TO MAKE A TWO-PART RUBBER MOLD
A COMPLICATED MODEL, PAGE 1
to make a two part silicone rubber mold or polyurethane rubber mold.
How to make an RTV rubber mold.
The first photo shows the original model for which we want to make
a mold. What makes this model complicated is:
• The holes under the neck and tail.
• The holes between the three feet on the ground.
• The leg lifted up and not touching the ground.
• The head and neck turned to one side and not exactly in line with
• The relatively thin legs.
The first step is to un-complicate the model as much as possible
before making the mold. We can make this model much less complicated
simply by removing the horse from the base. The base by itself is
a very simple mold - just put the base in a container, seal the
bottom edge of the base with clay so the liquid rubber does not
seep under it, and pour liquid rubber over it. After the horse and
the base are cast separately, they can be put back together. This
also allows for the flexibility of putting the horse on a different
base, or not using a base at all.
you are the creator of original sculptures that you will eventually
want to make molds from, always sculpt the main figure separate
from the base. And make other parts as separate objects also. For
instance, if this horse had a rider, you would want to sculpt the
rider as a separate object. If the horse was tied to a hitching
post, you would want to sculpt the hitching post separately, and
make a two part mold of this horse, we will first bury the horse
in clay, so that one half of the horse is in clay, and one half
of the horse is exposed. This means one half of the body, one half
of each leg, one half of the head and neck, and so on. The clay
will form what is called the “parting line”. There is no requirement
that the parting line be straight. It can undulate however necessary
to follow the curves of the model.
Use a pallet board. A good pallet board is a large plastic board
such as those sold as kitchen cutting boards. Roll out a slab of
clay about ½ inch thick on the pallet board, and lay the horse on
small balls of clay, and push them into place around the horse so
they come to the approximate parting line.
to Page 2
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