An introduction for porcelain

Porcelain is a ceramic material made by heating raw materials, generally including clay in the form of kaolin, in a kiln to temperatures between 1,200 °C (2,192 °F) and 1,400 °C (2,552 °F). The toughness, strength, and translucence of porcelain arise mainly from the formation of glass and the mineral mullite within the fired body at these high temperatures . Porcelain derives its present name from its resemblance to the cowry, which in old Italian was called porcella, meaning little pig. 
Properties associated with porcelain include low permeability and elasticity; considerable strength, hardness, glassiness, brittleness, whiteness, translucence, and resonance; and a high resistance to chemical attack and thermal shock. 
For the purposes of trade, the Combined Nomenclature of the European Communities defines porcelain as being "completely vitrified, hard, impermeable (even before glazing), white or artificially coloured, translucent (except when of considerable thickness) and resonant." 
However, the term porcelain lacks a universal definition and has "been applied in a very unsystematic fashion to substances of diverse kinds which have only certain surface-qualities in common" (Burton 1906). 

Porcelain is used to make table, kitchen, sanitary, and decorative wares; objects of fine art; and tiles. Its high resistance to the passage of electricity makes porcelain an excellent insulator. It is also used in dentistry to make false teeth, caps and crowns. The following section provides background information on the methods used to form, decorate, finish, glaze, and fire ceramic wares. 

Forming 

The relatively low plasticity of the material used for making porcelain make shaping the clay difficult. In the case of throwing on a potters wheel it can be seen as pulling clay upwards and outwards into a required shape and potters often speak of pulling when forming a piece on a wheel, but the term is misleading; clay in a plastic condition cannot be pulled without breaking. The process of throwing is in fact one of remarkable complexity. To the casual observer, throwing carried out by an expert potter appears to be a graceful and almost effortless activity, but this masks the fact that a rotating mass of clay possesses energy and momentum in an abundance that will, given the slightest mishandling, rapidly cause the workpiece to become uncontrollable. 

Glazing

Unlike their lower-fired counterparts, porcelain wares do not need glazing to render them impermeable to liquids and for the most part are glazed for decorative purposes and to make them resistant to dirt and staining. Great detail is given in the glaze article.Many types of glaze, such as the iron-containing glaze used on the celadon wares of Longquan, were designed specifically for their striking effects on porcelain. 

Decoration

Porcelain wares may be decorated under the glaze using pigments that include cobalt and copper or over the glaze using coloured enamels. Like many earlier wares, modern porcelains are often bisque-fired at around 1000 degrees Celsius, coated with glaze and then sent for a second glaze-firing at a temperature of about 1300 degrees Celsius or greater. In an alternative method particularly associated with Chinese and early European porcelains, the glaze is applied to the unfired body and the two fired together in a single operation. Wares glazed in this way are described as being green-fired or once-fired. 

Firing 
In this process, green (unfired) ceramic wares are heated to high temperatures in a kiln to permanently set their shapes. Porcelain is fired at a higher temperature than earthenware or stoneware so that the clay can vitrify and become non-porous.