Molten lava in your microwave oven

[William J. Beaty]

I found a piece of red pumice on the top of the parking garage at the UW.
It's the kind you see in gas-powered barbecue grills, or used as decorative
stone spread under bushes, a little dusty red 2-in fragment full of bubbles.
I kept it because it's location was weird. (Seagulls took it up there?
Did it fall from the sky a la Charles Fort?)


Brainstorm! Last week I realized that pumice might be volcanic glass but
with so much outgassing that it forms a rigid foam and appears diffusive-
opaque instead of black/transparent. Since it's easy to melt quartz in
a microwave oven if it's full of ionic impurities (such as sodium or
boron, normal glass or Pyrex,) the pumice might be the same. When
liquid, glass is an electrolyte, a resistor, so it's strongly heated
by microwaves.

So I heated the top of the stone to slightly red heat with a plumber's
torch and stuck it in the microwave for a minute. (small 900 watt oven.)
It became red hot and also emitted lots of plasmoids from carbon crap on
its surface, but it did not melt visibly.

Today I futzed with it some more. I lifted it up on an overturned dish,
heated its top yellow-hot with a MAPP gas plumbing torch (much hotter than
propane), and nuked it for a minute. It just glowed dull red, but I
noticed that the entire ceramic dish was quite hot. Then I noticed that
the rotating glass platter was also hot. With no RF load, the standing
waves build up until any feeble absorber sucks up the oven's entire output.

I got rid of the dish and the glass platter, and placed the pumice
fragment on an inverted paper cup. I heated its top to yellow hot again,
slammed the door and hit start. It glowed, then darkened, so I moved the
cup over an inch to find a "hotspot." Repeat. It glowed, then darkened,
but this time there was some red glow peeking out from deep inside the
holes in the pumice. The glow increased and momentarily became
incandescent white (painful to look at.) Then the glow started spreading
through the stone, became orange, and finally a thin crust broke out of
the side of the block and a slow stream of bright yellow lava started
oozing forwards, carrying black crust fragments as it came. Something
right out of a nature program, but in miniature. I hit "stop" and it
halted immediately, but not before I... POKED IT WITH A STICK. It
never even burned the paper cup. When cool it looked like a glob of
shiny black glass.

Is that cool, or what!

INCANDESCENTLY cool.


Also prev thread:
I just MELTED a frikkn beer bottle
http://groups.google.com/groups?&th=580508e39f785852&[email protected]#link1


(((((((((((((((((( ( ( ( ( (O) ) ) ) ) )))))))))))))))))))
William J. Beaty http://staff.washington.edu/wbeaty/
[email protected] Research Engineer
http://amasci.com UW Chem Dept, Bagley Hall RM74
206-543-6195 Box 351700, Seattle, WA 98195-1700

 

[Carl 1 Lucky Texan]

There's a guy named Reid (IIRC) that casts metal in a m'wave. Uses a
ceramic slip with silicon carbide and magnetite mixed in to do a type of
Ashanti casting. Very interesting.

Carl
1 Lucky Texan

 

[Uncle Al]

I found a piece of red pumice on the top of the parking garage at the UW.
It's the kind you see in gas-powered barbecue grills, or used as decorative
stone spread under bushes, a little dusty red 2-in fragment full of bubbles.
I kept it because it's location was weird. (Seagulls took it up there? Did
it fall from the sky a la Charles Fort?)

[snip]

It's slag from an ironworks. They'll give it to you by the tonne for
free if you'll pick it up from the site.

 

[John Popelish]

I got rid of the dish and the glass platter, and placed the pumice
fragment on an inverted paper cup. I heated its top to yellow hot again,
slammed the door and hit start. It glowed, then darkened, so I moved the
cup over an inch to find a "hotspot." Repeat. It glowed, then darkened,
but this time there was some red glow peeking out from deep inside the
holes in the pumice. The glow increased and momentarily became
incandescent white (painful to look at.) Then the glow started spreading
through the stone, became orange, and finally a thin crust broke out of
the side of the block and a slow stream of bright yellow lava started
oozing forwards, carrying black crust fragments as it came. Something
right out of a nature program, but in miniature. I hit "stop" and it
halted immediately, but not before I... POKED IT WITH A STICK. It
never even burned the paper cup. When cool it looked like a glob of
shiny black glass.

Is that cool, or what!

INCANDESCENTLY cool.

Definitely!

These experiments are a race between energy absorption and energy
radiation, conduction and convection.

