HOW TO MAKE A MOLD
If the sculpture is large or has complicated parts then it will most likely have to be cut into sections so that it can be molded and then cast easily. The sections will later be welded back together and finished out. This is an 8 foot sculpture by artist Jerry Gorman that Miguel is cutting into sections for the mold making process.
A rubber mold is made first so that none of the detail is lost. This process requires about seven layers of brush on rubber. The rubber mold can not hold up on it's own so a plaster "mother mold" or outer mold must be made next.
This is what the rubber mold looks like encased in the plaster mother mold.
This picture shows the "shims" or plastic seperation lines that will help to keep the different sections of the mold from sticking to each other. A mold release is also used.
Once the mold sections are removed from the original then wax is poured onto or into the molds to make a wax positive. This way multiple copies of the original can be made from the same mold. The wax will be melted out later in the process
The wax sections are coated with a ceramic slurry that will form a hard shell the wax will be melted out in a kiln and the molten bronze will be poured into the then hollow shell. The wax sections are "sprued" so that when bronze is poured in the air can escape.
The ceramic shell is removed and the bronze is polished and ready for the patina. The bronze must be heated with a torch to prepare it to accept the chemicals for the patinas.