Below, cutting the teeth away from the rubber jawset as neatly and carefully as possible, and then cutting holes through the entire thickness of the piece. Then, inserting it back into the original mold. The idea is to pour white resin into the mold for teeth, remove the blue part, and then pour pink resin for the gums.
Below, the final product. Not too bad. (Tangent alert- the stuff that looks like pink slime is in fact pink slime. When resin is overloaded with colorant it will not cure properly. I was using Smooth-Cast 65D here, a white resin, and I had to put in too much colorant in order to get a color other than very pale pink. The saints at the Smooth On tech support department recommended I switch to a transparent resin, Color Match 325, which I did.)
After I made a bunch more of these I decided this method may not be everything I hoped it would be. Sometimes pink resin would leak down over the white teeth and while I could carefully scrape it off before the resin set completely, this was something I'd rather not spend my time doing. Also, I would get thin spots or bubbles between the teeth and the gums at times, which would make for weak castings (I could crush in these spots with my fingers) which was definitely something I did not want. Time to try another method. Onwards!
Some sort of two part mold would seem to be the answer, one for the teeth and the other for the gums. My first thought was to cut the teeth out of a resin jawset with my Dremel, insert them back into the original mold, and make a model of just the gums from which to make a second mold. Below, getting ready to pour silicone for the model.
Below, pink resin gums cast from these new molds, with teeth inserted temporarily. Looks pretty good but....
Damn. The round thing in the middle is leftover resin that cured in the mixing cup. See how nice and smooth it is? See how full of bubbles the gums are? There's lots and lots of things that cause bubbles in castings but here it's due to replicative failure. Each time I demold rubber from rubber, microscopic layers peel away from the surface, creating these bubbles in the mold. (Even if I'm using plenty of release. Which can also cause bubbles, damn!!) Three times I poured rubber into rubber to make these, adding more bubbles with every step.
What to do next? Maybe at some point in the future I could investigate stronger rubber, but in the meantime, maybe I should go back to making molds from original sculpts whenever possible.
Below, the gums airbrushed and the frisket removed.
Not too bad, except that the paint was still fairly fragile and the frisket would pull bits of it off around the gumline. I was not convinced this would be the go to method.
Below, various airbrushing attempts, in various states of completion.A big fat pile of frustration.
Some of these are solid pink plastic, with the teeth airbrushed white; some of these are white plastic with the gums airbrushed pink. Ultimately, though, I was not happy with the durability of the airbrushed paint- even with the primer, and even sealed with a topcoat afterwards, it was too easy to scratch and damage. Maybe there is a method I hadn't discovered yet to make the paint more durable, but for the moment anyway I am SO DONE airbrushing these things for sure. On to plan B, attempting to cast in two colors of plastic!