Should stoneware pots be fired with the lid in place, or with the lid separated from the pots?

Generally, fire with the lid separated from the pot during the bisque firing; fire with the lid on during the glaze firing. If the lid is fired on the pot during bisque, the organics in the clay may become trapped inside the pot and not burn off completely. Fire the pot with the lid on during the glaze firing. The lid will help prevent the pot from warping, and the lid will fit better.