Making the external shell – making the mold

Now that I have the quarter section of the sculpture I am making a mold so that I can cast the four sections that will make the external shell of the sculpture. I seal the plaster with two layers of water based varnish, put on two layers of release wax, two layers of PVA release agent and add some ‘cheeks’ so that I have a precise edge. The mold is made in resin and fibreglass using an additive to make it more flexible.

To release the mold from the quarter section I knock the mold once it is hard with a rubber mallet. This also breaks up the plaster skim which make getting the mold off quite a simple process.

I now have the mold which needs a little improvement before I use it for casting. I fill any imperfections with car filler and smooth the whole surface using wet and dry paper. This requires a lot of ‘elbow grease’!

Once it is smooth I add two layers of release wax and, on top of this, two layers of PVA release agent. This make a barrier between the resin and fibleglass mold and the resin and fibleglass cast ensuring they have not stick together.

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