1 Answer

Generally, bisque firing is done between cone 08 and cone 04, no matter what the maturation temperature of the clay and of the glazes that will be used later.

By cone 08, the ware is sintered and has become a ceramic material. At the same time, the clay body still is quite porous and absorbent enough for easy glazing. It does remain more fragile, however, and extra care will need to be taken when handling this bisqueware. http://pottery.about.com/od/firingthekiln/tp/bisqfire.htm

Bisque firing can be done up to cone 04. While this makes the bisqued pots a bit less fragile, it can increase glazing time and may adversely effect glaze adhesion, as the pot's fabric has tightened and become less porous and absorbent. The higher the temperature, the less porous the ware becomes.