The Danger of Micro-Waving Water

The Danger of Micro-Waving Water

A 26-year old man 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.., (nothing 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 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 our local science teacher had to say:
   
     '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.'
    
      If you pass this on you could very well save
      someone from a lot of pain and suffering.