How did the temperature of the ancient porcelain kiln reach thousands of degrees?

In ancient times it was mixed with high-quality coal, coal particles and pulverized coal, by a blower.

Oxygen is supplied from the bottom up and pulverized coal is lifted to the point where the temperature is 1,000 degrees Celsius in an instant. Don't wonder how pulverized coal can have such a high temperature. The rotary kiln of our factory has been sprayed into the kiln with a blower so far, and the kiln temperature of the combustion belt is 1150-1200 degrees, which is used to calcine bauxite.

The limit temperature is 1650 degrees, which can melt aluminum ore, sinter ore powder, and burn kiln bricks. Today's ceramic factories can use coal, gas, natural gas or electricity, all of which can reach thousands of degrees. There is also a commonly used method, in the kiln near the observation mouth to put a number of porcelain clay pinched cones, pointed round bottom, there is a hole in the middle, called fire.

This thing turns red and soft when it is hot. Draw a head out with an iron rod at intervals to see how soft it has softened to determine the temperature.

As far as I know, the earliest use of coal to burn porcelain in China was in Tangshan, it seems that it began in the sixties of the last century, and then the coal kiln technology spread to other porcelain-producing areas. Taking Jingdezhen as an example, from the 60s to 1982 was the era of coexistence of coal kilns and firewood kilns, coal kilns mainly burned daily-use porcelain, and firewood kilns burned antique and art porcelain. In 82 the last firewood kiln was abandoned, and then the next ten years were all coal kilns to burn porcelain.

Natural gas kilns appeared in 1992 and soon replaced coal kilns in full. Several other porcelain producing areas, such as Longquan, Dehua and Zibo, have more than ten years of coal kiln period, and now they all use gas kilns. Of course, there may be exceptions, but the gas kiln is undoubtedly the mainstream of porcelain burning in the world.

The advantages of gas kilns over coal kilns and firewood kilns are obvious, and there are three points: first, there is no dust and cinder pollution, no need to cut down trees, and environmental protection. Second, the area is small, and the smallest gas kiln is only two meters square.

Third, the most important thing is that it is easy to control the temperature, just turn the valve when you raise the temperature and cool down. Now there are also many electric kilns, and several large bone china factories in Shandong and Jiangsu use electric kilns. However, the electric kiln has high energy consumption and cannot burn blue and white porcelain.

As for how to increase the temperature to more than 1,000 degrees, it is very simple, control the heat loss. As long as the rate of heating up of the porcelain kiln is greater than the speed of heat dissipation, it will soon reach 1,000 degrees. Today's porcelain kilns have a thick layer of asbestos insulation, about half a meter thick, and there is very little heat loss.

There are many types of ancient porcelain kilns, divided into two kinds of dragon kilns and oval kilns, and can be subdivided into ladder kilns, gourd kilns, Nanfeng stoves, steamed bread kilns, etc., all of which burn wood. The way to reduce heat loss is, first, to build a kiln with thick bricks; Second, except for the flue, it is completely sealed, and the back door of the full kiln is also sealed with bricks, leaving only a small firewood and observation hole.

Due to the different industries, the ceramic firing temperature classification category is not the same

The ceramic industry is generally divided into architectural ceramics and daily ceramics, craft ceramics and special ceramics, and their respective high, medium and low firing temperatures are classified as:

The general division of architectural ceramics: low-temperature ceramics (below 700), medium-temperature ceramics (700--1200), high-temperature ceramics (above 1200);

The general division methods of daily ceramics and craft ceramics are: low-temperature ceramics (below 1200), medium-temperature ceramics (about 1250), and high-temperature ceramics (above 1300); ‘

Special ceramics are more difficult to say, there are very low firing temperatures, and there are also special ceramics suitable for high-tech applications with a firing temperature of more than 1800 degrees.

Then there is the process of ceramic firing is divided into overglaze and underglaze firing process, and the firing temperature is also different, and naturally the firing temperature is different. Glaze porcelain is a porcelain handicraft built on the porcelain that has been made into porcelain, in which the appliqué porcelain is divided into high-temperature ceramics (about 1300), medium-temperature ceramics (about 1200), and low-temperature ceramics (700-800) firing.

The classification of overglaze hand-painted porcelain is relatively simple, generally 700-800 firing; Very little high-temperature resistant overglaze hand-painted porcelain.

The ceramic industry is generally divided into several categories of architectural ceramics and daily ceramics, craft ceramics and special ceramics, and their respective high, medium and low firing temperatures are classified as: 1300: high-temperature glaze, ancient imperial kiln, underglaze color, glaze red and other colors, are high-temperature glaze.

Jingdezhen unique firing high-temperature ceramics, firing temperature of more than 1300 degrees. 1200: medium temperature glaze, 1000 common techniques of ancient folk kilns

Low-temperature glaze, daily tableware is often fired at low temperature, which is inexpensive and easy to mass-produce. 950: Glaze color, often used in the glaze blue and white gold inlay secondary sintering special technique.

900: Embossed gold, in 1300 high temperature glaze, with a thousand feet of gold water applied to the embossed gold technique, the international standard content of 12%-18%, not easy to oxidize, as good as new. Below 800:

It is called pigment, and the surface of the vessel is like porcelain and non-porcelain, and the glaze is not glazed, which is called pigment. 500: glass gold firing temperature, mixed with glass accessories firing, gold layer content of about 5%-9%, easy to oxidize, not wear-resistant.

