Did you know that heating water in the microwave can actually be dangerous? While sharing this story with audiences, I’ve learned that many people have had similar experiences but never understood why the water just blew up. It’s an important piece of science to share with others in hopes of preventing a potential disaster.

There's a danger to boiling water alone in the microwave - it could explode if no bubbles are present. | Steve Spangler Science Blog

The American Burn Association (ABA) has identified scald burns from superheated liquids in microwaves as a target for a new public awareness campaign… “Water alone should never be heated in a microwave.” Here’s why…

Water Can Explode in the Microwave

This is an all too common example of what can happen. A man decided to have a cup of instant coffee, so he heated a cup of water in the microwave. When the timer went off, he removed the cup from the microwave and noticed that the water had not boiled.

Just then, the water literally “blew up” in his face. His whole face was blistered with first and second degree burns, which left some permanent scarring and damage to his left eye. While at the hospital, the doctor attending him stated that his is a fairly common occurrence. Water alone should never be heated in a microwave oven.

Why? This phenomenon is known as superheating. It can occur anytime water is heated – especially if the cup or bowl is new. What happens is that the water heats faster than the vapor bubbles can form. If the cup is very new, then it is unlikely to have small surface scratches in it that provide a place for the bubbles to form (called nucleation sites).

There's a danger to boiling water alone in the microwave - it could explode if no bubbles are present. | Steve Spangler Science Blog

Without bubbles, the water cannot release the heat that has built up, the liquid does not boil, and it continues to heat up past its boiling point. If the water is bumped or jarred, it’s enough of a shock to cause the bubbles to rapidly form and the result is an exploding liquid that is scalding hot. One solution is to place a wooden stir stick or something non-metallic in the water to help diffuse the energy as it is heating in the microwave.

Burns from Boiling Water in the Microwave

Dr. Gordon Lindberg, MD, PhD, and director of the burn unit at University of Colorado Health Sciences Center, agrees that the phenomenon of superheated liquids is a real problem. According to Dr. Lindberg, the American Burn Association (ABA) has identified scald burns from superheated liquids in microwaves as a target for a new public awareness campaign.

“These burns are dramatic and traumatic because they often affect the face and hands of the burn victim. Fortunately, these burns rarely need grafting; however, they are extremely painful and in children these burns often lead to hospitalization for wound care and pain control. The best way to avoid these burns is to place a wooden coffee stirrer in the liquid when heating it and also to let all heated liquids cool for a few minutes inside the microwave before removing them,” explains Dr. Lindberg.

If you receive one of these burns, and especially if it covers the face or hands, seek a burn care specialist for care. Initial treatment for the burn can be performed in an ED or at a doctor’s office, but a burn specialist should see the burn within 24-48 hours after the injury, especially if the face is involved. If the eyes are involved, an ophthalmologist should be consulted immediately.


51 replies
  1. none
    none says:

    Hmmmm… Ive heard of this before but i didnt belive that it could actully happen. So what that says that if a new cup is used to heat water its lickely that the water will explode. This is very interesting I think ill look upon this

  2. burned in MI
    burned in MI says:

    This just happened to me today at work! Heated up a mug for tea, noticed it wasn’t boiling and boom- right up the left side of my neck and face. About 2 tbsp of water left in the mug. True! Stopping for aloe vera on the way home.

  3. rishaad
    rishaad says:

    dont know if its true..but will find out …is microwave a health risk? i always use it to make tea..but lookin at u.s.a where baby boomers and society has grown up on microwave food, i dont see them affected now in life..those who used it in the 1980’s in usa japan etc..so doubt tht my mom is correct in saying microwave heating is bad for you, with the radiation etc..

    • Geeg
      Geeg says:

      It’s true! I just did it and am looking up whst to do, I am very fortunate that I only burned my right palm and thumbe and between my pointer and middle finger
      It’s begins to be very painful and I think I should head to the ER
      It was very shocking and like a volcano and it was only a 1/4 cup of water in a one cup measuring cup. (Not a new cup )
      Please be careful!!!

      Be careful

  4. Steve
    Steve says:

    Not sure about microwave ovens posing any health risks. I’m sure there’s plenty of stuff on the internet on both sides. Sorry I don’t know more about it.

