My pizza stone cracked in half while I was making bread today. When baking loaves I steam the oven with a pan of water on the bottom rack then I spray the oven 2X at 30sec intervals. The loaves come out beautiful. This was the first time I tried it with the stone. It was for French bread so it started at 500 and then after spraying I lowered it to 450. This process of creating a "hearth" oven at home is from numerous books I have on bread baking and they all call for steaming the oven and using a stone to bake on. Where am I going wrong?