Pizza stones are made to be put in the oven while it's preheating. The extra mass retains a LOT of heat, making for a more regulated oven temperature which equals more even baking. In addition, placing a pizza on the hot stone will directly transfer oodles of heat to the bottom for a nice crispy crust. If, however, you preheat the oven & then slap a frozen pizza on the room temp. stone & throw it in the oven; the stone acts as a big fat insulator. so the top of the pie gets blasted by hot air, while the bottom is completely shielded by the cool mass it rests on. This, of course, results in a pizza with a toasty bubbley top, and a soggy bottom.
Pizza stones are made to be put in the oven while it's preheating. The extra mass retains a LOT of heat, making for a more regulated oven temperature which equals more even baking. In addition, placing a pizza on the hot stone will directly transfer oodles of heat to the bottom for a nice crispy crust. If, however, you preheat the oven & then slap a frozen pizza on the room temp. stone & throw it in the oven; the stone acts as a big fat insulator. so the top of the pie gets blasted by hot air, while the bottom is completely shielded by the cool mass it rests on. This, of course, results in a pizza with a toasty bubbley top, and a soggy bottom.