THE DANGERS OF BOILING WATER IN A MICROWAVE OVEN
 
The following e-mail was sent to National Safety from one of our readers.
 
"I feel that the following information that anyone who uses a microwave oven
to heat water should know. My 26-year old son 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 that he wanted
to bring the water to boil. When the time shut the oven of, he removed the
cup from the oven. As he looked into the cup, he noted that the water in the
cup 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 a
fairly common occurrence and water (alone) should never be heated in the
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 water in a teakettle.
Please pass this information on to friends and family.
 
General Electric's Response:
 
"The e-mail that you received is correct. Microwaved water and other liquids
do not always bubble when they reach 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. I hope this helps. Should you need any
further assistance, please contact us.
 
Response from a Scientist
 
"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 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. The rapid formation of bubbles is also why a
carbonated beverage spews when opened after having been shaken".
 
 
If you pass this on you could very well save someone from a lot of pain and
suffering.