Materials and tools are available for making molds in a variety of Rubber, Plastics and plaster. Molded objects can be cast in materials including wax, plastics, foam, aluminum, bronze and cast iron. Information on Metal Casting can be found Here
Mold materials can be purchased through a variety of sources, We tend to rely on
http://www.smooth-on.com Excellent company with excellent customer support for latex, silicone, urethane and casting plastics. Also carries mold tools, fiberglass, epoxies and resins for a variety of industrial and art purposes
http://www.polytek.com Polytek 74-30 is an excellent brush on or casting urethane rubber.
http://www.steffeyFindlay.com Located in Hagerstown MD, Carries a No1 Casting Plaster, as well as a variety of masonry, stone and other products
There are some low rent methods of making rubber and silicone molds, some of our favorite recipes-
- Gather up one tube of no 1 silicone, must be pure silicone cauk, not fast set or rain ready. you will also need 1 lb of dry plaster of Paris in a mixing container. A respirator is also recommended.
- Cut the top off of the tube of silicone and squeeze it out into the bowl/mixing container.
- Cover your hands in plaster like flour and thoroughly mix the plaster into the silicone in the bowl.
- When the mixture has taken the consistency of playdoh, press the mixture around the object you wish to have a mold of. The rubber will set in about two hours and can be trimmed with an exact-o or box cutter.
Spread on Silicone Cauk
- Gather Silicone Cauk, No 1, 100% Silicone, A can of Mineral Spirits or Naptha, Acrylic paint and Glycerine (available at most Pharmacies)
- Mix 1/2 Oz Mineral Spirits per Oz of Silicone in a container. More Mineral spirits will make a less viscous, but less forgiving rubber.
- Add 3 Drops Glycerine per Oz Silicone, and a drop of acrylic Paint to indicate mixing consistency. Stir quickly and thoroughly
- Brush or spread over mold surface.
- Mold will cure in about 2 hours. *(note- This method frequently requires a mother Mold for strength.)*
How to mix Plaster-
Step 1. Adding plaster to water?
Always add plaster to water, not the other way around. Water/Plaster ratios: By weight: 7 to 10. Add ten pounds of plaster to seven pounds of water. Calculate water needed for other amounts by multiplying plaster weight by 0.7. By volume: Add 2-3/4 lbs of plaster to a quart of water.?Use cool or room temperature plaster and water. Colder water may improve the strength of the plaster. It also slows the setting process. Never use hot water.
Step 2. Slaking, or resting stage?
Let the plaster sit undisturbed in the water for one to two minutes. (For less than 5 pounds of plaster, a minute may be enough; for larger amounts, wait two minutes.)
Step 3. Mixing?
Mix the plaster by hand or with a power mixer. Mix smaller amounts (under 10lbs of plaster) for exactly two minutes. Mix larger amounts for a longer time (e.g. 50lbs. for 4 minutes). Run your mixer at the highest speed that doesn’t trap air.
Step 4. Wait until the plaster is ready to pour?
Don’t pour the plaster right away. Take a minute to gently stir the plaster and bump the bucket on the floor, or slap it vigorously on the side to encourage air bubbles to rise to the surface. Carefully feel the resistance to stirring, and watch the shiny surface of the plaster. In a minute or two (sometimes more with very fresh plaster) you will detect a slight increase in the viscosity of the plaster and a lessening of the surface shine. Now is the moment to pour. Gently slap the sides of the mold to settle the plaster, or shake the table from side to side a few minutes.
Step 5. Setting up?
The plaster will gradually harden, release heat, and expand slightly (about 1%). In 25 to 35 minutes the plaster will feel very warm and hard. Remove the plaster from the mold or forms at this point.
Step 6. Drying the mold?
Don’t use your plaster mold until it is completely dry. This will take a week or more, depending on the thickness. You may speed up the process by setting the plaster in an airy, warm spot. Note: Do not put plaster in an oven or kiln to dry it. Temperatures above 125 F will damage the plaster.