The following is from my internal Boeing web site concerning such matters.
Basically, it extremely simple to recognize a legend, hoax, chain letter,
exageration, etc. If it says pass it on or some such statement, I don't!!!
Simple as that!

Do you honestly think if something like this could happen as easily as
inferred, that there would not be warnings plastered all over the microwave
literature?

Darwin

_ - - - - - - - -

Microwave warning about boiling water - Chain Letter (1/21/00)

                                 The underlying premise that water
superheated in a microwave could 'explode' is within the
                                 realm of scientific possibility. The
incident described cannot be verified, so the story is
                                 unreliable. The contention that this is a
common occurrence is inaccurate. This topic may be
                                 appropriate for a safety meeting, but from
a resource use perspective, it is not appropriate
                                 to use company e-mail to send it out, at
least not in its current 'scare-o-gram', chain letter
                                 form.

                                 In an article at

http://urbanlegends.about.com/culture/urbanlegends/library/weekly/mcurrent.h
tm it says:

                                      "First, let's consider the story
itself. Is it word-for-word true? Unfortunately, we
                                      have no way of knowing. The author is
anonymous, the victim is anonymous,
                                      we are not told where or exactly when
it happened. It's unverifiable."

                                 And -

                                      "[W]e know it's possible. But is it
common? Not very, says Louis Bloomfield,
                                      professor of physics at the University
of Virginia. "Fortunately, serious
                                      microwave superheating accidents are
unusual - this is the first injury I've ever
                                      heard about." This contradicts the
email's claim that it's a "fairly common
                                      occurrence." A search of the medical
literature on microwave injuries also failed
                                      to support that claim. There are
references to trauma caused by everything
                                      from overheated pizza to exploding
eggs, but no mentions I could find of
                                      serious injury due to surges or
explosions of boiling water."

                                 Since the warning urges the recipient to,
"Please pass this information on to friends and
                                 family.", it's technically a chain letter.
Administrative policy PRO-10 Proper Use of Company,
                                 Customer, and Supplier Resources says,
"E-mail may not be used for external broadcast
                                 messages or to send or post chain letters"

                                      Subject: Safty Alert - Microwaving
Water

                                      This report was just passed to me by a
safety manager who thought people should be
                                      aware of the following information in
case they use a microwave oven to heat water:

                                      About five days ago my 26-year old son
decided to have a cup of instant 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; but he told me
                                      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 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 flew out onto his face
due to the buildup 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 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. Please pass this information on to
                                      friends and family.


> ----------
> From:         Kelly Grant[SMTP:[log in to unmask]]
> Sent:         Tuesday, September 12, 2000 9:50 AM
> Subject:      NON PD - Micro wave caution
>
> This is a "forward" item I received. I don't know whether or not this is a
> hoax but I decided to err on the side of caution and forward to you.
>
> -------------------------------------------------------
>
> Warning...... HEATING WATER IN MICROWAVE
>
> The following information is important for anyone using a microwave oven
> to
> heat water. This information should be a topic of discussion at work or at
> home.
>
> Recap of a recent real event:
>
> "About two weeks ago, my 26 year old son decided to have a cup of instant
> coffee. He took a cup of water and put it in the microwave to heat it up
> (something he has done numerous times before).  I'm not sure how long he
> set
> the timer for, but he told me he wanted to bring the water to a boil. When
> the oven timer shut off, he removed  the cup from the oven.
>
> As he looked into the cup he noticed the water was not boiling but
> instantly
> the water in the cup "blew up" in 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 with possible scarring.  He also may lose
> partial sight in his left eye.
>
> While at the hospital, the attending doctor stated this 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, like a wooden stir stick, tea bag, etc. It is a much
> safer choice to boil the water in a kettle on the stove top.
>
> Here is what our science teacher had to say on the matter:  "Thanks for
> the
> microwave warning.  I have seen this happen before. It's caused by a
> phenomenon known as 'super heating'. It can happen any time water is
> heated
> and will particularly occur if the vessel the water is heated in is new.
>
> What happens is 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 provide a place for the bubbles to form.  When 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 usually happens then is 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."
>
> Please pass this information on to family and friends. It could save a lot
> of
> pain and suffering.
>