Casting Problem.

[amalthea23]

Question! We're trying to make a cast of a sculpture made of Roma Plastilina with smooth-on moldstar. It's been sprayed with clear coat before pouring the smooth on, but whatever touches the sculpt doesn't cure properly. It stays gummy and sticks to the sculpt. Do you have any ideas as to what we're doing wrong, or any tips?

[mangozac]

I just looked it up and it seems that Roma Plastilina contains sulfur and this will inhibit curing of platinum/addition cure silicones. They do a professional version of the clay called Prima Plastilina which is apparently sulfur free, but that isn't much help to you right now! Your only solution will be to try some tin/condensation cure silicone, as it is less susceptible to curing inhibition.