From: share-unlimited@yahoogroups.com
Interesting... don't know its authenticity but it appeared in some posts...
''A 26-year old person 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
told me 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 instantly 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 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. It is however a much safer choice to boil
the water in a tea kettle.
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 a 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 vapor 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 that 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.
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