While at the hospital, the attending physician told the man that the circumstances surrounding how he had received his injuries were fairly common. How would you like to be told that such a common event could produce such serious injuries – on a regular basis?
What we found is that water (alone) should never be heated in a microwave oven. When water is heated in a microwave something should be placed in the cup to diffuse the energy – such as a wooden stir stick or even a tea bag – obviously, nothing metal should be used.
Here is how a major appliance manufacturer responded to the above event: “Thanks for contacting us, I will be happy to assist you. The information that you received [regarding the hazards surrounding heating water in a microwave] is correct.
“Microwaved water and other liquids do not always bubble when they reach their boiling point. They can actually become 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 placed therein.”
Here is what one expert had to say: “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 (less than half a cup).
“What happens is that the water heats faster than 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.
“When the container is bumped or jarred it can cause 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.”
To prevent water from exploding in a microwave:
• Do not heat any liquid for more than two minutes per cup.
• After heating, let the cup stand in the microwave for 30 seconds – before attempting to remove it or before attempting to add anything to it.
• Use a container whose interior surface is at least a little scratched.
• Tap the outside of the container a few times with a solid object while it is still in the oven. Use a long object so that your hand remains outside the oven.
• Keep your face well away from the open oven door and from the container.
All these precautions should reduce the chance or extent of superheating and resultant injury. Nevertheless, very hot water is always dangerous and one should always treat it with caution.
James Carey and Morris Carey are nationally recognized experts on home building and renovation.