[Phys-L] Re: tiny bubbles

[Bernard Cleyet <bernardcleyet@REDSHIFT.COM>]

I've posted this before.  Chemist's call it "bumping", and add a boiling
bead to prevent.  Note either don't reuse or wash and allow to dry
before reuse.  One may make their own by taking a hammer to a discarded
globar.  That's the SiC rod used in most toaster ovens.   I guess these
are boiling chips and the beads are rough surface glass.

After (re)reading Beatty's discussion, I read the first linked article
on CD's (I'm going to try w/ DVD for any diff.)  I was pleased to find
that author agrees w/ my interpretation of the cause.  Not spark
discharge from high field that breaks down the air, but instead a plasma
discharge due to the vaporization of the Al.  I came to this conclusion,
because of the long delay before the effect, when I used a low power
oven along w/ absorption by glasses of water.  Also the Al film is
continuous w/ undulations not concentric rings necessary to produce the
high fields for the other theory.

bc

Scott Goelzer wrote:

> Water boiled in a microwave can do something like this.
>
> good writeup at:
> <http://amasci.com/weird/microwave/voltage2.html#coffee>
>
> I've seen it happen personally - it's scary.
>
> Scott
>
>
> On Feb 10, 2006, at 4:09 PM, Anthony Lapinski wrote:
>
>
>
> > I know that champagne bubbles form at imperfections in the glass,
> > and then
> > rise up from these "nucleation sites." Similarly, when boiling
> > water in a
> > beaker, the bubbles form on the glass bottom at the imperfections.
> > Students were wondering what would happen if the glass were "perfect."
> > Where would the bubbles begin to form? I assume more bubbles would
> > form
> > (uniformly) in the deepest part of the liquid (champagne or boiling
> > water), but I don't know for sure. Can anyone support or refute this?
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