I have conducted research into making press moulds, witnessed them being created and have even created my own during recent work experience. From this, I drew up a series of plans that I have since followed- and I am pleased to say that, though rather lengthy, I found the process is relatively easy! Despite using different, more cost-effective materials, everything worked as I had hoped to produce a quality end result.
The first difference between my mould and the ones I have seen previously is that I have used Plasticine as opposed to clay to sculpt the base. The resin used professionally is very expensive, and so I opted for Plaster of Paris instead for my mould mixture, which was cheap. The mix I bought was a hard plaster, suitable for making one or two part moulds. Plasticine is a good base for such a porous material since it is waterproof.
I used two same-height blocks of wood and a rolling pin to get an even, uniform slab of Plasticine for the base to be built from. Cling film was placed on top of and beneath the Plasticine to prevent it from sticking to anything as it was rolled flat. As per my designs, the surround for the mould was created from foamboard, cut to size (in this case, longer sides of 9cm x 6cm, shorter sides 6cm x 6cm) and assembled to form a rectangular container.
The baked Sculpey mouth template was pressed into the surface of the Plasticine. The benefit of using a hard solid template is that it can be pressed into the base, and also later removed from the mould, without being damaged. The Plasticine was then built up around the mouth to meet the seam line, and smoothened as best as I could.
The foamboard container was placed around the base. Angled pegs were then sculpted and attached to the surface to align the mould halves, making sure than all gaps were sealed so that plaster could not run underneath.
The base and container were then secured atop a spare piece of wood, sealed airtight using a glue gun. The solid mouth was coated with a thin layer of Vaseline so it would not stick and could be easily removed from the plaster mould. The plaster was mixed according to the instructions, and carefully poured into the mould. Though the instructions indicate that you can de-mould the plaster after 30 minutes, I decided to wait a few hours just to be on the safe side.
The foamboard was cut away to reveal the solid plaster atop the Plasticine base. I was very pleased that the two halves prised open easily, leaving me with the first half of my press mould completed! Everything was tidied up with a blade and fine sandpaper, though the appearance of a mould is not what counts in the end! The real test will be whether or not it works to produce the correct shape.
The second half of my mould needed to be created directly upon the first half, albeit with some channels added to allow any excess Plasticine to be drawn away as best as possible. Of course, when moulding atop a shape everything needs to be inverted, and so these channels are built up on top of the first half with Plasticine.
The process from before was repeated, with a container built around the shape in which plaster would be poured. I was conscious that the two halves, both being plaster, might fuse together- and so coated the entire thing in Vaseline to keep the plaster from bonding to the surface. It was important to place the template mouth back into the mould to shape its reverse side. Again, I was very happy that everything worked well, and upon taking the mould apart and removing the Plasticine, my press mould was complete.