With the last of the carving completed and the hard edges softened with denatured alcohol it was time to make the mold.
Fiber Reinforced Plaster Mold
The material for the mold depends upon both the model material and the casting material. The model was a non-sulfur plasticine which is compatible with just about everything. The casting material was silicone so it made the most sense to make the mold out of a rigid material. I could have used a resin but it was less expensive to just use fiber reinforced plaster - which I already had on hand.