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Microwaving Water Dangerous!


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60 replies to this topic

#1 of 61 OFFLINE   Audioman321

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Posted March 24 2009 - 07:44 PM

Is this true? (March 2009)

From a friend:

This is true - I checked with Snopes.

Safety Warning

Microwaving Water!

A 26-year old man decided to have a cup of coffee. He took a cup of water and put it in the microwave to heat it up (something that he had done numerous times before). I am not sure how long he set the timer for, but he wanted to bring the water to a boil. When the timer shut the oven off, he removed the cup from the oven. As he looked into the cup, he noted that the! water was not boiling, but suddenly the water in the cup 'blew up' into his face. The cup remained intact until he threw it out of his hand, but all the water had flown out into his face due to the build up of energy. His whole face is blistered and he has 1st and 2nd degree burns to his face which may leave scarring.


He also may have lost partial sight in his left eye. While at the hospital, the doctor who was attending to him stated that this is a fairly common occurrence and water (alone) should never be heated in a microwave oven. If water is heated in this manner, something should be placed in the cup to diffuse the energy such as a wooden stir stick, tea bag, etc.., (nothing metal).


General Electric's Response:


Thanks for contacting us, I will be happy to assist you. The e-mail that you received is correct. Microwaved water and other liquids do not always bubble when they reach the boiling point. They can actually get superheated and not bubble at all. The superheated liquid will bubble up out of the cup when it is moved or when something like a spoon or tea bag is put into it.


To prevent this from happening and causing injury, do not heat any liquid for more than two minutes per cup. After heating, let the cup stand in the microwave for thirty seconds! before moving it or adding anything into it.


Here is what our local science teacher had to say on the matter: 'Thanks for the microwave warning. I have seen this happen before. It is caused by a phenomenon known as super heating. It can occur anytime water is heated and will particularly occur if the vessel that the water is heated in is new, or when heating a small amount of water (less than half a cup).


What happens is that the water heats faster than the vapour bubbles can form. If the cup is very new then it is unlikely to have small surface scratches inside it that provide a place for the bubbles to form. As the bubbles cannot form and release some of the heat has built up, the liquid does not boil, and the liquid continues to heat up well past its boiling point.


What then usually happens is that the liquid is bumped or jarred, which is just enough of a shock to cause the bubbles to rapidly form and expel the hot liquid. The rapid formation of bubbles is also why a carbonated beverage spews when opened after having been shaken.'

#2 of 61 OFFLINE   drobbins

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Posted March 24 2009 - 11:09 PM

Snopes does confirm it, but I don't see how this could be true. Water changes from a liquid to a gas at 212F at standard atmospheric pressure. The only way I know of to have liquid water at a higher temperature is if it is pressurized. Also, microwave ovens have been out 30(?) years now. If this was true, it would be common knowledge. Either that or everyone is using dirty dishes.

#3 of 61 OFFLINE   Jerry Almeida

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Posted March 24 2009 - 11:34 PM

Well, to be honest, I thought it was common knowledge.
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#4 of 61 OFFLINE   mattCR

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Posted March 25 2009 - 12:15 AM

In order for this to happen, though, the water has to be damn near pure with almost no contaminants. So, for the most part, it doesn't happen. Keep heating and heating distilled water, though, and you can produce this effect.

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#5 of 61 OFFLINE   Jeff Gatie

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Posted March 25 2009 - 12:48 AM

I've seen it with my own eyes. Didn't get scalded, but a cup of tea boiled over as soon as the bag hit the surface.

Alton brown uses a chopstick in the container to prevent this, and we all know Alton Brown is a god.



By the way, that's what the guy gets for drinking instant coffee. Blech!!

#6 of 61 OFFLINE   Jeff Gatie

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Posted March 25 2009 - 01:00 AM

Quote:
Originally Posted by drobbins
Snopes does confirm it, but I don't see how this could be true. Water changes from a liquid to a gas at 212F at standard atmospheric pressure. The only way I know of to have liquid water at a higher temperature is if it is pressurized. Also, microwave ovens have been out 30(?) years now. If this was true, it would be common knowledge. Either that or everyone is using dirty dishes.

It has to do with the temperature of the water vs. the temperature of the container, and imperfections in the surface of the container. In order for water to boil, there has to be a process called "nucleation", where microscopic bubbles of steam gather together to form bigger bubbles. If you are boiling in a kettle, nucleation usually happens at the sides and bottom of the kettle, where a greater temperature exists (due to an exterior heat source) and small imperfections in the surface of the heated kettle (usually metal) are a breeding ground for microscopic steam bubbles, due to more contact surface area around these imperfections. These imperfections can also contain tiny trapped air bubbles, which can start the nucleation process as well.

But in a microwave, the water heats much faster than the container. This disparity of heat in the container vs. the water, coupled with a smooth surfaced container (usually glass or ceramic), are not a very good breeding ground for the microscopic bubbles needed for nucleation. No tiny bubbles, no big bubbles. No big bubbles, no boil . . . no matter how hot the water gets.

#7 of 61 OFFLINE   Steve_Pannell

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Posted March 25 2009 - 01:40 AM

Quote:
Originally Posted by Jeff Gatie
I've seen it with my own eyes. Didn't get scalded, but a cup of tea boiled over as soon as the bag hit the surface.


I had this happen with instant hot chocolate once. As soon as I dropped the spoon of powder into the cup it erupted. Made a big mess. I make sure now that I slowly ease the spoon into the hot water.

#8 of 61 OFFLINE   brandonchenry

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Posted March 25 2009 - 01:48 AM

wow guys. i love learning something new. good way to start the day.

