"DoN. Nichols" wrote in message
...
5.Epoxy mixed with metal powder

Similar feelings about these -- except that they might handle
two or three -- depending on how well cooled the mold is.

If they are indeed used, I would suspect the binder burns out (*cough*) on
the surface, leaving a somewhat temp-resistant layer of filler.

6.Graphite molds is there a way for me to make mold using it. I Would
like able to pour it.

*Pour* it? Graphite is a crystalline form of carbon. According
to my old copy of the _Handbook of Chemistry and Physics_, carbon's
melting point is 1350 C

Whoa! You missed a rather large factor there, DoN. ;-)

Next closest thing I see on my periodic table is either terbium, dysprosium
or silicon. The latter makes the most sense since it's right below carbon.

As for carbon itself, it melts/sublimes (nearly the same at 1atm pressure)
somewhere around 4000°C, or about 7150°F. Just a *little* bit hard to
cast...

(neglecting whether it would form the right crystal form on cooling,
instead of diamond or some amorphous form)

Would be neat if molten carbon crystallized into diamonds, but unfortunately
that takes a lot of pressure, AFAIK. Although I think they've been getting
around the extreme pressure or temperature things with CVD (chemical vapor
deposition), I should read up on the current tech (if it isn't a total trade
secret).

Just to put it into perspective, that melting point, which was
given in degrees C (1350) translates to 2462 F -- well above what I can
reach (1850 F) in my metal hardening oven.

Within reach of a good foundry furnace, though. My graphite-based crucibles
aren't falling apart in the heat, so I think you grabbed the wrong number
;-)

And since carbon dust from the machining can be rather abrasive,
depending on how pure the graphite is

Actually, I'm not sure if purity is the cause. IIRC, "graphite" is made
artificially by heaping ground charcoal or coke, lampblack, other junk and
pitch together into an electric furnace. The pitch decomposes to either
amorphous or graphitic carbon, binding together the mass; the other material
is recrystallized by the intense temperature, forming a polycrystalline
block. I've heard the structure described as nodules, globs, flakes and
other junk. It's still graphite, but it's kinda random I guess, and that's
why it's abrasive.

I imagine natural graphite (probably damned expensive) would be wonderful
stock to machine.

I don't know what metals are a proper choice for glass molds,
but it would have to be something which could run at a temperature near
that of the molten glass, so you don't get a sudden cooling and
fracture your workpiece.

Eh- pressed glass is made in warm (dark red heat, probably 1200°F) cast iron
molds. Worked glass is formed with steel and moistened wood tools!
(Lichtenfrost effect, anyone?)

Tim

--
"California is the breakfast state: fruits, nuts and flakes."
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