Porcelain is a ceramic material made by heating materials including kaolin, in a kiln to temperatures between 1,200 and 1,400 °C. The toughness and translucence of porcelain, relative to other types of pottery, arises from vitrification and the formation of the mineral mullite within the body at these high temperatures. Though definitions vary, porcelain can be divided into three main categories: hard-paste, soft-paste and bone china; the category that an object belongs to depends on the composition of the paste used to make the body of the porcelain object and the firing conditions. Porcelain evolved in China and was achieved at some point about 2,000 to 1,200 years ago slowly spread to other East Asian countries, Europe and the rest of the world, its manufacturing process is more demanding than that for earthenware and stoneware, the two other main types of pottery, it has been regarded as the most prestigious type of pottery for its delicacy and its white colour. It combines well with both glazes and paint, can be modelled well, allowing a huge range of decorative treatments in tablewares and figurines.
It has many uses in technology and industry. The European name, porcelain in English, comes from the old Italian porcellana because of its resemblance to the surface of the shell. Porcelain is referred to as china or fine china in some English-speaking countries, as it was first seen in imports from China. Properties associated with porcelain include low elasticity. Porcelain has been described as being "completely vitrified, impermeable, white or artificially coloured and resonant". However, the term "porcelain" lacks a universal definition and has "been applied in an unsystematic fashion to substances of diverse kinds which have only certain surface-qualities in common". Traditionally, East Asia only classifies pottery into low-fired wares and high-fired wares, the latter including what Europeans call stoneware, high-fired but not white or translucent. Terms such as "proto-porcelain", "porcellaneous" or "near-porcelain" may be used in cases where the ceramic body approaches whiteness and translucency.
Hard-paste porcelain was invented in China, used in Japanese porcelain, much of the finest quality porcelain wares are in this material. The earliest European porcelains were produced at the Meissen factory in the early 18th century; the composition of the Meissen hard paste was changed and the alabaster was replaced by feldspar and quartz, allowing the pieces to be fired at lower temperatures. Kaolinite and quartz continue to constitute the basic ingredients for most continental European hard-paste porcelains. Soft-paste porcelains date back from the early attempts by European potters to replicate Chinese porcelain by using mixtures of clay and frit. Soapstone and lime were known to have been included in these compositions; these wares were not yet actual porcelain wares as they were not hard nor vitrified by firing kaolin clay at high temperatures. As these early formulations suffered from high pyroplastic deformation, or slumping in the kiln at high temperatures, they were uneconomic to produce and of low quality.
Formulations were developed based on kaolin with quartz, nepheline syenite or other feldspathic rocks. These were technically superior, continue to be produced. Soft-paste porcelains are fired at lower temperatures than hard-paste porcelain, therefore these wares are less hard than hard-paste porcelains. Although developed in England in 1748 to compete with imported porcelain, bone china is now made worldwide, including China; the English had read the letters of Jesuit missionary François Xavier d'Entrecolles, which described Chinese porcelain manufacturing secrets in detail. One writer has speculated that a misunderstanding of the text could have been responsible for the first attempts to use bone-ash as an ingredient of English porcelain, although this is not supported by researchers and historians. Traditionally, English bone china was made from two parts of bone ash, one part of kaolin and one part china stone, although this has been replaced by feldspars from non-UK sources, but for example Royal Crown Derby still uses 50% bone ash in the 21st century.
Kaolin is the primary material from which porcelain is made though clay minerals might account for only a small proportion of the whole. The word paste is an old term for both the fired materials. A more common terminology for the unfired material is "body"; the composition of porcelain is variable, but the clay mineral kaolinite is a raw material. Other raw materials can include feldspar, ball clay, bone ash, quartz and alabaster; the clays used are described as being long or short, depending on their plasticity. Long clays have high plasticity. In soil mechanics, plasticity is determined by measuring the increase in content of water required to change a clay from a soli
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