Building models is never a clean process. When casting, I have to choose a material and a process that I think will give me what I want, try it, and see what I get. Occasionally, I get what I’m looking for, but more often, I get something that isn’t good enough and I either have to do something different with the same material, or I have to try another one. I have been trying to get a good cast of the abdomen of the bedbug for over a week. My first attempt was close using the West System epoxy with some intrinsic color. The color was off, but I added a bit of oil paint over the surface to get the right color. I would have to paint the surface opaquely to get the darkness of the blood under each segment. This is not what I want. The reason I have been going through all these gyrations trying to clear-cast is to get a translucence that I see on the actual insect under the microscope.
So now the problems….While casting under a heat gun (to kick the epoxy faster) both of my plaster molds cracked. This is the worst thing that can happen because the clay prototype is long gone and the only way to save the sculpting would be to make another mold off one of my casts (which I may still have to do). Instead, I am trying to repair the plaster molds by adding FGR plaster and fiberglass over the breaks. To make sure the plaster adheres to itself, I soaked the parts in the sink until I see no more bubbles coming out of them, and then I can add more plaster and it will stick.
One half of the mold was good enough to try another material: Elvax. I was introduced to this by Gay Malin at the New York State Museum in Albany. Elvax is very similar to hot melt glue. You can mix oil paint into it and get nice translucencies. This also didn’t work. While there was a translucence, the material is not clear and whitens a bit as it dries. Again I would have had to go opaque with extrinsic color to get what I wanted.
I realized that I have already been down this road with the mosquito model I did last year. The solution that worked then and where I am going now is vacuforming clear plastic and working the color up from behind the cast in silicone rubber.