Thank you for explaining everything so clearly! This has been a great help.
After a bad run with a Chinese factory I think I might give casting another go.
I've one question though; I'm reproducing doll parts which have channels drilled through so they can be strung with elastic. I'm planning on reproducing ones made of sculpey and I'm scared that even if I clog them up with plastercine the pressure pot will explode them or just force silicone into them. Sorry if it sounds silly. ^^;;; also sorry if this has already been explained.