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Re: Custom Miniatures (LONG)

From: Thomas Corcoran <tomnaro@c...>
Date: Fri, 27 Feb 1998 19:26:38 -0800
Subject: Re: Custom Miniatures (LONG)

Stuart M. Ford wrote:
> I am considering making some custom resin miniatures and have been
> wondering if anyone on the list has tried this before.  
> [snip]
> The process I'm planning on using is to make a primary model of the
> mini.  Then create a mold using silicon rubber, which will be split
> in half (top/bottom).

	I have been making custom models for some time. I use plastic
and any
number of small parts.	Since the model need only hold together long
enough to make a silicon mold I don't worry about sturdiness.  I do
however worry about small holes and voids in the models.  The mold can
be wrecked by any air pocket.  I generally overcoat the finished model
in a thin solution of white glue and wipe off the outside of the model
(to preserve the external detail.)  Everything must be absolutely dry
before the silicon is used.

	I have abandoned the two-part (split) mold, since the ship are
small.	Getting the halves to line up is a pain.  My alternative is to
make the mold in two parts but leave out the separating coating between
the layers. Here is how you do it:

Make a frame (I use plastic strips) large enough to give at least a
quarter inch clearance on all sides of the model.

make a 1/2 inch thick pad of clay a little larger than the model.

press the frame about 1/4 into the clay.

press the model into the clay just far enough to be secure.

pour the first half of the silicon.  Let the silicon dry (12 hours).

flip the frame over and remove the clay.

(true split molds would now put a non-stick layer between the halves.  I
don't do that.	I want the halves to stick together.)

mark which end of the mold is the top with a pen.
(The top is the frame wall closest to the thickest part of the model.) 

pour the second half of the silicon and let it dry.

Remove the frame.

Start at the top of the mold (where it was marked) and cut into it with
an exacto knife.  Be very careful so that you don't damage the model.
(If you want to keep the model.)

Make the cut parallel to the two poured halves. Try to make the cut the
entire length of the model.  The silicon can take a lot of abuse, so
don't worry about bending it.

Extract the model from the mold.  Use the knife to cut channels from the
high points of the void to the top of the mold.  All of the air must be
allowed to escape from the cavity.

When pouring the resin, simply spread the mold apart with your fingers
and fill the cavity about half way up.	When you let go of the mold the
halves will pull together and fill the remaining space.

When the resin dries, trim the flash, and it is done.

This method give a resin copy with a flash line on only one side of the
copy.  The flash is usually paper thin and can be torn away with your
fingers.  My method is good for making molds of models that are less
than three inches long.  Anything larger should be made using a true
two-part mold.

The silicon material stays fluid for too long to just drop a model into
a box of the stuff.  The model would sink to the bottom and you would
get a super thin wall on one side.

This sort of thing take a little practice to get it perfect.
(mistake castings make pretty good debris and space junk.)  


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