Five solutions to glaze pinholes and air bubbles in the firing operation of ceramic water cups | Win-Win

January 03, 2023

1. In the stage of oxidative decomposition, it is necessary to ensure enough oxidizing atmosphere, the temperature rise should not be too fast, and the oxidizing temperature should not be too low. Before entering the strong reducing atmosphere, generally make the product around 950°C-1050°C, and properly place it in a strong oxidizing atmosphere. Keep warm for a period of time, in order to completely oxidize and decompose the impurities such as organic matter, carbon, iron sulfide and carbonate in the blank as much as possible before the vitrification of the glaze layer, and fully remove the crystal water.


2. In the final stage of reduction, the heating rate should not be too fast, and the temperature difference should be reduced to promote the glaze to fully melt and spread evenly, but it must be prevented from overheating to cause the glaze surface to boil.


3. The strong reducing atmosphere should not be too thick, and the end should not be too late, so as not to cause too much carbon deposition, and it is also conducive to the early burning of carbon deposition and other substances.


4. The kiln operator should perform low-fire operation according to the type of product and the loading density of the kiln car. The loading density of kiln car cup products is higher than that of plates and bowls, and the oxidation temperature can be appropriately higher, and the oxidation time can be extended appropriately. The oxidation temperature of grouting products can be compared with that of plastic products. The temperature should be about 25°C higher, and the oxidation time of grouting products should be longer than that of plastic products. Longer, so that impurities such as organic matter, carbon, iron sulfide and carbonate in the product (products of each part of the kiln car) can be completely oxidized and decomposed as much as possible, and the water of crystallization can be fully eliminated.


5. When the green body is fired in a reducing atmosphere, the atmosphere transition temperature is different due to the formula of the glaze, so it should be carefully selected. Generally, the atmosphere transition temperature should be set at about 150°C before the initial melting temperature of the glaze layer. The atmosphere transition temperature is too low or Too early, because the organic matter, carbon, iron sulfide and carbonate are not completely oxidized and decomposed, it is easy to cause glaze pinholes or bubbles on the product, and defects such as smoke, etc., and the atmosphere conversion temperature is too high or too late, it is easy to use The product produces defects such as cloudy yellow. The temperature at which the strong reducing atmosphere turns into a weak reducing atmosphere should also be properly selected according to the glaze formula. Generally, daily-use porcelain products are turned into a weak reducing atmosphere at around 1250 ° C. If the conversion is too early, the product will easily produce cloudy yellow. If the conversion is too late, it will increase the free carbon absorbed by the blank glaze, which may cause glaze pinholes or bubbles in the product.

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