Blackhawk Studios Tutorial: Foundry Process - Investment Molds

In this instance, a clay model is given a parting line by placing aluminum flashing into the clay along the proposed mold parting. Then the clay is coated with brushable latex, allowed to dry, then re-coated. This process is repeated several times until an adequate thickness is obtained. There are many options for rubber mold materials including silicones and polyurethanes.
The rubber mold captures very good surface detail. Small pieces of sponge are used to fill in undercuts, then more latex is applied over the sponges. Sometimes suare pieces of sponge are also used to "key" parts of the mold together for registration.
A plaster "mother" mold is usually cast outside the latex to stiffen the flimsy rubber mold. Sometimes a mother mold is made of more light-weight fibreglass.
After the latex mold has been cured in a slow oven (don't do this at home-it stinks) casting wax is melted and poured into the latex mold held fast inside the mother mold. The molten wax is sloshed carefully to evenly coat the entire inside of the mold. When the wax coating thickness matches the desired metal thickness any extra wax is poured out. The wax copy is allowed to cool.
Wax casting is shown still inside latex mold which is held firmly inside mother mold. When tha wax has cooled the mold will be carefully removed from the molds, which can then be reused.
This is a hollow wax casting from a latex mold.

Continue to Page Two

Joel McKinney Home
Address questions and comments to: