Symptoms: Fine cracks spread throughout Solution: Add 5 percent silica to the glaze to stop crazing or 2 percent zinc oxide. Be careful with zinc-it could change the colour of you glaze. Adding 5-10 percent kaolin (china clay) to your glaze can also prevent crazing. Never fire under 1000 deg C for a bisque firing. 1060 deg C for a bisque firing. 1060 deg C is a preferred bisque temperature. Include a soak for 30 minutes to allow all the carbons and gases to escape. Bisque porcelain to 1100 deg C and earthenware to 1060-1100 deg C.
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