Re: superheated drink (was: How to explain this?)

["John S. Denker" <jsd@MONMOUTH.COM>]

Dan MacIsaac wrote:

> This is a real safety issue with liquids microwaved in ceramic
> containers.

Right!  Just about any containers, really.

I hope everybody is listening.  I don't care how many
instances of mild superheating you've seen.  You can
eventually by accident and fairly easily on purpose
create a high degree of superheating, and that can be
seriously dangerous.

There are proper procedures for experimenting with
explosives.  If you haven't been indoctrinated in the
proper procedures, don't rush in where angels fear to
tread.

Give your students the don't-try-this-at-home speech.

You can't win by avoiding the subject;  people need
to know about it, because it can happen inadvertently.

Specific advice:
 -- Be generally aware of the possibility.  Certainly
    be careful of anything that might be superheated.
    Don't hold it near yourself until you've added
    some good nucleation sites or otherwise verified
    that it's not going to blow up.
 -- Think twice before re-heating something that was
    left to sit after previous heating.  See archives
    for why.
 -- Don't heat something more than "ought" to be
    necessary based on its size et cetera.

> Superheated boiling has also been discussed extensively on PHYS-L;
> search the archives for "superheated".

Yes.

And I think this explains about 95% of Ludwik's
question.

The other 5% is that he reported seeing the liquid
"just start to rise".  That's odd.  Usually when I've
superheated stuff, there was no sign that it was
anywhere near boiling until it nucleated, and then
boom!  All or nothing.

To fully explain Ludwik's report, one has to imagine
that some of the liquid was superheated but some of
it wasn't.  This would depend on details, perhaps a
history of slight sloshing, or ....??????