Custom Miniatures (LONG)

> Stuart M. Ford wrote:

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
so 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.)

Tom