My
family member closed to me 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.., (No metal).
General Electric's Response
Thanks for contacting us, I will be happy to assist you. The
e-mail that you received is correct. Micro waved water and other liquids do not
always bubble when they reach the boiling point. They can actually get super-heated and not bubble at all. The super-heated 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 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 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.
