Thanks everyone! This was a big help.

@timotheos: Thanks!

@ByrdBrain: It's a thin stone (a basic cheap stone, 1/2-3/4 inch thick), and I generally preheat for a little over an hour at 500 (the maximum for my oven) before I put the pizza on the stone. I don't have an infrared thermometer so I don't know the exact temp of the stone when I put the first pizza on.

The pizzas are being made right before they go in, so they're at room temp. I'm using the dough right after it's done rising so it's at room temp.

I'm really just looking for the stone to be hot enough so that I get a crunch on the crust the second time through. An infrared thermometer will definitely be on the wedding registry, but that's still more than a year off, so until then, I'll be flying blind.