Porcelain is a particular type of ceramic , which is obtained from mixtures containing kaolin and feldspar and by firing at temperatures between 1300 and 1400 °C.
The open porosity is zero, the closed one can reach values of even 5%. The material is of vitreous phase, so the crystalline component does not exceed 40%. Porcelain is divided according to different criteria, one of which is the firing temperature. Hard porcelain is formed by a mixture of kaolin , feldspar and quartz and requires a temperature higher than 1280 °C; soft porcelain is fired around 1200 °C. Porcelain has a transparent coating that is applied in the raw state or after an initial firing at temperatures between 800/900 °C. The pre-fired product for enamelling is called degourdi .
The components of the coating are the same as those of the body, but in proportions that give the mixture greater fusibility. For a greater degree of whiteness, the porcelain is fired with an initial heating period in an oxidizing atmosphere, a high-temperature phase in a reducing atmosphere and a cooling process in a neutral atmosphere.
