I was busy at Toy Fare last week, so sorry for the brief break. This week I am casting a tongue in my plaster mold. No release agent necessary, silicone really only likes to stick to itself and very porous surfaces. Rather than store bought pigments, I usually use oil paints. It doesn't take much, just a dot or two and I can usually mix the exact color I want (do not use water-based oils). I mix it into the the thicker half of the silicone mixture first and then use it ass a gauge of how well my silicone is mixed. I use a Smooth-On brand Dragon Skin silicone. It sets in about 15 minutes (that's a lot of slushing the mold around).
I add a second layer with a much richer red that will show through the translucent first layer.
Then I back it with a final stabilizing layer. Once the thin stuff has set, I know it's ready to demold.
::pop::
Ta-Daaahh.
Adding a think coat of clear for god measure and good sliminess.