yoda1138 said:

Adywan, just on the offchance you may not have molded plasticine with Silicone rubber before, use plenty of layers of protective clearcoat first as plasticine contains sulphur and stops silicone curing making a right ol mess! I usually sculpt from Chavant or brown terracotta wax which is very soft and meltable. no release agent needed for these. I buy mine from http://www.tiranti.co.uk/

You most likely already know all this, but that 1% chance you didn't coulda been expensive mistake.

Thanks for the info. I actually didn't realise that plasticine was still made with sulphur. Damn. I'm pretty sure that the silicon i have is tin cure and not platinum so i should be ok ( fingers crossed). But i'll do some tests first anyway