A painting shell is a custom shaped acrylic covering that, when pieced together with an unpainted acrylic surface, makes up the final shape of the prosthesis. It allows the ocularist to see exactly what the paint work will look like after the final curing. Unlike what many patients think, the piece is not "glued" onto the painted surface. It is entirely discarded after the painting session.
Many ocularists have developed their own unique methods of fabricating a prosthetic eye that do not utilize a painting shell. However, this method works for me and I make one for almost every eye I paint. When other ocularists want to explore this method, I get a lot of questions about the techniques.
I noticed that most people struggle to separate the two pieces after it comes out of the mold because they're being too careful trying to preserve the dental dam. The video below shows how I separate the pieces. Remember the dental dam has no additional purpose once it comes out of the mold. Go crazy and destroy it!