The mould making process
There are quite a few techniques that can be applied when casting. In this case, to make this specific necklace in question, the technique of lost wax casting was used, and because multiples of the same pieces were made, moulds had to be made. This is a brief overview of the process (follows the images above).
Make ‘investment’ pieces. This refers to the original silver piece that you want to make multiples of. It has to be as perfect as it can be because the mould picks up everything. And I mean everything. All the little scratches included.
Attach sprues. This is the metal stick attached to the larger bits with the waves (1st image)
Cut rubber sheets to the size of the mould (that rectangular steel thing). We needed about 10 sheets to fill one mould. At the same time, turn on the heat pressure machine (I don’t know what it’s called, sorry!)
Layer up the rubber sheets, with the silver investment piece in the middle
When the machine has heated up enough, place mould in between heated plates, and roll till the two plates are firmly compressing the mould. Leave for 20 minutes.
Go back to the machine and tighten the wheel, increasing the pressure applied on the mould. Leave for another 30-40 minutes.
It’s very hot at this stage, so specialised gloves are needed. Release the pressure on the mould and remove to a safe location for cooling (probably overnight)
Pull the rubber mould out of steel block, and cut (there’s a technique to this too!) the investment piece out.
Dust baby powder onto the moulds and inject wax to create wax models of investment piece.
Cast the wax pieces
Of course, to cast, there’s the other process of sprueing it to the tree and all that jazz, but that’s for another time!