There are two ways to make a ceramic cup glaze: one is to combine the original soil or rock and use it.
There are two ways to make a ceramic cup glaze: one is to combine the original soil or rock and use it. Another method is to mix earth or rock, melt it with fire, and then cool it abruptly to form glass, called a frit. The glaze made in this way is broken into a fine powder mixed with water to make it a sticky juice for hanging billets. If the paste is not enough to adhere to the billet, you can mix dextrin, glycerin or other sticky organic substances in the paste, such as kelp paste, etc. Some blank body immediately hanging glaze after drying in the open air, but also in advance in 800~900℃ low temperature calcination, that is, the so-called plain burning before hanging glaze.
The former method is called "green hanging glaze", which is used much in China. And foreign porcelain is generally used in the later so-called "plain burning" method. Therefore, the first thing to distinguish a piece of porcelain is whether it is uncooked or uncooked, and we can generally know whether it is made in China or abroad. But this can only be used as a relatively convenient clue, of course, for the general master of ceramics people are familiar with. Some Japanese imitators of ancient Chinese porcelain are deliberately designed to make people think that they are hanging at a glance. If a decision is made based on this alone, it is often easy to be fooled.
When hanging glaze, if the blank is fired, it is usually quickly put into the good glaze juice immediately out, so that the glaze will be sucked on the surface of the blank, and coated with a brush or pen as even. In the case of a tea bowl, it is necessary to quickly put the bowl foot into the glaze and hurry up and down two or three times, which is called "dipping the glaze method". If it is large, it can be hung around with something like ladle to fill the glaze, which is generally called "pouring glaze method" or "slipping glaze method".
Raw hanging glaze, if inside and outside a hanging glaze, it is easy to make the body damaged, so it is necessary to inject glaze inside and rotate, to be dried after the outside of the immersion or slip hanging. Also useful brush and pen to paint hanging, this method is mostly used for glaze, such as the early Ming Dynasty blue and white ware foot often appear brush lines, it can be seen that this method has been used. In addition, although there is a method of "hanging", but mainly used for large or thin objects. For example, the thin porcelain, which seems to be able to see through by the so-called "extruder", has no other glaze hanging method except using this method. This method is: first on the inside of the glaze, dry the outside of the blank body thin, and then spray glaze on the outside. For example, the works of the famous Jiao Tan kiln in the Song Dynasty were thin and thick, and the thickness of the glaze was even one to three times that of the blank. If you look carefully at the pieces of these works, it is obvious that there are two or three layers of hanging glaze, so this kind of porcelain is about the spray hanging method. Another example is the peach blossom red in the Kangxi era, which is different from Lang Kiln red. According to the famous letter of Dantekel who lived in Jingdezhen at that time, it was also made by "spraying glaze method".
When the ceramic billet body of hanging glaze is calcined into the kiln, the water and other volatiles contained in the billet and kiln need to be lost and begin to shrink, while the billet body is heated and produces thermal expansion. At a certain temperature, some components of the billet body begin to melt and form liquid to fill the pores in the billet body and shrink again. The glaze also produces thermal expansion and contraction. When the shrinkage of the glaze is larger than that of the blank, cracks will be produced on the glaze, and when the shrinkage of the glaze is smaller than that of the blank, it is easy to produce "deglaze". Some volatiles do not start to evaporate until the temperature is high. In order to prevent gas from escaping and producing bubbles after the melting of the glaze, the temperature of the kiln should not be increased rapidly before the glaze begins to melt, but should be calcined slowly to wait for the gas to exhaust. In this way, it will be heated up after the gas exhaust until the glaze is completely dissolved. If the temperature rises too fast at this time, it is easy to produce blank bubble or glaze bubble.
