Another thing that promotes a crispy crust is steam. Commercial bread ovens have steam injectors (and I hear tell some high end residential ovens do too) but you can approximate it by squirting water into the oven as soon as your pizza is on the stone. You can buy a spray bottle (99 cents at Target) and fill it with water. Squirt some on the walls of the oven to generate steam and/or spray some directly on the dough.
Jock |