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Chinese porcelain is porcelain, a type of ceramic, from China and has been created for well over a millennium. The term covers a wide range of Chinese high-fired ceramics, some of which would probably not be recognized as porcelain under some Western definitions of that term. It is usually green-fired or once-fired, which means that the body and the glaze are fired together. After the body of a piece is formed and finished it is dried, coated with a glaze, dried again and fired. In the high temperature of the kiln the body and the glaze are fused together to become a unit.
Chinese enamelled wares are also produced in this way, but the enamels are added after the first, high-temperature, firing and the pieces are sent for a second firing in a smaller, lower-temperature kiln. Suitably modified with a flux, the material used to form the body of a piece of Chinese porcelain was often used as a glaze. The similarity in composition of the body and the glaze helped to produce a good fit between the two that reduced cracking in the glaze.
Chinese porcelain is mainly made using porcelain stone, china clay or a combination of the two materials. Both rocks derive from the weathering and decomposition of granitic rocks. China clay (Gaoling) largely comprises the clay mineral kaolinite. Chinese porcelain stone, petunse (baidunzi), is a micaceous rock containing sericite and other minerals including quartz (Kerr and Wood 2004). Porcelain stone often occurs kaolinised to a greater or lesser extent.
Porcelain stone and china clay are both composed of platy minerals, which is to say that they are composed to varying degrees of small platelets of high surface area (external and internal) and are capable of holding relatively large amounts of water. This is of importance because some of the methods used for forming the body parts of ceramic pieces (throwing on a wheel, for example) depend upon the application of compression to align the platelets and increase the plasticity and workability of the clay body. In the case of throwing, compression is applied by the hand of the potter.
In the West whiteware ceramics includes the categories of earthenware, stoneware or porcelain, depending largely upon the composition of the body and the kiln temperature required for its firing. However, the Chinese tradition recognises only two primary categories of ceramics, high-fired [cí 瓷] and low-fired [táo 匋] (Pierson 1996). The oldest Chinese dictionaries define porcelain [cí 瓷] as "fine, compact pottery" [táo 匋] (Bushell 1977). In the West the property of translucence is often regarded as a defining feature of porcelain, but this is not the case in China, where any thick or opaque piece that rings with a reasonably clear note on being struck would be regarded as porcelain [cí 瓷] (Bushell 1977).
Chinese ceramic wares are also often classified as being either northern or southern, so called because present day China comprises two separate, and from the geological point of view distinctly different land masses, the northern and the southern. The two land masses were brought together by the action of continental drift, forming a junction that lies between the Yellow river and the Yangtze river. Geological differences between the northern and the southern land masses have influenced the nature of the ceramic wares made in the two areas and, for example, in the north ceramic wares tend to have bodies made with clays, in the south ceramic wares tend to have bodies made predominantly of porcelain stone. In turn, this led to the development of coal-fuelled kilns suitable for the slow, high-temperature firing of clay-rich wares in the north and wood-fuelled kilns more suitable for the faster, lower-temperature firing of the stone-rich southern wares.
A Chinese Ming Dynasty cylindrical porcelain vase, dated to the early 15th century, Freer Gallery of Art.