Umm i very likely dought you are right on this one. THere are two things that causes pizza stones to crack:
1) Big temperature changes. Say you heat the stone to a scortching temperature on say a good gas grill that gets hot like a weber genesis. I know my grate temperature can get well passed 650. Anyways open the lid (especially when its cold out or if you open the lid all the way to let a lot of the heat out) and you could crack your stone.
2) Get something wet on the stone when hot. Say for example your sauce is to watery and it spills over on the stone. This definitly could cause a crack.
3) Lots and lots of use where it heats up and cools down. Of course this takes a long time especially with a good quality stone (thick).
The soap might cause a bad after taste but i very very unlikely it will cause the stone to crack.
Oh ya you might be able to soak your stone in water if you do have a soap after taste and as long as the soap residue disolves (might want to give a good soak time (48hours)) through the basic scientific principle of osmosis (the tendency of a substance to go from a area of higher concentration (your stone) to an area of lower concentration (the fresh water) until equilbrium is reached.). If you do this method you might want to flush with fresh water as often as you can to keep the soap moving from the stone to the water outside. If you do this make sure the stone thoroughly dries before you use it again (especially if you cook your pizza at rocket hot temperatures like i do 550F). Don't think because the stone is dry on the exterior that some of the pores could not have retained some of the moisture. It might be safer to put the pizza in the oven at its lowest temperature for 30 min to make sure its thoroughly dry before you try high temperatures again.
Hope this helps,
Originally Posted by Caine
Give me your pizza stone. Within a couple of weeks it will crack, and you'll have an excuse to buy a new one, which you WILL NOT WASH WITH SOAP!