Plaster vs. Clay Moulds
When creating a new vessel for production an archetype, or patrix, was sculpted from clay. Using plaster or clay, a cast was formed around the prototype, which would dry and harden into a mould. Depending on the medium used, this process and outcome would differ. Clay moulds, unlike plaster ones, were removed from the patrix before they had fully dried. They required being kiln fired, which subjected the moulds to deviate or shrink from their original form. There was no such obstacle when using plaster. Once the mould had dried, it was removed from the patrix and was ready for use, yielding little to no structural irregularities at all. Despite the accurate replications, its surface was not free from media related defects. Small globules found on pottery were the result of tiny bubbles that had formed in the moulds. This was a common problem when working with plaster, though one that would reveal which method was used.