I use a stoneware clay that vitrifies at cone 6 (about 2232 degrees). pieces are thrown, trimmed completely dry I sand them and load them in the kiln for the first firing called the bisque.
The Bisque is fired to cone 05 (about 1800 degrees), Just hot enough so they have turned to stone yet not fired all the way so that they are still porous enough to accept glaze. Now it is time to glaze and fire again!
These are pieces that have been glazed but not yet fired. Now it's time to load the kiln and fire again. The Glaze firing takes about 14 hours.