed in the glaze layer, and bubbles may also be generated, or some additives may be added to the glaze to introduce bubbles. During rapid firing, the gas in the glaze is too late to be discharged, and bubbles are formed in the melted and hardened glaze layer.