Re: Figure Casting Question

Hi Allan,

>How does one go about casting figures, either with metal, or by resin
or
>something else, from an existing model? I have a very old, out of
production,
>never to see light again model I would like to copy. I was just
wondering,
>hypothetically of course, how you would go about copying such a figure.
>

I've had to cast bits and pieces in the past - custom designed or very
OOP
parts - and have had moderate success with a 2 part RTV mould, casting
in
both lead (melted old figures) and plastic.

If you're going to try plastic, you'll have to play a lot, and try using
something like the Alumalite casting plastic that sets up hard enough to
demould in about 5 minutes.  I did a concept model of a laptop computer
back in design school, and created all the keys using this stuff and it
worked really well.  It is very tough, but can be worked (sanded,
drilled,
filed) easily, and gives great detail.	As I said, it sets up hard quite
quickly - which is a LOT easier to work with than the stuff that takes
12
or 24 hours before you can demould.  For hobby casting, 5 minutes is a
whole lot easier when doing figures in batches and only a single mould
is
available.  There are two problems with this stuff, I found.  The first
is
that you don't have much "pot time" with the mixed material before it
starts to harden - only about 30 seconds - which means you have to pour
fast - not so good if you have big parts.  The second is that unlike
spin
casting, in which there is quite a bit of centri(fugal? pidal? I always
get
that mixed up) force squeezing air trapped "under" the poured metal out
of
the mould through very small holes cut at the end of gun barrels and
other
projecting bits (hence those very thin "streamers" of metal you
sometimes
see on figures off the top of their head, or toes, or gun or wherever),
with hand poured plastic, you're much more likely to get trapped air and
bubbles in the details of the figure.

If you hand pour lead/pewter (which you should do outdoors or in a very
well ventilated area... you can melt the lead on a hotplate, but it
gives
of some nasty vapours), you'll get better results with infantry type
figures or stuff with lots of complicated detail.  The Alumalite
material
can reproduce any detail that lead can, but the lead gets into the mould
better...  I think what happens is that the very hot lead causes trapped
air to expand greatly, and is more likely to escape because of it -
rather
than the plastic which just traps a bubble.  You can, as I suggested,
cut
very small holes in your mould at the end of "protruding bits", and hot
lead will force the air out these holes.  We use a pin vice/microdrill
to
create these holes - small enough that when you're finished drilling
them
through the RTV, it seems to close over them so you can't even see where
they are.

RTV itself isn't all that hard to work with.  It is nice to have a
vacuum
chamber to "degas" RTV (remove trapped air bubbles), but who has a
vacuum
chamber?  I get around this by being very careful when I set up the
mould
in the first place... Pour each half of the mould so that any trapped
air
will tend to rise up off the figure, and bubbles trapped in the RTV will
not actually impact the figure itself.	

Be prepared that if you do this home casting, you won't get as good a
result as a spin-cast figure.

Also, don't be surprised if the figure you get (if you use metal) is a
wee
bit smaller than the master.  Lead will shrink a few percent, and the
resulting figure might be a bit smaller if you stand it next to the
original.

Anyway, check out that FAQ someone posted... and feel free to ask
questions :)

I've done this a bunch of times and it seems to work ok for certain
types
of things.  Obviously you have to be careful about busting someone's
copyrights, but home casting can be a quite satisfying thing once you
play
with it a few times and get experience to work the bugs out...

-Adrian

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Adrian Johnson
adrian@stargrunt.ca
http://www.stargrunt.ca

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