  5. Mark in Everett
    Mark in Everett says:

    This is absolutely true! I have seen it happen. I have also had it happen to me. The first time it happened, it wasn’t water… it was soup. Bell went off, microwave stopped running. Opened the door, grabbed a napkin and some crackers, spoon. Then reached in to grab the soup, touched the little handle of the edge of the cup and blam, with 10 or 11 other employees watching, the soup shot straight up, covered the entire inside of the microwave, flooded out the front. Second time was just water in prep for ramen noodles. Same thing, touched it and sploosh, boiling water everywhere… burned me and actually shot out of the oven onto my shirt, pants and shoes.

    Believe it or you’ll likely pay a price for ignorance.

  6. ConnieJOS
    ConnieJOS says:

    I’ve had this happen. Scared me to death! I’d never heard of it before. I wanted to boil a cup of water, and I set the timer for 2 minutes. At the end, it hadn’t boiled at all, so I added more time. It still didn’t boil. I was looking through the window on the door to see if it was boiling, and all of a sudden… BOOM! It was enough force to fling the microwave door open. The cup jumped up and hit the top of the microwave, the sat back down straight up. It never turned over, but it was empty. All of the water shot out violently inside the microwave, and much of it sprayed out through the open door. I’d never seen anything like this before! That’s why I came to the internet to search to find out why this happened. Apparently, it’s fairly common! BE CAREFUL!!!

    • Howard
      Howard says:

      The same thing happened to me!The microwave no longer works. I was concerned about leaking radiation. Do you know if it’s possible that radiation could have leaked out from the microwave because of this explosion?

  7. Anonymous
    Anonymous says:

    Interesting phenomenon…it works with eggs too as I found out! Wanna try, take a styrofoam cup, crack an uncooked egg into it, discard the shell, microwave on high for 1 minute…in approx 45 seconds, your microwave will be goo-ed with half cooked egg matter…enjoy!

  8. Diana
    Diana says:

    This just happened to me. I put 8oz of water into a pyrex glass microwaveable jug and I heated it for about 3 minutes. When I opened the microwave to remove the water I noticed it was not boiling. I didn’t think much of it, so I reached in and picked up the jug by the handle. The water exploded out of the jug and scalded my arm. I never knew this could happen. I have now learned from reading in the internet to put a wooden spoon in the water to prevent this from happening.

  9. Steve
    Steve says:

    Diana — I going to have Dr. Gordon Linberg who is a burn specialist on as a guest on 9NEWS on Monday to discuss this very issue. I’ll be sure to post the streaming video on the blog.

  10. Gordon Lindberg, MD, PhD
    Gordon Lindberg, MD, PhD says:

    This is a real problem. The American Burn Association (ABA) has identified scald burns from superheated liquids in microwaves as a target for a new public awareness campaign. These burns are dramatic and traumatic because they often affect the face and hands of the burn victim. Fortunately, these burns rarely need grafting; however, they are extremely painful and in children these burns often lead to hospitalization for wound care and pain control. The best way to avoid these burns is to place a wooden coffee stirrer in the liquid when heating it and also to let all heated liquids cool for a few minutes inside the microwave before removing them.

    If you receive one of these burns, and especially if it covers the face or hands, seek a burn care specialist for care. Initial treatment for the burn can be performed in an ED or at a doctor’s office, but a burn specialist should see the burn within 24-48 hours after the injury, especially if the face is involved. If the eyes are involved, an ophthalmologist should be consulted immediately. Both burn units in the state of Colorado are open 24 hours a day/ 7 days a week/ 365 days a year. There is one in Greeley, CO and one at the University of Colorado in Denver.

  11. pittr
    pittr says:

    This is not an “urban myth”. It’s real and it’s painful. My son-in-law had to go every day to get his wound cleaned and rebandaged, then every other day.
    We took a picture of the burns on his hand right after it happened. I posted it on my blog, feel free to check it out. Not pretty!

  12. Chemist
    Chemist says:

    This phenomenon is not merely confined to the microwave but it could also happen on the stovetop or whenever you are heating a very pure liquid up.
    Tips: Avoid heating up either distilled or de-ionized water. These types of water have less ionic content than normal tap water. If your dish can stand it, put some salt in before boiling, this will increase the ionic content of the water and make it less likely to superheat.

  13. Beek
    Beek says:

    I’ve never heard of this before, but why can’t people just not super-heat their water? Why does tea or coffee or soup have to be SO hot?

  14. elizabeth doyle
    elizabeth doyle says:

    my daughter was making a poached egg in the microwave today when she took it out it blow p on her face she has blisters and her two eyes are burned we are just going up to the hostpital. she is in so much pain.

