Back when I was a girl, I knew someone who made crackle-glass for jewellery craft projects by heating a wire frying basket full of glass marbles in very hot oil, then plunging the basket into a container of iced water. Very very carefully, and covering the container of iced water with a lid, instantly as the marbles went in, because you could sometimes get a marble that burst and shattered rather than cracking decoratively. Very hot flying glass splinters - not good. My grandmother used to insist he had to do it out in the barn in winter, which was the only time we had ice (no electricity on the farm).
Yuuago: caught fire?!? For how long did he microwave it?
OwlsG0: potatoes don't do that if you make a few holes with a fork first. Eggs, on the other hand, require a little pin device to pierce the membrane inside the shell, and even this doesn't always work. I discovered this quite by accident, upon my first attempt to use my husband's multitude of high-tech bachelor cooking gadgets when we were first married. I was used to a woodstove or open fires, or a camp oven, and my first try at a microwave succeeded in blowing up an egg quite spectacularly. I won't talk about what I did to his fancy non-stick cookware!
I still won't use a microwave for protein or dairy, because I find the result just smells wrong, and for me at least is completely indigestible.