Despite all the high-tech equipment in kitchen shops today, one of the best tools for making better bread and pizza is still the decidedly low-tech flat stone. A baking stone (also called a pizza stone) is a ceramic tile made from natural clay that’s been pressed into a dense, flat shape (round, square, or rectangular) and kiln-fired at extremely high temperatures. Like the bricks that line chimneys, baking stones retain and radiate heat while remaining fireproof and resistant to warping or cracking. Cooks put the stone on the lowest rack of the oven (or directly on the floor of a gas oven) to replicate the brick floor of a traditional baker’s oven.
There are three advantages to baking on a stone. First, when you’re making breads and other leavened baked goods that need an initial push of heat to rise properly (called oven spring), the hot surface of a stone provides a direct thrust of heat that the heated oven air can’t. Second, in the case of doughs cooked directly on the hot stone, the stone’s slightly porous surface draws moisture from the dough to produce a more definitive, crisp, and tasty bottom crust. At the same time, the stone disperses this moisture as steam, which promotes a lighter top crust. Finally, a thoroughly heated stone also provides a consistent source of radiant heat, despite fluctuations or hot spots in your oven.
This final reason is why many cooks leave a stone in the oven full-time. While its effects won’t be as dramatic on foods that aren’t cooked on the stone, it will promote a more even oven temperature.
A stone heats up slowly and cools down just as slowly, so to get the best results from your stone, put it in a cold oven, set the temperature, and wait for 30 to 45 minutes (or wait until 20 minutes after your oven reaches temperature) before baking on it. The thicker the stone, the longer it will take to heat up.
Unglazed quarry tiles (pavers) can make fine baking stones. Sold at tile distributors, they’re inexpensive and provide a little more flexibility, but be sure to buy tiles that are unglazed and lead free (the best guarantee is to buy American-made tiles, which are lead free by law). As for size, you’ll need to leave at least 1-1/2 inches between the edges of the stone and the oven walls for air to circulate.