Bisque is clay that has been fired once, without glaze, to make it hard and porous enough to handle and glaze safely. The bisque firing is usually around cone 06 to 04, roughly 1000 to 1060 °C.
What Is Bisque?
The bisque firing turns fragile greenware into ceramic. It drives off the remaining water and burns out organic material, and the clay particles start to bond permanently, so the piece can no longer be slaked back into clay. It stays porous, though, which is exactly what potters want: dry glaze sticks to bisque because the porous surface soaks up water from the glaze slurry.
Bisque is usually fired lower than the glaze firing for stoneware and porcelain. Firing it too low can leave carbon and gases in the clay that cause pinholes later, while firing it too high makes it less absorbent and harder to glaze evenly.
Most kiln explosions happen during the bisque, because any moisture left in the clay turns to steam. That is why studios ask for bone-dry work and fire the early part of a bisque slowly. Bisqueware is also what paint-your-own-pottery studios sell, ready for underglaze and a clear glaze.
This pottery glossary entry from Le Studio Art Space is general educational content. Always follow the clay, glaze and kiln makers’ data for your own materials and equipment.