Subject: Re: bronze casting

From: [email-masked] (G. Gary Preckshot)
Date: 10 Jul 1993 19:03:56 GMT

I've been actively involved in attempting to do bronze casting.
"Attempting" because I'm not there yet.  So far I'm hung up
getting the patterns right and I'm probably using the method you
might use - rubber molds to produce wax patterns which are
then encased in a ceramic shell, burnt out, and filled with
hot bronze.  As far as I can tell, you are sort of on your own
unless you can find a kindly foundryman to take you under his/her
wing.  It's not that bad if you aren't in a hurry.  You'll spend
a lot of time just producing a mold of the original without defects.
once you've got good waxes, you'll need to do a deal with a
foundry either to let you do the investment yourself or have
them do it.  Foundrypeople come in helpful, opinionated, or
obnoxious varieties.  I
've met one of each.  I'll let you know later when I get a
bronze done.

G.

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From: [email-masked] (Rich Feldman)
Date: Sun, 11 Jul 1993 04:26:09 GMT

[email-masked] (bill nelson) wrote:
>[email-masked] (Roger Mitchell) writes:
>: The most common casting method used among sculptors is the lost wax 
>: method... 
>: The second waxes are then dipped in investment (a wet plaster like material)
>: and allowed to dry and harden. After the investment is dry it is then 
>: baked...
>
>You have the general idea.
>
>The wax model is placed in a "cask", and the investment is poured
>around it.
>After the wax is burned out, the mold is heated to the desired casting
>temperature, then the molten wax is poured into it.  After the metal
                       ^^^^^^^^^^ with spectacular effect!  :-)

>cools enough to solidify, the whole thing is generally submerged in
>water, causing the investment to break down.

Then there is the new way, ceramic shell molding, to which Roger might
have been referring.  (ref. Methods for Modern Sculptors by Young & Fennell).
The wax pattern is alternately dipped in a special slurry, sprinkled with 
a dry powder component, and dried.  The cycle is repeated to build up a 
relatively thin shell (compared to a solid block of investment).  The
mold is dewaxed rapidly in a very hot kiln, so the outside of the pattern 
melts before the bulk of the wax expands and cracks the shell.

Apparently the shell molding media were originally developed for industry
(e.g. for turbine parts) but readily adopted by sculptors.
I have not used them myself.

-- 

Rich Feldman		Megatest Corp., San Jose, CA 95131
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