The photo on the left shows Castaldo Silicone Rubber, a sketch of the  model, the sprued model, sprue former and mold frame. Note the black mark on the sprue former and also on the mold frame. This mark is to identify the orientation of the model. Parting cuts are made on the back, non-detail edge and knowing which side is front and which side is back is helpful.  A sketch is very helpful when cutting the mold.

The photo on the right shows the model starting to be packed in the uncured rubber. This rubber is about the consistency of soft clay and it conforms nicely around the model.

The packed mold frame is placed in the vulcanizer for one hour at 350 degrees F. After vulcanizing we like to cut the mold while it's still warm. A can opener is used to help to make the first opening cuts. Rubber is VERY springy, so care must be taken not to slice yourself with the scalpel.

A mold cutting frame is a safer way to finish cutting the mold. Notice the black marks on the frame to keep track of which side is which. A slight twisting motion of the knife as it's pulled towards the edge of the mold makes locks in the mold. These locks, sometimes called choppy water cuts, keep both sides of the mold in register when it's put back together for wax injection. Cutting the mold is a simple matter of carefully following the edge of the model.

The photo on the right shows wax about to be injected into the mold. The wax temperature is 150 degrees and injected at 7 pounds air pressure. The temperature and injection pressures are quite critical depending on the model, and wax used. The mold is held with even pressure using a pair of aluminum plates on each side of the mold and held by welders vice grips. The wax we like is Plast-o-wax since it's quite flexible and doesn't break easily.

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The finished wax pattern is ready to be invested for lost wax casting.