1. old and cool
The phenomenon of “old” and “cool” is that the kiln temperature and oxidation and reduction atmosphere are not normal when it is fired in the kiln. If the temperature is too high, it will be old, if it is too low, it will be cool, that is, it will not be cooked (raw). The kiln temperature is too high and the glaze surface melts excessively, causing the pattern to flow with the glaze, the facade decoration is sloppy, and the plane decoration is irregular and unclear, and the chromaticity fades, which is sparse and tasteless. If the temperature is too low, the glaze surface is not fully melted, the glaze surface is opaque, and the patterns are not clear, while the denier glaze surface is an orange glaze with roughness, poor brightness, and unevenness.
2. Smoking
The smoking phenomenon is caused by the same reason as the “smoke” in the appearance quality of daily-use ceramic products. It is after the glaze is melted, the reducing atmosphere in the kiln is too heavy, too much coal is added too quickly, the ventilation is poor, the carbon is melted and sealed, and cannot be discharged; and the carbon monoxide is full of the kiln, and the combustion is not complete, resulting in carbon sinking on the glaze surface. . Therefore, part or all of the glaze surface is grayish black or brown, which affects the quality of ceramic products.
3. Spike
The underglaze color “blue and white” and “material thorns” mentioned here are different from the “material spots” that appeared in the Ming Dynasty Xuande underglaze blue and white decorations. It is easy to appear “material thorn”. The main reasons are impure material selection, hard material (high temperature), too much impurities in the material, poor grinding, overlapping material lines, and water separation to the edge of the decoration. Because the impurity particles are not easy to melt, dark brown “material thorns” are formed, which protrude from the glaze surface and touch the thorns, which affects the smoothness of the glaze surface.
4. Stripping glaze
Deglazing is a partial unglazed or cave-like depression on the surface of the product. The main reason is that the blank tire is not clean, and there are sweat spots, greasy, glue, etc. in the blank surface and pattern, which are not compatible with the glaze, resulting in peeling glaze. Another example is that the glaze is applied too quickly, the tire contains too much water, the glaze is not tightly adhered, and the glaze is polished too finely and other reasons will also cause glaze peeling.
5. Faint
The main reason for unclear patterns is that the glaze is not properly matched, such as poor transparency of the glaze itself or too thick glaze, too low firing temperature, cool glaze (not cooked), not transparent enough, etc., resulting in hazy bottom phenomenon. Therefore, the decorative pattern is blurred, so it is called “foggy”.
Post time: Dec-03-2022