The Chinese glaze is also the more fusible, on account of the addition of lime to the petuntse, which the French use pure.
It is not, therefore, composed simply of kaolin and petuntse.
The manufacture of hard porcelain was begun at Svres in 1769, the quarries of St. Yrieix supplying both the kaolin and petuntse.
The kaolin and petuntse used in making paste for Chinese porcelain are chemically identical with the materials used in Europe.
Chemically, petuntse resembles the pegmatite of Limoges; mineralogically, it is to be classed with petrosilicious felspar.
Kaolin and petuntse are of little importance in the composition of soft porcelain.