Originally Posted by citanon

Many a year ago I was heating some water in a glass container using my parents' microwave. I fille the container with about half a liter of water and walked away to join my folks at the dinner table.

Two minutes later, there was a tremendous boom and steam puffed out from the now defunct microwave's every opening. Upon closer inspection, we were very lucky that our high quality Panasonic had contained the explosion, which included flying glass shards from what was our glass pot and an alarming amount of superheated steam.

This taught us all a lesson: when boiling water inside a microwave, you NEED to add small particulates to nucleate the boiling process. Otherwise, even heating of the water by the microwave, together with the featureless surface of glass containers, could result in superheated water, which, when slightly perturbed, would give the kind of explosion that destroyed my parents' microwave. Imagine if this had happened when I went to get the water.