You could always throw in an uncracked egg or ball of tin foil....

The first egg I ever tried to "boil" in a microwave was punctured - and blew up spectacularly anyway.

I heat my water in the microwave all the time, and while I've had superheating happen, it's rare.

Movement also helps prevent the explosion. Give the mug a bit of a swirl when you place it in the microwave. Better yet, use a microwave with a turntable.

I also heat my water in a teapot with a lid, so if super heating happens, the worst that will happen is that water will come out the spout. But in the 6 years I've been heating water daily for coffee in the microwave, I've only had it happen once or twice, and it was always at work, where there was no turntable (and I switched to a tiny teapot there).

tohenk2 wrote:The first egg I ever tried to "boil" in a microwave was punctured - and blew up spectacularly anyway.

I think they all do no? Its fun to watch if its not your microwave.

Aha! Maybe it's the turn table that saves me. I make 2 Americanos every morning by heating up 2 cups a little less than half full of water for 85 seconds while I grind the coffee. It's a not so delicate dance, back and forth in the kitchen. When the first basket is ready for the portafilter the water is just right. So far, so good.