  15. Ron
    Ron says:

    This happened to me at work this morning. I had already heated a cup (not new) of water but forgot about it. When I finally went back to the microwave I had to reheat the water as it was only warm and not hot enough for my tea. I set the microwave for two minutes and was watching the cup so I could stop the microwave when I saw the water start to boil. At about one minute of time the water exploded out of the cup. I had never seen anything like this happen before and I have been boiling water in this manner for years.

  16. Mike
    Mike says:

    My son stuck a hard-boiled egg into the microwave to heat it up, and the egg exploded. Thing is, the microwave itself blew a fuse or something and there’s no power now. There’s no reset button, or anything. Anyone have any ideas?

    Thanks, if you do.


  17. Mike
    Mike says:

    My son put a hard boiled egg into the microwave to heat it up (no shell). The egg exploded with a terrific bang. Now the microwave has no power. There isn’t a reset key or anything. Any suggestions? Thanks in advance.

  18. Mark Nichols
    Mark Nichols says:

    I have also had this happen to me but not with water. I was heating up milk to make creamy cocoa. I was standing there waiting for the bubbles to start so that I would know when the milk was hot enough to add the chocolate powder into it. It never did boil so I opened up the microwave to see if it was hot enough by stirring the milk using a metal spoon. I guess the milk had formed a skin on top that did not let the heat escape and when I stuck the spoon into the milk it shot straight up out of the mug onto my hand and the inside top of the microwave and down onto the turntable. It scared me to death but fortunately it only burned a couple fingers and that’s all. I have never heated milk up in the microwave since.

    • Deborah
      Deborah says:

      this happened to me this morning, put a cup of milk in, but it didnt boil, so i gave it a bit longer, when i took it out it looked like the milk had seperated, i put a spoon in to stir it but it just exploded in my face.. quick reactions was to put cold water on the burns, got a couple of small blisters, but i guess it could of been a lot worse..! wont be doing that again..

  19. George Ealovega
    George Ealovega says:

    For anyone who thinks this cannot happen, my wife is presently at an Eye Surgery center with her mother. Her mother was removing a cup of microwaved water behind me in the kitchen, when the cup exploded, leaving steaming water and embedded shards of glass in the ceiling and walls. My wife just called from the hospital to say that her mother has lost her right eye totally to the flying glass and scalding water and her left has but a minor chance of recovering from the scalding should a cornea transplant become feasable sometime in the future.

  20. Brenda
    Brenda says:

    This happened to my father on the weekend, but with milk! He put his mug in the microwave with cold milk, like he has done for a long time. He saw it starting to bubble so stopped the microwave, reached in and took it out and as he did it exploded, scalding his forehead and a little into the scalp!
    The mug was still in tact and my father is currently in seeking medical assistance for his burns.
    Yes, indeed it does happen and not just with water!

  21. Just smiles
    Just smiles says:

    I was boiling and egg this past week and decided to use my microwave to do so. I cracked the shell and made a small hole so the egg would cook completely. Well when I went to take the egg out I saw that a soft spot in the egg was kind of pulsating. Now I figured this was just because water had actually gotten into my egg. So I took the tip of a knife with the plan to poke the spot and let out the water. The egg was still in the water i had boiled it in. Before I could think twice the tip of the blade touched the egg and it blew up in my face. I now have first degree burns on the right side of my face as well as second and first degree burns on my right hand and upper and lower right torso. Just an FYI for those who still think if you crack the shell after its started to boil to release the build up thats a LIE!!! Please note even though the microwave company’s have yet to have the warnings placed hard boiled eggs don’t get made in it. EVER!!!

  22. Robbyn
    Robbyn says:

    This just happened to us over Christmas !! We filled 1 cup of water in a 2 cup (glass) container. The glass container was not new. The water did not boil, so we started it again for 30 more seconds. The water exploded, still in the microwave, blew the door wide open , and water was everywhere in the kitchen. Could have been a very dangerous experience for us. We learned a great lesson.

  23. Femanon
    Femanon says:

    Water just exploded in my microwave..
    I had water in there and boiled it just fine, and while it was heating, I went back to my room and forgot about it.. I came into the kitchen a few HOURS later, noticed the water in there.. Picked up the cup, swirled it around a bit, and put it back in for the usual time.. I go back to preparing the thing that needed the water when I heard a BOOM. Before I turned around, I already knew what had happened. My water’s exploded before after heating a second time. I just figured that it was over heated.. This time, since it was there for HOURS, I didn’t think it would happen again. Well, it did. So I came to the internet in search for an answer.

