Rubber is mixed and poured into the mold. Most rubbers generally take overnight to cure. The rubber curing time is dependent on the type of rubber and it's cure, and the temperature in the room.

Rubber

After the second side is cured the mothermolds or plaster "shells" are removed (see above). The two rubber sections are then peeled off the original and set back into there own mothermolds to keep their shape. There are various ways to store rubbermolds. Closing the mold and pouring wax into it was the most common method in the past. Today, mostly because of cost, foundries will resort to using plaster. In time, this dries out the rubber. I suggest you store your "own" molds in a dry location. The mold sections can be stored (rubber up) separately without wax or plaster and placed into a plastic bag.