So, boiling it is. As far as the bobbing around, or letting the glass contact the metal of the cookpot, I plan to jam some cheap sponges in the bottom of the pot to pad it. Then, put the glass in the cool water and bring it to a boil in the outer pot. I'll be using my gas range, but I think the water insulating the bottom of the interior pot will keep the bottom of the pot from taking the brunt of the heat of the flame. I've been more worried about ruining the coating than cracking the glass. I'll use some sort of stiff padded tool to "fish around" the glass to dsee if it is actuall separating. If it does, I'll kill the flame and let the water cool down naturally. Avoiding thermal shock is the best policy.