 

[Edward Green]

I found a piece of red pumice on the top of the parking garage at the UW.
It's the kind you see in gas-powered barbecue grills, or used as decorative
stone spread under bushes, a little dusty red 2-in fragment full of bubbles.
I kept it because it's location was weird. (Seagulls took it up there?
Did it fall from the sky a la Charles Fort?)

[snip]

It's slag from an ironworks. They'll give it to you by the tonne for
free if you'll pick it up from the site.

I once picked up a peculiar piece of black micro-porous glassy stuff
on the beach at Coney Island. After extensive consultation in the
geology group, I still wasn't able to figure out what it was, but I
thought it might be slag...

 

[Edward Green]

"William J. Beaty" wrote:

Hot stuff!

Definitely!

These experiments are a race between energy absorption and energy
radiation, conduction and convection.

Yes ... also evidence regarding the effective radiation temperature of
the microwave: those excited modes are pumped up beyond an equivalent
of white heat, since they are able to transfer energy up to those
temperatures.

The word "maser" isn't used much anymore... no, I guess microwave
ovens aren't masers -- the "stimulated emmision or radiation" part
implies some chemical medium?

 

[Ian Stirling]

The word "maser" isn't used much anymore... no, I guess microwave
ovens aren't masers -- the "stimulated emmision or radiation" part
implies some chemical medium?

MASERS are wierd, generally low-power beasts, using (IIRC) ammonia
in a near vacuum excited electrically to act as a lasing medium. (typically
used as an amplifier)
They have fallen out of favour recently for most applications as
semiconductors are much, much cheaper, smaller, and require less power
and volume/...

 

[Ian Stirling]

So far, so good. The next step must be to make a real working lava lamp.

Sapphire tubes can be obtained, though not cheaply.
I wonder if they'd work.

 

[William J. Beaty]

It's slag from an ironworks. They'll give it to you by the tonne for
free if you'll pick it up from the site.

Aha! That explains the rust-red color. I'm familiar with
pacific island pumice, and mediterranean pumice, but hadn't
seen any red stuff before.

(And to the other guy, no, it's not coral. I grew up in
Florida and Guam, I've seen all sorts of coral. This stuff
is volcanic, either from human-made lava flows (steelmaking)
or from natural ones.)

 

[William J. Beaty]

I once picked up a peculiar piece of black micro-porous glassy stuff
on the beach at Coney Island. After extensive consultation in the
geology group, I still wasn't able to figure out what it was, but I
thought it might be slag...

Grind up a bit of it and see if you smell sulfur. If
so, then it's similar to pacific volcano pumice. I wonder
if there's any natural pumice which DOESN'T contain
encapsulated HS gas.

 

[William J. Beaty]

These experiments are a race between energy absorption and energy
radiation, conduction and convection.

Just by chance the melt zone migrated into the middle of
the piece of rock. With a few mm of rock acting as a
barrier against heat loss (but not acting as a barrier
against microwaves) it quickly reached bright yellow
incandescence inside. If I try it many times I might
not be as lucky.

If the melt zone were to absorb the entire 900W oven output,
and if it remained surrounded by solid rock, I wonder how
hot it would become? I recall that the melting point for
quartz is also near its boiling point, so that would set
one limit.

 

[William J. Beaty]

So far, so good. The next step must be to make a real working lava lamp.

YES! If I used a huge rock, and could somehow trigger the melt
zone to form deep inside, wouldn't the fluid be less dense than
the surrounding material? It would eat its way upwards just
like a natural lava chamber, then break through at the top of
the stone. It might take hours or days. A home-built desktop
volcano. Or chose a wet piece of rock if you want a Krakatoa-
type effect?



Heyyyyyy. Here's a scam. I remember seeing large amounts of
Trinitite on eBay awhile back. A little bit of Utah desert sand,
a little bit of uranium chloride or powdered Torbernite, and a
few hundred watts of microwave? It would even end up with
little clingy bits of unmelted sand all over one side.

 

[Timo Nieminen]

but this time there was some red glow peeking out from deep inside the
holes in the pumice. The glow increased and momentarily became
incandescent white (painful to look at.) Then the glow started
spreading
through the stone, became orange, and finally a thin crust broke out
of
the side of the block and a slow stream of bright yellow lava started
oozing forwards, carrying black crust fragments as it came. Something
right out of a nature program, but in miniature.

So far, so good. The next step must be to make a real working lava lamp.

