This is also the reason why ancestors often used sedimentary soil, red soil, black soil or other fine-grained clay to make pottery.

The actual settlements of Chinese tribes are not all along the Yellow River, and pottery can only be made from local materials, so the clay taken may not be as good as that along the Yellow River. In practice, people have developed the elutriation process of clay, and coarse sand particles in clay can be removed by water elutriation.

For example, in the cultural site of Peiligang, a pottery pool was found.

In the process of elutriation, some coarse particles will be broken due to the infiltration of water. If you stay in the water for a period of time after elutriation, this process will be completely carried out, thus greatly improving the plasticity of clay.

From this experience, people began to realize that the plasticity of clay is related to water and its wetting degree. Proper water content is a necessary condition for plasticity of ceramic clay.

Ancestors master water content mainly by experience. They pinch the mud with their hands, which is not sticky or cracked, and feel that some toughness is appropriate. From the knowledge of modern ceramic technology, plasticity only occurs in a certain optimal water content range.

The essence of aging process is that some solid components in clay become gel filled with crystal water under the action of water, and the existence of gel is the chemical material basis of plasticity.

In a word, identifying and selecting clay, and then improving the plasticity of clay through elutriation and aging are important scientific achievements made by ancestors in Neolithic pottery technology.

Some fusible clays often crack during drying and firing. In order to solve this problem, the ancestors first used the method of mixing leaves, stems and rice husks of plants into soil.

It was soon discovered that the leaves, stems and rice husks of these plants would burn and carbonize in the high-temperature barbecue, and finally a cavity would be formed in the structure of the pottery tire, which would inevitably affect the quality of the pottery.

Therefore, when people fire pottery used as cookware, they often mix a little fine sand into clay, and the amount of fine sand depends on the nature of clay and the variety of pottery to be fired.

According to analysis, most of the Neolithic pottery with sand was mixed with a certain amount of sand particles in clay, thus improving the heat resistance of pottery. This is another scientific and technological achievement of pottery making in Neolithic age.

Select raw materials for pottery making, and process clay into mud for later use. The next pottery-making process is a molding process that embodies dexterity and wisdom.

Small household appliances can be shaped by hand, but larger household appliances are not only difficult to pinch by hand, but also more difficult to make very regular. Therefore, our ancestors invented the construction method of mud strip circle.

The construction method of mud strip circle is to make mud strips, then circle them, layer by layer, and then smooth the inside and outside after bonding. In addition, there is the construction method of mud bar tray, that is, a long mud bar is continuously spiraled upwards and then leveled inside and outside.

There is no essential difference between the two methods. They have been used for a long time, and even today's handmade pottery is still widely used.

In ancient times, blanks may be placed on wooden boards, bamboo mats or woven baskets for easy movement and operation. Later, it was found that it was more convenient to operate as long as the bottom pad could rotate, so the slow wheel was invented.

A slow wheel is a kind of disk that rotates with feet or other power. Pottery clay is made into a ceramic blank on the turntable by the method of pottery clay strip coiling, dried slightly, shaped and slapped on the slow wheel.

With the slow wheel, not only the shape of ceramic body can be much more regular, but also the production speed can be greatly accelerated. The use of slow wheels is a far-reaching achievement in the history of ceramic technology and the originator of pulley cars in later ceramic production.

In order to improve the aesthetics of ceramics, before firing, people often use pebbles or bone tools to polish and rub the surface of ceramics to make it smooth. Doing so, just like the flapping effect, will make the ceramics denser and reduce cracking.

This kind of polished pottery was first seen in Peiligang culture, magnetic mountain culture culture, Yangshao culture and Longshan culture, and this technology was very popular at that time.

Before the appearance of glazed pottery, many pottery wares had decorative patterns on their surfaces, which were both beautiful and reinforced the pottery blank. Different decorative patterns often reflect the characteristics of different cultures, that is to say, decorative patterns are not only the expression of artistic beauty, but also the expression of people's beliefs and spirit.

Another method of surface decoration is to hang a layer of pottery coat on the inside of pottery. The method is to make mud from fine mud and then coat it on the surface of semi-dry pottery.

In fact, the method of applying pottery clothes has become popular in Yangshao culture. Red, brown, black and even white pottery clothes can be obtained by using mud with different textures.

Pottery clothes not only make pottery look bright and beautiful, but also facilitate painting. Most painted pottery has a pottery coat on its surface. It is also this decorative method of pottery clothes that laid the foundation for the invention of glaze later.

The molded and dried ceramic blank must be fired at a certain temperature before it can become pottery. The method and temperature of pottery firing is an important link in pottery making, and the chemical changes in the process of pottery making are completed at this stage.

According to archaeological and anthropological data, the most primitive way to burn pottery is not to use a pottery kiln. Experts from China inspected the pottery-making technology of some ethnic minority settlements in Xishuangbanna, Yunnan Province, and found that there are three ways to burn pottery locally: burning it in the open air on the flat ground; Primary sealing and burning of muddy thin shell; Fired pottery in vertical or horizontal caves.

Heap-burning in the open air on the flat ground means that the pottery blank is first placed on the firewood laid on the ground, lit and dried, and then the firewood base is set up around the pottery blank while it is hot to continue the barbecue.

This process takes about two hours and the highest temperature can reach 900 degrees. After burning, the pottery was picked out and coated with shellac while it was hot.

If you make a jar, apply it all over your body to reduce the leakage of the container. If rice straw or sawdust is used as fuel, rice straw should be added at any time during barbecue to avoid the exposure of pottery blank. This method has the advantages of rapid temperature rise and short sintering time, but it has poor heat preservation, uneven temperature and low thermal efficiency, and it is inevitable to burn the blank from time to time.

One-time sealing and burning of thin mud shell is to lay a layer of firewood on the ground as a kiln bed, put a pre-dried ceramic blank on it, pile firewood around and at the top, and then coat it with a thick layer of mud, so that the firewood is wrapped with a layer of mud skin about 1 cm thick, forming a "thin mud shell kiln". After the ignition, poke holes in the top of the kiln with a stick to smoke.

Compared with open-stack firing, this method of firing ceramics obviously has better thermal insulation. The temperature in the kiln can be adjusted by adjusting the smoke hole at the top of the kiln or even lifting the kiln skin close to the ground. The firing temperature is 800-900 degrees, and the fuel consumption is obviously reduced.

Vertical hole kilns or horizontal hole kilns are mostly simple kilns dug on slopes. The kiln chamber is above, the fire chamber is below, and the middle is connected with the fire hole by a fire passage. The ceramic blank is placed on the kiln grate supported by mud columns. The flame generated by the ignition combustion in the fire chamber enters the kiln chamber through the fire passage and the fire eye, and the ceramic blank is barbecued.

From the above data, we can clearly see the evolution process of ancient pottery firing technology from kiln-free to kiln-fired, which shows that the pottery firing technology at that time was still in the primary stage of chemical pottery making.

The ancients made pottery.