A pizza stone is a flat stone or piece of ceramic or earthenware used to evenly distribute oven heat to pizzas or other baked goods, more or less mimicking the effects of cooking a pizza in a masonry oven. Such bakeware has more thermal mass than metal or glass pans. The porous nature of the stone used also helps absorb moisture, resulting in a crisp crust.
Small pizza stones can be purchased to fit in any conventional cooking oven. High-end ovens sometimes offer optional pizza stones that are specifically designed for each oven model and may include a specialized heating element. A home made "pizza stone" can also be made by distributing one or two layers of unglazed tiles on top of an oven rack (being certain the tiles are lead-free).
To prevent fracturing of the stone by thermal shock, the pizza stone should be placed on a cold oven and heated over at least 45 minutes, and it should be allowed to cool down slowly inside the oven after switching it off. Because of the possibility of rapid temperature change, pizza stones should not be left in an oven while it is in self cleaning mode.
Some cooks recommend sprinkling cornmeal, semolina or bread crumbs on the pizza stone to prevent the crust from sticking.
Because they are porous, pizza stones will absorb any fluid with which it comes into contact, including detergent. They should be cleaned with a dry brush and then plain water.