#9 of 61 OFFLINE   Dennis Nicholls

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Posted March 25 2009 - 03:11 AM

It goes the other direction too. You can have supercooled water which instantly turns into ice upon shaking. I've seen this here in Boise: put a plastic water bottle onto the patio table over a freezing night. In the morning, the water in the bottle will still be liquid until you pick it up. It will then almost instantly transform into the solid state while you are holding it. Looks like some strange special effect.

Wouldn't the superheating effect be mitigated by the motion of a turntable in a modern microwave oven? Posted Image Did the flash boiling described above only occur in a cheap microwave without turntable?
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#10 of 61 OFFLINE   Matt^Brown

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Posted March 25 2009 - 03:57 AM

I like to think that I know things but I have been educated this morning. I understand the concept but I have never thought about it to the point of explaining the potential hazard to my kids. I guess I have some teaching to do tonight.
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#11 of 61 OFFLINE   nolesrule

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Posted March 25 2009 - 03:59 AM

Quote:
Originally Posted by Dennis Nicholls
Wouldn't the superheating effect be mitigated by the motion of a turntable in a modern microwave oven? Posted Image Did the flash boiling described above only occur in a cheap microwave without turntable?

The answer to that is no. Have you ever had a liquid in a bowl or glass with a spec of something in it, but when you rotate the container, the spec stays in the same place?

I have a Panasonic microwave with turntable and when I forget to use the Alton Brown chopstick trick, the superheating will always occur. No one has ever been injured, but adding a tea bag will cause a large fizz up.

We use filtered water for our cooking because it tastes better. But the superheating is more likely to occur because of this.

#12 of 61 OFFLINE   Kirk Gunn

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Posted March 25 2009 - 04:22 AM

Interesting stuff... I had heard of superheating, but thought it was extremely rare (also thought Alton was merely impressing everyone with his knowledge of arcane cooking theory).

Didn't know it was so common an occurrence and can be readily reproduced....

#13 of 61 OFFLINE   Jeff Gatie

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Posted March 25 2009 - 04:32 AM

Quote:
Originally Posted by Kirk Gunn
(also thought Alton was merely impressing everyone with his knowledge of arcane cooking theory).


Alton does this without trying. The man once dried a salmon on a hotel room air conditioner, then smoked it in a cardboard box.

#14 of 61 OFFLINE   Carlo Medina

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Posted March 25 2009 - 04:36 AM

This is one "urban legend" which is true, and the scientific explanation in the OP is correct. I have experienced it myself. Now I have bought a water boiler/heater to keep water hot for coffee/tea rather than using the microwave.

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#15 of 61 OFFLINE   Radioman970

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Posted March 25 2009 - 05:10 AM

As long as my coffee doesn't do this. I pre-make coffee in the coffee maker, keep it in a pitcher in the frig and heat me a cup in the morning. If I'm going to get hot coffee in my face I want it to be because I pinched a waitress.
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#16 of 61 OFFLINE   drobbins

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Posted March 25 2009 - 05:22 AM

Quote:
Originally Posted by Jeff Gatie
It has to do with the temperature of the water vs. the temperature of the container, and imperfections in the surface of the container. In order for water to boil, there has to be a process called "nucleation", where microscopic bubbles of steam gather together to form bigger bubbles. If you are boiling in a kettle, nucleation usually happens at the sides and bottom of the kettle, where a greater temperature exists (due to an exterior heat source) and small imperfections in the surface of the heated kettle (usually metal) are a breeding ground for microscopic steam bubbles, due to more contact surface area around these imperfections. These imperfections can also contain tiny trapped air bubbles, which can start the nucleation process as well.

But in a microwave, the water heats much faster than the container. This disparity of heat in the container vs. the water, coupled with a smooth surfaced container (usually glass or ceramic), are not a very good breeding ground for the microscopic bubbles needed for nucleation. No tiny bubbles, no big bubbles. No big bubbles, no boil . . . no matter how hot the water gets.
Well I guess I know what I am doing tonight - playing with the microwave.

#17 of 61 OFFLINE   Jeff Gatie

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Posted March 25 2009 - 07:42 AM

Quote:
Originally Posted by drobbins
Well I guess I know what I am doing tonight - playing with the microwave.

Don't do it. Seriously. Depending on how much you heat it (and no one can really say how much is "too much"), it really can explode in your face and cause serious injuries; burns, scarring, even blindness. There are enough videos on the net if you really want to see the effects.

#18 of 61 OFFLINE   Steve_Pannell

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Posted March 25 2009 - 07:47 AM

Quote:
Originally Posted by Jeff Gatie
Don't do it. Seriously. Depending on how much you heat it (and no one can really say how much is "too much"), it really can explode in your face and cause serious injuries; burns, scarring, even blindness. There are enough videos on the net if you really want to see the effects.

And you don't know when it's going to happen. It might happen when you pick it up instead of dropping in a teabag or spoon of coffee or whatever.

A tube of Mentos dropped in a 2 liter bottle of Diet Coke is safer and more impressive. Posted Image

#19 of 61 OFFLINE   Bryan X

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Posted March 25 2009 - 08:32 AM

I had this happen to me once too. Boiled a cup of water in the microwave, and as soon as I put a spoon in the water, it erupted. Scared the shit out of me.

#20 of 61 OFFLINE   Holadem

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Posted March 25 2009 - 08:40 AM

Quote:
Originally Posted by Jerry Almeida
Well, to be honest, I thought it was common knowledge.
Meeee toooooooo.

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