are fired at 2000F, so heating them to 800F will not drive off anything new.the only possible problem is if the silicon carbide contained heavy metals such as cobalt or nickel, but thats unlikely.Thanks I actually wound up dispensing of them a while ago, and found a place that was willing to send me plain old unglazed tiles.FWIW, when I ran my hand over the abrasive tiles, some of the bits of whatev