400 -600: baked imitation glaze, contemporary often with pigment spraying, printing treatment, commonly known as baked glass coating, applied to transparent white glaze, imitation red and yellow porcelain and gold edge can be real. High-temperature ceramics in the daily field:

In the daily use and craft collection porcelain, high-temperature porcelain refers to the glaze with a firing temperature of more than 1300, and the traditional porcelain such as underglaze blue and white and glaze red in ancient China are all made at high temperature. Ceramic enamel is a triangular conical chemical bond structure stabilized by silica, and only above 1250 can there be changes at the molecular level, so that the colorant is stably placed within the molecular structure. Therefore, high-temperature porcelain has irreplaceable unique effects in terms of color, color, and material density.

An item made by roasting at a high temperature of about 1000 to 1200 degrees.

1. Black pottery is used in the early stage of roasting, oxidation flame is used in the early stage, and the kiln is almost finished with smoke (at this time the flame is a reducing flame), and after a short time of penetration, it will appear black. The firing temperature is around 1000 °C. The surface of some black pottery is black and shiny, and the carcass is as thin as an eggshell.

White pottery is a white pottery fired from kaolin, with a delicate and hard tire and a firing temperature of about 1000.

2. In the south of the Yangtze River and the southeast coast of our country, a unique printed hard pottery was also unearthed, and after that, people also created and burned the pottery with glazed on the surface, called glazed pottery. There are two common kinds, one is that the tire is gray, the tire is hard, the surface of the vessel is gray transparent green glaze, and the firing temperature is 1200 glazed pottery. Its physical properties are close to porcelain, the raw material is kaolin, the water absorption rate is very low, the heat is 1200, and there is a metallic sound when knocking.

Therefore, this glazed pottery is called primitive celadon. The other is that the tire is red, and the surface is green, yellow, and yellow-brown low-temperature glaze, and there is lead as a flux in the glaze, so it is called lead-glazed pottery. It has appeared in the late Western Han Dynasty.

Tang Sancai is low-temperature glazed pottery.

3. Dry at a temperature of 60-70, then preheat to 600, then heat at a high temperature of 1200-1300, and finally cool down. When firing the dishes, the kaolin, potassium feldspar, sodalite, etc. are crushed, stirred into a dough shape, and pressed into a blank by the machine according to the shape of the dishes, and a batch of dishes is fired in 6 hours at the earliest, and it takes more than 10 hours for the thicker ones.

Production sequence: It is introduced from four aspects: mud mixing, molding, glaze matching, and calcination.

1. Mix mud. The purpose of mud blending, on the one hand, is to remove impurities, on the other hand, it is to match the soil with different origins and different molding and calcination properties into cooked soil that meets the needs of the maker, has a certain firing temperature range, and can echo the glaze and calcination temperature. Sometimes, in order to strengthen the supporting force of the mud in the case of high temperature calcination, so that the green body will not collapse, some sand is properly infiltrated.

Sometimes in order to pursue the color of the clay after firing, some coloring raw materials are added"Color tires"。The chemical composition of clay and porcelain clay is basically the same, due to the reason of weathering and re-weathering, their physical properties have been changed, so that the clay has greater viscosity and plasticity, and the porcelain clay has brittleness and a greater degree of vitrification at high temperature.

2. Molding. The preparation for drawing the blank is to knead the mud: that is, to put the mud ball in the center of the car surface, after the roller is rotated, use the opposite force of the wrist and fingers to grasp the mud ball in the center of the circle, and then repeat the mud ball with both hands several times up and down to make it further eliminate the bubbles inside and make the mud more"cooked"。

3. Glazing. Glazing methods: dipping, glazing and spraying.

Dipping glaze is to soak the whole body in a thin and suitable glaze, so that it is naturally adsorbed to a certain thickness. Glazing is to use a brush dipped in glaze and then apply it to the body, and a special effect will also appear when rubbing with the side of the pen. Spraying glaze is to spray the glaze on the body with a sprayer.

4. Calcination. Calcination is the last and most critical step.

1200 or more.

Firing porcelain must meet three conditions at the same time:

First, the raw materials for porcelain making must be porcelain stone, porcelain clay or kaolin rich in minerals such as quartz and sericite;

Second, the firing temperature must be above 1200;

The third is to apply the glaze fired at high temperature on the surface of the vessel.

First, the firing temperature is different.

The firing temperature of pottery is generally lower than that of porcelain, and the lowest even reaches below 800 and the highest can reach about 1100. The firing temperature of porcelain is relatively high, most of them are above 1200, and some even reach about 1400.

Second, the degree of hardness is different.

The firing temperature of the pottery is low, the body is not completely sintered, the sound is questioned when striking, the hardness of the carcass is poor, and some can even use a steel knife to cut out grooves. The firing temperature of porcelain is high, the carcass is basically sintered, the sound is crisp when striking, and it is difficult to draw grooves on the surface of the carcass with ordinary steel knives.

Third, the use of raw materials is different.

Pottery can be made from ordinary clay to make billets and fired, while porcelain needs to be made of specific materials and made from kaolin. The firing temperature is at the temperature stage required for pottery, and it can become pottery, for example, white pottery in ancient times was fired in this way. At the temperature at which the kaolin is fired is made, the body becomes porcelain.

However, when the clay used to make pottery is burned, it cannot become porcelain and will be melted into glass.

Fourth, transparency is different.

Even if the body of pottery is relatively thin, it is not translucent. For example, the black pottery of the Longshan culture is as thin as an eggshell, but it is not transparent. The carcass of porcelain, regardless of its thickness or thickness, is translucent.

Fifth, the glaze is different.

There are two types of pottery: unglazed and glazed, and the glaze of the glazed pottery can be melted at a lower firing temperature. There are two kinds of glazes for porcelain, which can be fired with the carcass at a high temperature, or hung with a low-temperature glaze on the high-temperature plain tire and fired at a low temperature for the second time.