Looked around the site and couldn't tell if anyone had already covered this --
I'm making a puppet -- my original intent was to cast in foam latex, but I recently got a sample of Echo-Flex silicone to try, and now I'd like to cast with it.
Here's the catch, I already sculpted the figure with clay that I know is NOT sulfur free, but I haven't made the mold yet -- my question is: Could I spray the sculpt with a coat of Crystal Clear or some other sealer, thus making a barrier that would prevent the silicone from reacting badly?
Yes, if the coating really seals it. I haven't used Crystal Clear so I don't know for sure if that would do it.
In the past I have used a 2-part polyurethane floor varnish to seal water based potter's clay so I could make a polyester resin fibreglass mould - that was because the water in the clay stops the polyester resin from curing. The sculpt (a life-sized leopard seal) was too big to do in oil based plasticines, and I couldn't afford epoxy resins that don't mind a bit of moisture, so I had to find something to seal it. After the 2 coats of sealer I used some mould release wax, then pva release (that washes off in warm water), then wax again. It worked, and would probably seal off the sulphur in the clay just as well. But there must be sealers made for mouldmaking that would do the same thing.
The best thing you can do is put some sealer on a piece of the same clay, let it dry, then try painting the silicone directly onto that, and see if it cures. If it cures on that, it should also cure on a mould taken from it. I have a board covered in dabs of different clays where I tested to see if silicone would cure on top of it, but I didn't test sealers to see what difference they would make with a sulphur clay.
Wow, thank you, thank you! made my day.
Cool, I was hoping the answer was 'yes.'