Stage 3 - Making the Moulds
Production moulds were made by pouring plaster into the case moulds made in the previous process.
The mould maker would prepare the set of cases for pouring, treating the surface with a release agent, positioning reinforcing wires or frames and any other accessories to be built into the mould, during assembly.
Plaster and water were then mixed in a large tub. Using a bucket, plaster would be poured into each case whilst it was being rocked to spread the plaster and to eliminate air bubbles.
The plaster would set quickly and after a short period, the mould parts would be ready for removal. For heavy mould parts, fittings could be attached to the mould for use with overhead lifting equipment.
The complete moulds would then be assembled and spend three days in a mould drier before they were ready to be loaded onto production bench.