Porcelain Glaze, which has an ultimate analysis of: Silica 68, alumina 12, lime 14, soda/potassium 6. 39.6 FELDSPAR ra FELDSPAR 21.5 WHITING 14 BALL CLAY 9.7 CHINA CLAY i CHINA CLAY 29.1 SILICA 20.5 WHITING 31.5 SILICA If these glazes craze on any clay body, in this temperature range, it is extremely unlikely that it is caused by the glaze. e4