  24. RuthK
    RuthK says:

    This just happened to me. I was microwaving water (filtered) in a Pyrex measuring cup to make couscous. It hadn’t boiled in the time I expected it to so I set the microwave for another 20 seconds. It still hadn’t boiled, but I figured it must be hot enough so I took out the cup and poured the couscous in. Immediately it exploded: boiling water and couscous scattered all over the kitchen and all over me, hardly any was left in the cup. Thankfully I had my glasses on; the boiling water spattered against my glasses. I received minor burns to my hands. I won’t be trying to boil just plain water in the microwave anymore — will either add some salt or a wooden stirrer to it.

  25. Sid
    Sid says:

    Hi steve, i was curious if you knew what it was that caused DI water to explode. It was brought up in a safety training video but that video is out of date. I work in a laboratory and was curious how someone figured that out. I want to say it had to do with cleaner or fire extinguishers, but i can’t recall.

  26. Curt
    Curt says:

    I had a similar but different experience with this. I was swapping out an old microwave with a new one. As a cleaning trick I learned, I put a corelle bowl filled with water to boil it to steam the insides of the microwave for easier cleaning. It worked fine, I saw the water boiling after about 2 minutes when I stopped the timer, took the bowl out and cleaned up the old microwave with ease.

    Next, after swapping out the old microwave with the new one, I put the same bowl with the same water (which was now cold) in the new microwave to clean it too. In less than a minute the water exploded inside the microwave while it was still running. I was worried that I had a defective microwave before reading this site.

    Apparently the first boiling made the water less able to release its vapor the 2nd time around.

  27. pablo
    pablo says:

    I have been looking for un answer after my incident with boiling water in a Pyrex cup.It is really dangerous to boil water in a microwave. I just boiled water as usual and for the first time the water in the cup exploded to the point that opened the microwave door and it almost hit me. Lucky I was by myself at the kitchen.

  28. Pete
    Pete says:

    Wow! isn’t it amazing how many people have experienced exploding water since this phenomenon was posted.

    Guess what, just this very morning, my microwave oven started vibrating when I had radio one on and it wasn’t even switched on.

    And only 30 minutes ago, I heard music coming from it.

    Has anyone got any idea what’s happening?

  29. Lee@Butter Keeper
    [email protected] Keeper says:

    I just had this happen to me a few minutes ago. I was microwaving a cup of water for coffee in a just-washed glass and it exploded on me when I tried to take it out. Luckily, the water only left light burns on my arms. Now I know what causes this and I’ll make sure to pay attention next time!

  30. Wanda
    Wanda says:

    This happened to me last night. I have boiled water alot in the microwave thousands of times. I used a white corningware container. I usually use a glass container, like a measuring cup. I was going to make some tea. It didn’t even boil, but was hot enough, but took it out anyway, turned around and boom. It burned my neck, chest area, under my chin, around my lip area, on right side of my eye. I wear glasses and water was all over my glasses, but one drop must of gotten in my right eye, cause it was bothersome through the night. I used aloe vera cream with a pain pill and it helped. This morning it feels like a sunburn, but no blistering. Thank God. I will be using a tea kettle from now on.

  31. sharon
    sharon says:

    this happened to me Saturday night. I was heating up water in a pyrex measuring cup (not new). The water didn’t boil. When I opened the door of the microwave, it exploded, hitting me on the right side of my face/forehead and left shoulder. I immediately wrapped ice cubes in a dampened baby soft washcloth and started dabbing my face. My face didn’t blister; however, the water that went through two layers of clothing (fleece and knit) made a blister on the top of my shoulder. It was a miracle that I didn’t suffer more severe burns, which I credit to the application of those ice cubes!

  32. James
    James says:

    A dangerous yet amazing phenomenum
    Just a hunch, but I suspect the not-new cups had been washed in the dish-washer, making them very clean (very low contaminent levels)and the water may have been filtered (or milk very low fat).

    Perhaps people can confirm this?

    Strange how this is most common for thos who heast the liquid for a second time (in one case with hours between).

    Surely either the energy of the erruption could be harnessed (on a larger scale) or the ability to produce and contain superheated water without high pressure can be exploited by the power industry??

