Has Cecil or the Straight Dope Staff tried duplicating this effect in a scientific experiment? I ask because it seems like they are just reporting what others have said.
I’ve had water explode very violently before. I was making tea in a tall glass. I heated the glass and water (no tea added) for around 4 minutes. Just before the time was up, there was a loud “pop” sound and the water exploded with a massive burst of steam. The microwave door blew open with such a force that it swung around and hit the cupboard next to the microwave leaving a deep dent where the handle hit. I was wacthing it very closely the whole time until it exploded, fortunatly someone came and distracted me just before the explosion. (Or I would have been that guy in the netlore email)
Some interesting things to note:
I watched it while it was heating in the microwave, no bubbles formed other than a few very small ones on the side of the glass.
I was using well water which had high mineral levels, especially high levels of Iron. (this is unusual because distilled water is supposed to be better for this)
There was very little water left after the explosion. There was about an inch in the glass and only a couple paper towels worth in the microwave, counter, floor, etc.
Ive duplicated this several times with the well water, distilled water, etc, but never as violently as the first.
This has little to do with the subject at hand, but it’s (I think) and interesting story and has to do with a microwave.
I used to have a habit of soft-boiling eggs in the microwave. I would crack two eggs into a cup, and nuke them for a little while, and then salt and stir them before eating. This gave me more consistent results than simply boiling the eggs.
I did this every day for weeks with no consequence. Until…
One day my sister was over and told me that what I was doing wouldn’t work. The eggs would explode, she said. I replied that, her theories aside, I had done this dozens of times with no ill effects, thank you very much.
Well, that was all it took.
Apparently the microwave fairy considered this fair warning and decided today was the day I was to get it. The second the fork entered the cup, the eggs exploded violently, emptying the cup all over my tie, shirt, face, and the ceiling. There was less left in the cup than there would have been had I eaten it.
To this day, I say it was all my sisters fault for informing me. While I was ignorant, it worked fine. The minute I was educated, I was hosed.
I’ve had water wait till I took it out of the microwave to boil. I put tap water in a clean coffee mug and put it in the microwave for long enough to boil. When I opened the microwave door, the water was still, until I picked up the cup. Then the water started bubbling like soda. It was really cool, I thought, and didn’t so much as spill over the edge of the cup.
As for foxfire’s thing, Maybe the microwave had a problem? Like if it wasn’t able to vent the steam (clogged vents or someting) then the pressure would build until it pushed the door open. I don’t know if the change in pressure with the door opening would be enough to open the door. Did you put the water in for much longer than it needed to boil for? Maybe if you build up enough energy past the boiling point, you get a lot more than the fizz I witnessed.
I too have had this happen (in a ramekin dish, which has a wider surface area). I figured that the skin had formed on the top and the steam pressure had built up underneath, eventually leading to a very loud explosion (scary as all hell breaking loose, although not as bad as Steven Seagal’s exploding microwave in “Under Siege” - wonder if that was an egg too? ;)).
Anyway, I haven’t cooked with a microwave since 1988 - go figure.
Second, nucleation.
This also happens when you have heated water to too high a temperature (boiling, and then some), and then throw in a large amount of salt (like when you make pasta). How can this be right? I remember from physics that introducing an impurity raises the boiling temperature i.e. the water should have gone off the boil(?).
BTW, I don’t recommend anyone goes out and tries these, since plastic surgery doesn’t come cheap…
Funny thing, I just read about this on another site. Some syncronicity here?
check out http://rabi.phys.virginia.edu/HTW/ and look at the November 15, 2000 entry. The guy there conducted an experiment and even video taped it. You can watch the results, too. Basically, he superheats a cup of water in a microwave and drops a fork into it to start the nucleation and repeated those steps. Most of the time, it just bubbled up. On the 13th try, the water explodes and leaves almost no water in the cup.
So, the real explosion only happening 1 in 15 tries, seems to suggest that this is uncommon. Also, he put a little vegetable oil to prevent evaporation.
Also, for those interested in the Strait Dope, this is a similar site, as far as answers for your questions, but probably not as open to questions outside a scientific nature.
I just wanted to add my two cents to the subject. I’ve had water explode in my microwave ( this was when i was probably trying to make jello, i never have any luck with that).
I had put two cups of tap water into my pyrex glass measuring cup, and put it in the microwave. I remember getting mad because it wouldn’t come to a boil, and I stood there seething at it when I heard this loud BAM as a cup and a half of the water suddenly exploded all over my microwave.
I cleaned up the mess and gave up. I figure, if you can screw up boiling water, its time to go back to bed.
I had never heard this as an urban legend or otherwise, but I had nearly exactly what the original message claimed happen to me when I was in high school (about 12 years ago). I had a cold, and I put a bowl of water with a menthol ointment floating on it in the microwave, not for a terribly long time as I recall. When I took it out I immediately held it up to my face to inhale it, and it jumped out of the bowl and onto my face. The grease factor in the ointment worked to hold the heat in so that by the time I got cold water on my face I had 2nd+ degree burns. I stayed home from school for two weeks because it was hideous! Anyway I always assumed that the ointment made a “skin” on top of the water, and held the heat in until my breath blew on it and caused a reaction. But whatever the cause, I’d be willing to testify before a judge that it CAN happen!!
From looking at that video, I noticed that on #13 there was noticeably less liquid in the cup than on other tries because on #12 a lot of the liquid flew out. So if the water was zapped for the same amount of time as #12 (which can’t be determined from the video), it would be hotter. This probably means it’s easier for this to happen with a smaller amount of water because it heats faster.
Great site and video, alandowney - a great way to introduce yourself. And thanks to all for your personal experiences. Welcome to the SDMB!
While it is true that water with solutes disolved in it will boil at a higher temperature than distilled water, this effect is not important with microwaved water. After heating water in a microwave for several minutes it is already well above it’s impure boiling point. It doesn’t start to boil because the bubbles have no place to form. The salt crystals provide excellent sites for bubble formation. Cecil explains this more fully in his column: