Post #9280 by Saint-Thomas on Thu, Sep 26, 2002 8:20 AM

A word about crazing. Crazing is considered bad by those who don't like it. Those who do like it call it "crackles" glaze. Tiki-King is partly right about its cause, but the conditions that made the glaze not fit were during the firing. Cracks that appear later were already weak spots.
I see a lot of slip cast pieces with a white liner glaze go crackly after a few uses because the owner didn't read the warning about dishwasher or microwave use. Crazing should still be 100% functional and will leach neither more nor less impurities or chems than a stable glaze. However, they should not be used in the microwave or dishwasher since the crazing can allow small amounts of water to become trapped. If it were to be suddenly heated up to gaseous state, then BOOM! SO... sugarcaddydaddy, Keep on using your mugs without fear, but don't microwave them and they'll last longer.
BTW, just because the glaze looks like "good glass" doesn't mean it's foodsafe. However, no responsible ceramist would be using lead on dinnerware these days.
Crazing=bad, Crackles=good. same thing really.