Molds, which are template forms for casting multiple identical copies of the mould design, can be created in many different ways. Some popular methods of mould making are creating one-part moulds, two-part moulds and three part moulds. Most moulds are made from a liquid material, which must be poured into a mould box or painted onto the model you would like to copy, but you can also shape a flexible solid material directly on your model. To use this type of mould on a sphere, you will be making a two-part mould.
Open your containers of Silicone Plastique Parts A and B. Mix each part together in equal amounts, kneading the material like clay. Continue mixing until the colours blend into each other evenly.
Coat your sphere model with mould release, so that the silicone material does not stick permanently to the model.
Apply the material to the bottom half of the sphere model, forming it around the bottom of the sphere. You can cover the model with a thin layer of silicone, so that the outside of the mould is spherical, or you can make a thicker, sturdier mould by packing on more silicone, so that the outside of the mould is square. A square mould will be able to stand up on its own.
Push any of the excess material up to the middle of the sphere and form a "ledge" there that sticks out away from the sphere, if you have not made a square-shaped mould. Press wooden craft balls into the top of the ledge, so that you will create keying impressions in your mould.
Strap the mould half to the model sphere, using a rubber band. Let the mould sit for one hour to cure.
Remove the rubber band and wooden craft balls. Coat the top of the mould half with mould release.
Make another mixture of Silicone Plastique. Form the mixture over the top of the sphere model, matching the bottom half. Let the mould sit for one hour.
Pull the mould halves apart and remove the sphere model. Place the mould halves back together, matching the keying impressions. Wrap a rubber band around the mould to hold it together.
Take an X-acto knife or craft knife and cut a small hole in the top of the mould, through which you can pour your casting material.
- "The Prop Builder's Molding and Casting Handbook;" Thurston James; 1989.
- MakeYourOwnMolds: Silicone Plastique Guide