I've been planning to start an artwork project where I will basically sculpt decorative things and cast them for sale at an artwork market. While the casting silicone will be nothing but thinned out caulking silicone, the oil based clay I have used many times before is nothing but homogenized kid's play clay. I needed more of it for these sculptures and conveniently they had some at the local store. After homogenizing all the colors, it was pretty much the same stuff as the old clay I had, only it is much softer and quite sticky.
Not really good for intricate details then or sculpting of small figures and such, so I mixed it with my old clay that was actually too hard with hopes that it would even itself out, but it's still too soft and sticky.
Now I just need a way to harden the clay somehow, hopefully without having to evaporate the stinky oils in one of my cooking pots. I thought of maybe mixing it with a natural powder like flour, but then it hit me that one type of powder is actually used to dry out things; salt. My salt shaker makes a pretty fine dust, so I'll go ahead and try that now on a small piece, but in the meanwhile, does anyone know of any other ways to harden sculpting clay? Sure enough this is the place to ask about sculpting clay with all the damn good sculpters around this place. If my method works, then hey, maybe I've solved the same problem for you too if you have it.
EDIT - I changed this topic to also ask about the whole process in general since I also need to find a good casting silicone that is compatible with oil based clay. If you know of any, please let me know.