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Bone china (cultural art)
Bone china was invented by the British in 1794. It is named after the addition of bovine ash (such as bovine bone powder) to cows and sheep. The bone china color is natural milk white which is unique to natural bone powder.
Generally speaking, porcelain containing 25% bone powder in raw materials can be called bone china. The internationally recognized bone powder content is higher than 40%. The best quality bone china generally contains 45% high quality bovine bone powder. Among them, the bone powder component is more than 40%, and the color of the appliance is milky white, which is a high-grade bone china. The price of more than 40% of the bone china set tableware with good European standards is about several thousand yuan. There are not many brands that export high quality bone china.
The two basic characteristics of bone china are the essential basis for distinguishing between bone china and other porcelains. Feature 1: bone charcoal content of 36% or more (national standard); feature two: after secondary firing (sugar, glaze).
Source of bone china
Bone China is the only porcelain species invented by Westerners in the world and has been given a high value. In fact, the appearance of bone china is purely accidental. Strictly speaking, it is an unexpected result of a less successful imitation.
The invention of bone china in Cambridge History of China is described as follows: Ancient Chinese ceramics are of great value in the West, and their export history can be traced back to two thousand years ago. In Europe, the work of imitation ceramics has never been interrupted, but the real breakthrough is also due to the development of the Venetian glass industry.
Today, it is known that ceramics consist of three layers: the enamel layer, the bonding layer and the inner clay layer. The most difficult to imitate is the enamel layer. The Venetians invented lead glass in the fifteenth century, and since then many attempts have been made in this field. It has been found that the ceramic enamel layer is somewhat similar to glass.
In the seventeenth century, the thin porcelain of Jingdezhen in China was introduced to Europe. This is a shocking invention. The Chinese history book "Tao Ji" said this kind of porcelain: "thin as paper, white as jade, as bright as mirror, sound as磬". The European saying is: "It's thinner than paper, whiter than milk, and more transparent than glass" (literally).
This kind of porcelain is worthless in Europe. A piece of porcelain can even be exchanged for an army. Even more amazing is that this kind of porcelain can even be made into a lamp, but it has a more fantastic effect than a glass lamp.
In order to get the effect of "more transparent than glass", in 1794, the British inventor William Walson added animal bone powder to the clay. The bone powder can obtain calcium oxide after being subjected to high temperature, which is a very mature technique in the glass process. In order to obtain a creamy white color of thin porcelain, he added some aluminum powder.
Today's technology tells us that calcium oxide is one of the most important fluxes in glass manufacturing. It can effectively reduce the softening temperature of silica and make it easier to form glassy materials. Alumina is a commonly used opacifier, which even makes the glass appear less transparent milky white.
Soon, a European ceramic of its own was invented. Although it is difficult to reach the thickness of thin porcelain 1mm-2mm until now, and the color is slightly reddish, it can not really achieve high white color, but this is the only porcelain invented in the West, and its appearance is revolutionary. of. Since this ceramic adds a large amount of animal bone powder to the firing, it is called "Bone china", which is bone china.
Today's bone china has been improved many times. The basic formula is six ashes and four porcelain stones. Later, it gradually developed into fifty pieces of ashes, twenty-five porcelain stones and twenty-five pieces of clay. It has been in the UK until today. It is considered a standard formula.
Like the standard of artificial crystal, according to international standards, ceramics containing more than 25% calcium oxide can be called bone china.
Since it was founded in the UK, and the early bone china yield is very low, it has long been a special porcelain for the British royal family. Today, due to the needs of industrialization and the development of science and technology, people no longer use animal bone powder, but take a composite formula of calcium oxide and aluminum oxide, so that bone china can be owned by more people. However, the production of a very small number of high-grade bone china still uses some raw materials such as bone powder, and the value is generally hundreds of pounds or even higher.
The bone china is placed in the bright place for observation, and the bone china products with fine components and light-transparent impurities are preferred. Bone china is graded like ceramics and usually depends on the texture of the material, the manufacturing technique and the painted design. The higher the number of bone china, the more difficult it is to make and the more expensive the finished product.