What is the ideal bisque firing temperature to use?

The biscuit firing temperature that is chosen should either give the clay sufficient strength to withstand the glazing process, or fire the clay to maturity prior to glazing. It is essential to mature the clay during the firing process to prevent crazing of the glaze. Stoneware and porcelain clays can generally be fired to 1000oC at biscuit stage because the clay will be fired to maturity during the glost firing. Earthenware clays, like all clay bodies, need to be fired to maturity in one of the firings but it doesn’t matter whether this is done in the biscuit or glaze firing. What governs which firing is quite simple to determine. If the glaze to be used will fire to a temperature which lies within the maturing range of the clay, then a low biscuit/high glost format can be used. However if the glaze firing temperature is lower than the maturing range of the clay, then a high biscuit/low glost format must be used. Bone China is the ‘odd one out’ because it must be fired to a high biscuit temperature of between 1200oC and 1250oC, followed by an earthenware glaze firing.