 

[Joseph.D.Warner]

MASERS are wierd, generally low-power beasts, using (IIRC) ammonia
in a near vacuum excited electrically to act as a lasing medium. (typically
used as an amplifier)
They have fallen out of favour recently for most applications as
semiconductors are much, much cheaper, smaller, and require less power
and volume/...

I don't know if masers are weird. NASA still uses ruby masers in our
deep space network; though we cool it down a bit.

 

[Joseph.D.Warner]

Sapphire tubes can be obtained, though not cheaply.
I wonder if they'd work.

If it is becoming brillantly white hot as opposed to white hot then I
think the sapphire tube will melt.

 

[William J. Beaty]

It's slag from an ironworks. They'll give it to you by the tonne for
free if you'll pick it up from the site.

I wonder if the foundry adds material to lower the melting point
of the ore? Real lava might not melt so easily. On the other
hand, films depicting flowing lava show a material that's only
orange or yellow-hot, not brilliant blue/white.

 

[Uncle Al]

I wonder if the foundry adds material to lower the melting point
of the ore? Real lava might not melt so easily. On the other
hand, films depicting flowing lava show a material that's only
orange or yellow-hot, not brilliant blue/white.

It isn't lava, it is slag. Do you know how to make raw iron? Ore,
coke, limestone; oxygen/heat. If there were any way to do it cheaper,
it would be done cheaper. Nobody gives a damn about anything except
cost until you have molten metal in the kettle. Blask a laser in
there, see what emits, adjust alloying elements by addition; sulfur
and phosphorus by reaction.

 

[Ian Stirling]

I don't know if masers are weird. NASA still uses ruby masers in our
deep space network; though we cool it down a bit.

I did say most applications.

You have to admit that the ruby MASER is not exactly widely used, though
it has its place. (in a liquid helium refrigerator usually)

(I'd forgotten about ruby based ones)

 

[Edward Green]

Grind up a bit of it and see if you smell sulfur. If
so, then it's similar to pacific volcano pumice. I wonder
if there's any natural pumice which DOESN'T contain
encapsulated HS gas.

Don't have anymore, but do recall it crackled on heating and on
scratching it it gave off a fine cloud of powder and faint smell of
sea -- not too surprising, since it washed up on the beach. Don't
recall sulfurous smell.

Also saw proverbial drowned rat: well, almost drowned. A trail led
out of the surf, and there, just above the limit of wave action, lay a
large rat, alive, but too exhausted to move when you approached him.
I wonder how far he had swam, and what ship he had jumped? An
Odysseus among rodents.

 

[Scott Stephens]

I found a piece of red pumice on the top of the parking garage at the
UW. ....
Since it's easy to melt quartz in
a microwave oven if it's full of ionic impurities (such as sodium or
boron, normal glass or Pyrex,) the pumice might be the same. When
liquid, glass is an electrolyte, a resistor, so it's strongly heated
by microwaves.

You ever try those pop-rocks or volcano candy that fizzes in your mouth?
Perhaps you can put something inside some glass frit that will cause it
to fizz and foam up while you zap it?

I once made a delightful glop out of battery acid (H2SO4) sodium
chlorate, a bit of powdered sulfur and, the magic pinch of catalyst,
sodium bisulfate.

Depending on the chemical concentrations, it would spark and sputter and
boil and emit noxious sulfur and chlorine, and ignite little fuses.
Truly charming. But it got really interesting when I took it out of the
dungeon and exposed it to sunlight!

Why not go for a lower temperature electrolyte using sodium carbonate or
hydroxide. Try some ammonium persulfate, permanganate or bisulfate to
get things interesting. Use some porous separator and a resonant copper
ring. Perhaps you can form a rectifier junction?

Or maybe checkout its thermo-acoustic properties. Familiar with singing
flames? Acoustic refrigeration? Rocket-pumped plasma-masers? Put some
reactive glop in a waveguide and see if you can eject plasma out, or
amplify the microwaves through the MHD action of the plasma!

I hear Military-grade rocket-pumped plasma maser death beams have
nothing to do with direct-current MHD effects, but rather use pulsed (or
superconducting) electromagnets around the plasma waveguide to cause
Langmuir oscillations or inverse Landau damping. They function more like
AC alternators than DC generators.

I hit "stop" and it
halted immediately, but not before I... POKED IT WITH A STICK.

Isn't it best to let Igor POKE IT WITH A STICK?

--
Scott

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