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 1^st and 2^nd 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.