Used by artists in special effects and doll making to create dynamic paint effects such as mottling.
These are made from a natural rubber. I have personally used these to paint silicone and found that the paint on the doll cures fine and bonds fine, but any paint on the sponge is inhibited. Heat curing is recommended if you use these. Please ensure that you do a test to check that the particular kind of silicone you are using and the original casting is compatible.