A-Z of Ceramics - H is for Hard-paste
Hard-paste or 'true' porcelain is so-called because its raw materials and firing temperature (1200°C to 1450°C) result in a very hard, strong body that can withstand boiling water. Its other desirable qualities are whiteness, translucency, resonance and non-porosity. It moulded details are often crisper than those in other wares.
The recipe and firing technique was invented in the 6th century in China, where there was plenty of kaolin (china clay) and petuntse (fusible feldspar rock), its two ingredients. China kept the recipe and method of production a closely guarded secret while Europe struggled to discover the ingredients. In 1709, after years of research, the physicist E.W. von Tschirnhaus and the alchemist J.F.
Böttger produced hard-paste porcelain, leading to the foundation of the Saxon royal factory at Meissen in the following year. Böttger had been virtually kept a prisoner by Augustus the Strong, Elector of Saxony, until he discovered the great secret or 'arcanum'. Like the Chinese, the Meissen factory hoped to keep the secret to themselves, but industrial espionage by rival 'arcanists' led to the dissemination of this 'secret knowledge'.