Generally speaking, the porcelain clay we refer to refers to the soil obtained by crushing porcelain stones, or artificially prepared raw materials for making porcelain.
This kind of porcelain clay is composed of kaolin, quartz, feldspar, etc., and its main components are silica and alumina.
Among them, kaolin is a kind of clay with kaolinite as the main component.
Because of its poor plasticity and high melting point, porcelain cannot be made from kaolin alone and must be mixed with other raw materials.
It is because of the inclusion of porcelain stone that the porcelain can be fired harder.
Therefore, the textures of low-temperature glazed porcelain and high-temperature glazed porcelain are different. High-temperature glazed porcelain is harder, so the sound of ceramic knocking is also different.
The sound of porcelain with high temperature glaze is crisper, while the sound of porcelain with low temperature glaze is relatively dull.
And all this is caused by the different textures of the ceramics themselves. The hardness of high-temperature glaze porcelain is stronger than that of low-temperature glaze porcelain, while low-temperature glaze porcelain is more fragile.
All these differences can actually be seen from the development history of ceramics.
When the early primitive ancestors made pottery, they just mixed the readily available loess into mud, and then fired simple pottery.
Later, with the development of production and living practices, the ancestors learned to use soil materials selectively.
The washed soil is used to make fine clay pottery, such as plates, bowls and other tableware.
Sand-filled pottery, such as pots and other large containers, is made from soil mixed with gravel.
By the Shang and Zhou dynasties, as potters' understanding of various earth materials deepened.
At this time, people discovered that pottery fired from kaolin has a tight texture, a hard body, low water absorption, and greatly enhanced practicality.
Later, people accidentally discovered that after the pottery made of kaolin was fired in the kiln, there were some shiny things on the wall.
After repeated observation, these shiny things were formed from the dust of the grass and wood fuel used in the kiln falling on the pottery.
Therefore, people mixed plant ash and water into a slurry and painted it on the surface of the pottery.
After firing, the surface of the pottery has a layer of bright glass, which is called "glaze".
Kaolin glaze is fired at high temperature, which is the earliest "porcelain" in China.
Therefore, Chinese porcelain was born.
In terms of time, it is no later than the Shang and Zhou dynasties.
Because there is still a gap in quality between the "porcelain" at this time and the real porcelain later, academic circles call it "primitive porcelain".
Primitive porcelain was developed from pottery. Because it is very different from pottery in terms of quality and function, it was favored as soon as it came out.
There are two main differences between primitive porcelain and pottery. The first is the difference in materials.
Primitive porcelain used kaolin (porcelain clay), which is much more malleable than the clay used in ordinary pottery.
Therefore, it can create more and more practical shapes.
Just like white flour and cornmeal, white flour can be used to make pastries in various shapes such as birds, piglets, puppies, etc.
The shapes that can be made with cornmeal are much less, because its own "gluten" (plasticity) is not as good as that of flour.
Furthermore, the texture is different. Kaolin clay contains higher silica and alumina content than ordinary clay, so the high temperature resistance of its embryonic body is also higher than that of the latter.
The higher sintering temperature makes it hard in texture, compact in matrix, low in water absorption, and more practical.
It can be said that our country is the earliest country in the world to use kaolin.
After the Song Dynasty, people used this white sandy white clay, which is mainly composed of quartz, clay minerals and mica minerals, to precipitate white mud after washing, and used it as a fine material for making porcelain.
The extensive use of this kind of white clay has brought the quality and craftsmanship of porcelain in Jingzhen in the past dynasties to unprecedented heights, surpassing the ceramics of some ancient kilns in northern my country, and its exquisiteness is comparable to that of jade.
When Jingzhen was established during the Jingde period of the Northern Song Dynasty, that is, from 1004 to 1007 AD, the porcelain produced there was already famous throughout the country.
Jing porcelain enjoys a high reputation. In addition to the high level of craftsmanship at that time, another reason is that the mineral raw materials for firing porcelain here are of better quality.
According to research by modern scholars, Jingzhen initially used nearby porcelain stones as raw materials.
By the Northern Song Dynasty, the formula for firing porcelain had been improved, including kaolin clay obtained from local materials.
According to the "JDZ Ceramics Record", the raw materials for firing porcelain in Jingzhen were porcelain stones from Qimen, Hui Province, and white clay from nearby Jingzhen.
In the Yuan Dynasty, the Jingzhen area began to mix a certain amount of kaolin into the blanks.
The quality of porcelain is greatly improved by firing porcelain using a binary formula of kaolinite and porcelain stone.
It is also because of this formula that exquisite porcelain is created that is "as white as jade, as bright as a mirror, as thin as paper, and as loud as sound", making Jing porcelain famous at home and abroad.
Therefore, it can also be seen from this that during the Yuan Dynasty, Jingzhen specifically mentioned that the kaolin found there should be Macang soil.
The Macang clay here is definitely different from the kaolin clay, but the difference is not that big.
Perhaps the difference lies in the ancient people's craftsmanship in processing this kind of clay.
The Macang clay produced by the same process is different from kaolin clay.
It is on the basis of this binary formula of macang soil and porcelain stone, combined with the suma liqing material, that the Yuan blue and white we see now can be formed under the unique porcelain making technology of Yuan Dynasty craftsmen.
Kaolin itself has great advantages. After the discovery of Macang clay with unique characteristics, the so-called binary formula was formed.
It was with all these technologies that Jingzhen became a kiln exclusively for the palace, and after that, the recipe was kept strictly confidential.
With this formula, Jingzhen's porcelain making technology also developed rapidly, and folk porcelain making was left far behind.
In the eyes of Westerners, this method of burning stones into white objects seems to be something only gods can do. They have spent hundreds of years and still cannot explore its secrets.
Later, animal bones were used to make so-called bone china, and finally white glazed porcelain was made.
In modern times, domestic technology was plagiarized by foreign countries, and gradually large foreign companies began to fire normal porcelain. At that time, they truly mastered the craft of porcelain firing.
Through the development process of porcelain, we can see that the utilization of kaolin must have played an important role.
Before the discovery of kaolin, ceramics were only fired with porcelain stone, and the success rate was very low.
The use of kaolin not only expands the source of raw materials for making porcelain, but also changes the performance of porcelain.
From the original single porcelain stone mud material, it has become a "binary formula" of porcelain stone and kaolin.
Porcelain has since been upgraded from soft porcelain with low fire temperature to hard porcelain with high fire temperature.
This is not only an epoch-making event in the history of my country's ceramics, but also brought a series of major changes to the Jingzhen porcelain industry.
Due to its excellent properties, kaolin can be introduced into porcelain bodies, which has brought about major changes in the raw materials and technology of porcelain making in Jingzhen.
In the three historical periods of Yuan, Ming and Qing Dynasty, it achieved great development and reached a leading position in the world. Jingzhen also became a world-famous porcelain capital.