Note to newbie: Do not boil vinigar in microwave in glass jar. I did
once and the contents exploded out of the jar. I was covered in a
quart of boiling hot vinigar. Not fun. The jar was in one peice, the
contents just blew out. And I mean BLEW OUT.

Later I've heard about keeping a wooden stirrer in the liquid and you
can do it in the microwave. Sorry, I'm not going to do that again.

I understand that you can do the same thing with water too. Apparently
you need to be sure that there is something in the jar to act as a
nucleation site for the bubbles to start forming on. Otherwise you
get superheated liquid that suddenly boils as soon as it is disturbed.
I guess we're lucky that most glassware isn't that smooth (or perhaps
they're made rough on purpose?).