It's practically an urban legend: a man heats water in the microwave for a cup of instant coffee. While taking the cup out of the microwave, he notices the water doesn't have any bubbles...at which point, the water boils up and explodes, giving him burns on his face and hands. Is there any truth to this myth?
Technically, and somewhat surprisingly, yes! Microwaves are specifically designed to heat water molecules and to heat them very rapidly. This can end up heating the water faster than it can turn into vapor, causing it to become superheated. Bubbles of water vapor can then quickly form when the water is jostled as the cup is taken out of the microwave. This makes it boil up, seeming to "explode," as all the vapor is suddenly released.
But in reality, the conditions that make this happen are relatively rare. Unless it's brand-spanking-new, the cups we use to heat water in the microwave likely have scratches that create an uneven surface where water vapor bubbles will form. Superheating will also only happen if the water is microwaved for an excessively long time, far longer than is actually needed to heat the water (2-3 minutes).
To insure yourself against a boil-up, you can put a wooden skewer or other non-metal utensil in the cup of water to help diffuse the heat and act as a surface for bubbles to form. You can also let the water cool down for a minute in the microwave before moving the cup or adding anything into it. Or you could boil water on the stove!
Has this "exploding water" phenomenon ever happened to you?
More Information on Exploding Water:
• Can Microwaved Water Explode? from Chow.com (with Mythbusters video!)
• Exploding Water in the Microwave from Steve Spangler Science
• Boil on Troubled Waters from Snopes
Related: True or False? Which Kitchen Myths Can You Believe?
(Image: Flickr member Harish-Rao licensed under Creative Commons)
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Interesting - I didn't realize that tap water was immune from this phenomenon.
Distilled water does this exceptionally well.
Ha - I saw this as a bit piece on Dateline or something a few years ago, and it scared me :) They said you can just quickly stir or jostle the water in some way before it goes in the microwave, and it'll break that surface seal on the water and make sure this doesn't happen.
Meanwhile, my Mom has been microwaving water for her 2-3 cups of tea every day for years without any problems.
It happened to me, and I had 1st and 2nd degree burns all over my face from it (fortunately they healed well). I prefer heating water on the stove to this day.
You know this is always one of my worst nightmares - I rarely boil water in the microwave but when i do i am so gingerly around it haha. Good to know its a rare pheomenon..but knowing my luck...ugh it could become a normal occurence.
saer
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I always thought that on top of it needing to be a perfectly smooth glass, that it also needed to be distilled water, since tap water has impurities that would also allow for bubbles to form (or something like that).
I had this happen to me nothing to tragic but I was making water for hot chocolate. When I took the water out of the microwave and poured it into the hot chocolate mix it was a little volcano reaction of mix and water. Until then I was sure that it was a myth.
I never "heat" the cup that I am going to drink from. I heat water in a Tupperware or glass measuring cup, and then pour the water into the serving cup.
I have discovered that if you heat milk in the microwave for making cocoa, you should NOT put the cocoa and sugar in right after taking the mug of milk out of the microwave. It will bubble up over the sides of the mug and make a huge mess, also potentially burning yourself.
This question was explored on Mythbusters, and the conclusion was plausible. You need to have really clean (distilled) water and a really clean container for it to work....I'm guessing that in most cases, there's enough dirt around to prevent an "explosion" from happening.
Yes, this happened to me once years ago. I was actually trying to make coffee by boiling water in a container to add to a french press. It wouldn't boil, was taking forever when suddenly it exploded!
I was freaked out and then did a bit of research to help me understand what I'd seen.
i once had my water "burp" at me, enough to scare me into always swirling the container while it's still in the microwave before taking it out!
I had the water not only explode out of the cup, it did so once the microwave stopped, blowing the door open and shooting boiling water out of it. It scared the CRAP out of me and also I got 1st and 2nd degree burns.
I have had it happen, and been able to repeat it. I was using a glass measuring cup. to microwave water for use in my lunch - a Shin Bowl. We have a whole home water ionizer, or something, but this was tap water. I heated the water to boiling, but forgot to use it on time. When I did get back to it, I figured it would only take a few seconds to kick it back to a boil, but strangely, the water was completely still. So, I watched and waited. After about three minutes, about one third of the water shot out of glass container in one big bloop. I still had enough to make my soup, so I left it all to cool off before cleaning it up. There didn't seem to be that much spill given how violently it shot out.
What I think caused this was simply that the surface layer of the water got somewhat cooler than the water in the rest of the vessel. A microwave heats from within, so the surface tension kept the top on the water long enough to create a violent boil. I repeated it, in the name of science. I have recently acquired an electric fast boiling kettle, which is really fast and really great. It has an auto-shut off and will also shut off as soon as you lift it from it's base. Much better!
If you are still microwaving water, placing a single wooden chopstick in your boiling vessel should prevent this problem. Having something porous, like wood in the water helps keep it agitated, so that it heats more evenly. At least that's what Alton Brown said once. Still, if you like tea and instant soup, an electric kettle is a great investment.
this is why we had to put boiling chips in the beaker in chemistry class
unless it's distilled water, and you're actually heating it to boiling in a glass beaker it will not happen. So sleep soundly.
If however you are in a chemistry lab, and heating distilled water in a 1000 mL glass beaker, you'll need to add some boiling granules
...wow. (I'd never heard of this, but then, it would never have occured to me to use anything other than, y'know, the kettle for heating water either - unless of course the power was out, in which case the microwave would be useless too...)
Same or similar concept for supercooled water: http://www.youtube.com/watch?v=DpiUZI_3o8s&feature=related
Purified water with a smooth container can be cooled below 32 degrees without freezing. Any disturbance will cause it to instantly freeze.
I was at my friend's mom's house and she heated a cup of tea in a glass mug and as she walked across the room to hand it to me it exploded and glass and hot water flew everywhere. Fortunately, she was not burned.
All the people claiming tap water won't explode should have a rumble with all the people who have personally witnessed tap water explode.
Yup - I've done it with tap water. Scared the crap out of me.
when i was younger, i thought my mom told me that she heated up vinegar in the microwave to clean it (it works fine with just plain water - and then no ammonia vapors are produced either). anyway, i heated up vinegar for a few minutes, took out the cup - and BAM! exploded all over. luckily it did not get on my face, but it scared the living daylights out of me... i am always very cautious about heating any liquid in the microwave now.
I find this happens - but not a huge blow up - when I stick a spoon in the hot water when I pull it out of the microwave.
I do this every time I take it out, just to see if it will happen . . . sometimes it does, sometimes it doesn't. We do have a 1300 watt microwave, so really 2 minutes is all that's needed to boil the water.
This was on mythbusters. They proved it does happen with distilled water but tap water has enough additives in it to be safe.
Mythbusters was WRONG. I've had tap water explode with enough force to shoot over two feet. And the pain of boiling water on your hand, arm and chest is damnably unpleasant. It's rare, but it can happen. A scratched container helps and so does a wooden spoon or chopstick. Play it safe ... and use an electric kettle to heat water. It's very, very Canadian.
If you had water explode then you probably lived in some very mild water area, and or it was well filtered, and you probably heated it in a slick (aka glass, nonstick pan) container.
Milk does it as well if you add a spoon or something to the cup as soon as it comes out. Explode!