Foamed gelatin starting getting really popular just prior to silicone taking over. I've not heard of anyone doing it lately (I'm sure there are a few diehards out there!), but it's a very clever way to get light weight and translucency out of a piece.
Comments
All 3 materials are translucent, which means they can blend well with the skin, can be intrinsically pigmented with flocking, and look very natural.
Pros Aide:
Gelatin:
Silicone:
That's just a quick list off the top of my head and based on my own experience. If anyone else has any additions let me know and I'll modify the list.
/Chris
/Chris