In this case, I took the original cast, and laid it even, I achieved this by using clay to keep it upright on an even surface.
I made sure this on this stage I had my cast on a surface such as a wooden board before I began building up a base around the cast with clay. I also built a clay wall around the cast, this was to make sure that no silicone would run off my cast and make a mess.
The base I built around my cast then had 'keys' added to it. This is so when it comes to casting the two pieces can fit together correctly, to make the keys I simply pressed into the clay with the round end of a pipet, they don't have to be too deep!
Once the base of clay, keys, and clay wall have been added around the cast the silicone can be made and poured over it to create a silicone 'negative' of my cast.
To make the silicone I mixed Tinsil Gel 10 (part B) and a Catalyst, the mixture being 300g to 30. This can then be poured all over the plaster cast. Below is my cast after being covered by silicone!
This should be then left to set before jesmonite (which I used instead of plaster of paris this time) can be poured over the top. This gives the silicone a sturdy jacket, so when the silicone is removed from the cast it will hold its shape.
The jesmonite should have the same thick consistency as plaster of paris, above we can see it being spread over the silicone. To make the jacket even stronger, plastic matting was used instead of burlap, this is because it bonds much better with the jesmonite.
Here is the jesmonite jacket whilst it is drying.
The silicone negative shortly after removal.
Silicone negative of my original cast.
Once the silicone cast had been removed for the original cast, it could be then filled with more jesmonite and matting. I made sure the edges were thicker as these are normally the weakest parts of a cast.
My final cast! This can now be sculpted on!
The three stages of my second casting (the original cast in the middle, silicone mold on the right and my final cast on the left!)
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