Since I decided to mold and cast my female turian mask using resin, rather than using latex like I did with Garrus, I wanted to do a quick write-up to show some of the differences.
Casting with latex (a soft material) is done with a hard, porous mold, usually made from plaster of some kind. Casting resin (a hard material) requires a soft, non-porous mold, in this case made from silicone.
Here, I’ve set the finished sculpt down flat and built a clay wall around her to prevent the material from dripping too much.
The mold material is a platinum-based brush on silicone called Rebound 25 by Smooth-on.. It’s thick, which makes it easy to brush over a three-dimensional sculpture like this! They also have a thickening additive called Thi-Vex which can be used to fill in undercuts like the inside of the mouth.
A silicone mold done over a three dimensional object like this is called a glove mold. Being soft, the silicone mold is not enough – it needs a rigid exterior mold to help it hold its shape while being cast. This is called a mother mold. There are several possibilities here, but I’m using an extremely lightweight epoxy putty called FreeForm Air.
The mother mold is being made in two halves, in this case. I first built a wall and mold keys (just from oil-based clay and pieces of cardboard), and sprayed it with mold release. Then, the FreeForm Air is applied to make the first half of the mold. Once that has set, the wall is removed and cleaned up. I added pieces of clay as pry points to get the two halves of the mold apart, sprayed the exposed first half of the mold with mold release, and then applied the second half.
When the mother mold is removed and the glove mold removed from the sculpture, you then reassemble it and you get something extremely creepy looking, like this! The mold turned out very nice and clean. I’m really enjoying working with brush-on silicone, it gives a great result!
Finally, here’s the first pull I did to test out my new mold!