In the ceramic decorative glaze, there is also a special glaze called crack glaze. The glazed surface is covered with many small cracks. The lines are thick and dense, thick and thin, long and short, curved and straight, like cracks, like crab claws, like brocade, like water lines. These various lines are in porcelain. The surface forms a decorative taste.
The generation of cracked glaze, like the kiln glaze, was also accidental. Moreover, the glazed crack is a defect in the firing, but when the glazed crack of some products is very special, the texture is uniform and clear, and the surface is covered, giving a special beauty, so people get from it. Inspired to sum up the experience and consciously create cracks in this sleeve, which gradually created a crack glaze.
In the history of China's domestic porcelain, the crack glaze first appeared in the Ge Kiln of the Song Dynasty. [1] It is said that at the Longquan place in the southwestern part of the Yangtze River, there were two brothers and kiln of the family brothers, and the kiln made by the brother was called the kiln, and the kiln made by the younger brother was called the kiln. "Zhouzhou Fuzhi" has the following records: "Zhang Sheng Er, I don't know when, people taste the main kiln, the ware of the second kiln, extremely green, pure, such as jade. But a bottle A glimpse of ten gold." The kiln of his brother, who lives in the main house of the family, is all white and broken, and the number is broken. "Putian" is in Damei Village, Longquan. This is a famous crack glaze produced by Ge Kiln. "Ge Gu Yao" said: "The kiln pattern takes ice cracks and blood." For the plum blossoms, the ink is second. Fine lines, under the lines. "Di Yao" is different. According to "Tao Shuo" and "Tao Lu" and other books, there is no pattern in the kiln. This is the most different place from the "Gao Kiln". The products of the kiln are mostly purple mouth iron. Dress up for the blue, no grain is expensive. From here we can know that the characteristics of the company's products are that there are shards, that is, cracked glaze. The lines are staggered, forming a lot of fine-eyed people, called "caviar lines", the lines are dense, more fine, called "hundred pieces of garbage." As for its glaze color, it is diverse, there are talk about fried rice, Wang Huang, talk, crab shell, tea, dark green and so on.
The reason for the crack glaze is simply that the expansion coefficient of the glaze is larger than the expansion coefficient of the blaze. During the heating process, the glaze surface generates a large tensile stress, and thus the glaze surface forms many cracks. Practice has proved that increasing the content of potassium oxide (K zO) and sodium oxide (Na70) in the glaze, that is, increasing the content of feldspar, or reducing the content of silicon monoxide (5iO z) in the glaze, or diboron (B 20 a) Instead of part of the silica, the expansion coefficient of the glaze can be increased. Of course, there is no limitless increase, otherwise the melting point of the glaze is lowered and it becomes a fusible flowing glaze.
Crack glazes can generally be divided into two major types, one is the filling type than the other type. The filling crack glaze is filled with soot, drawing ink, and the like in the crack of the fired glaze, so that the grain is black and more vivid. It is also possible to fill the texture with the thickness of the colored glaze layer such as copper sulfate, iron sulfate, manganese sulfate, or nitric acid drill, and the conditions of the firing, which affect the image of the crack.
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