    Quick – Run to the patent office!! 😉

  33. codestriker
    codestriker says:

    Just this morning i had this happen to me. so i was putting the water i use for my oatmeal. same old flow. when i microwaved it the first time it bubbled,then stopped. i took it out and drained the water. i refilled the measuring cup and put it back in. so i microwaved it AGAIN for six minutes. it was not doing any thing. HOWEVER, when it was three minutes into it the water suddenly spontaneously evaporated and the microwave door slammed open. scalding hot water got ALL over the place. i got a little burn mark on my hand. i cleaned it up and i did not have any breakfast,sadly 🙁 and get this: my dad blames i put something in the water to make it do that. i did not. i don’t get it. i always put in water in the microwave for six minutes. i don’t see why it would do that now. gosh, i am ticked off at my dad for blaming me for what the microwave did!! ):< I used the measuring cup a hundred times for this purpose and it NEVER DID THIS BEFORE!!!!

  34. Noel Bernal
    Noel Bernal says:

    I just had this very thing occur. I put tap water in a Pyrex cup with a tiny bit of lemon juice to steam it clean. I noticed the water wasn’t boiling after 5 minutes. I pulled it out, swabbed the inside of the microwave and decided to put the hot water back in to further steam the box. I added 3 minutes, walked away. After about a minute, I heard a very loud boom and instantly knew what happened…the Pyrex cup and the glass turntable remained intact, but the interior light will no longer turn off and the microwave stopped working. I assume the electronic parts got steamed & I’m hoping it’ll work after it dries out. The control panel looks normal. So much for this being a “rare” event, lol…

  35. Dave
    Dave says:

    I heat water all of the time, never had a problem. Only for 1 minute for a coffee mug full of water. Makes it too hot to drink, but hot enough to add cocoa or tea bags. Seems to me the problem might be the 5 or 6 minute settings being used, as well as the second heating.

  36. Hernan Vicuna
    Hernan Vicuna says:

    This just happened to me. I am in a lot of pain so I’m here to share my experience in hopes that it won’t happen to anyone else. Unfortunately, no one looks stuff like this up until it happens.

    Was heating about a cup of coffee, with creamer in it, in a smooth microwave safe Google travel mug. The setting on the Whirlpool microwave I used was “Reheat”. It goes for about 1.5 minutes and is set for 1 cup.

    I pulled the mug out dipped a spoon in to taste and it exploded all over me. I threw the mug but I got scalding coffee over both my hands. Hurts like hell. It was more of a very fast bubbling up and much like a volcano effect from what I can recall. I also rare that this is extremely “rare” – I would not count on that. I put an average amount of liquid, in an average mug for a preset time. I.e. this can happen to anyone.

    Hope this helps someone down the line…


  37. Stunned
    Stunned says:

    I also just had this happen, placed half a cup of pre-boiled water into our new microwave to steam clean it and 60sec into the two minute heat, no steam which I thought odd then BOOM the cup jumped up and most of the water blew out all over the inside of the microwave, thankfully the door stayed closed, I was standing about 1.5 meters away as I always do when the microwave is in use (I was advised to do this by a friend who understands this tech and works with microwave technology for safety reasons)
    anyway the microwave was still going so I walked over to stop it, I wasn’t sure why this just happened & a bit stunned so opened the microwave door but I should have pressed the cancel/stop button instead! I didn’t get scalded but water was everywhere & ran out onto the cupboard with only a little left in the cup. After I felt a mild uncomfortable warm feeling in the middle of my chest & a lump in my throat with some excess swallowing & is still present over half an hour later!
    Common sense tells me that sensation is most likely globbis hystericus and reflux mixed with a bit of adrenalin caused by the BOOM but wondering if anyone who may read this with technical industry knowledge would know if it would be possible to have been hit in the chest with active microwave waves when the door was opened as the microwave is chest height! I am now convinced our new inverter microwave is evil as our old one never did this so I will be taking it back to the shop for a refund 😉 lol

  38. deb
    deb says:

    Well add me to list. Was heating cup of water with lemon to clean microwave. I had heat water 3 minutes
    but forgot about it and oven had dried. Put cup in for another 3 minutes. I had my back to it but door of oven exploded open. Cup had only maybe one once left. By the way the oven had 36 seconds left on time.

  39. CK
    CK says:

    WOW! NEVER knew this could happen?? I have boiled h2o many times, this never occurred……..until yesterday!! Thank God I wasn’t standing 6 in. closer or I would have surely sustained blunt force trauma to the face! It seemed VERY forceful! Scared the @%#* out of me! Dangerous. I will be spreading this news!


Trackbacks & Pingbacks

  1. […] exploded in a blast of boiling water. It scalded my arm quite badly. This does happen, see here and here Better yet of course use a teapot or different container to boil your water. Now back to your […]

  2. […] Steve Spangler gives one of the simplest yet most informative descriptions on his blog. Comments left by people show that this is not a unique occurrence. […]

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