Porcelain clay is essentially composed of three types of rock:
- kaolin provides the white hue and plasticity for shaping
- quartz acts as a degreasing agent, reduces deformation during firing and allows the piece to retain its shape
- feldspar is needed for glazing and gives porcelain its translucent quality.
Several steps are required to produce porcelain :
The raw materials (about a dozen other ingredients are added to them) are crushed and mixed. The resulting clay is then filtered and sifted.
The clay is shaped using several different techniques
Gauging is used only for circular pieces.
Casting is used for complex pieces. Liquid porcelain clay is poured into hollow plaster moulds.
Once the piece has been shaped, it is dried by firing it at a temperature of 980°. Since the piece is now porous, it is enamelled by aspersion or by immersion in a liquid enamel bath with a fine mixture of mineral compounds.
Next, the piece is fired again at 1400°, the temperature at which the fusion point is reached. The porcelain is now hard and no longer porous, resulting in unsurpassed sanitary quality for tableware.
The porcelain artists of Limoges are renowned for the remarkable translucent quality of their work.
