This is the finished fiberglass mold. I trimmed and sanded the edges.
Below you can see the inside negative.
With a little sunlight:
A little damage. The mold cracked a bit when I was prying it apart with my wedges, but then while walking down the stairs, I tripped over the cat and dropped the mold to the ground. After a little bondo, it was as good as new.
Basically what I am trying to do is make a two part fiberglass mold that will be injected with silicone. In order to get a proper thickness that I wanted the mask to have, I needed to lay in a 1/4" bed of clay. I used Klean Klay. Below is the negative image. It's hard to tell if its negative or positive, but the shadows help.
I didn't take any photos of the fiberglass process, but once the clay was ready, I layered some glass on top of it. I drilled a few holes before taking it apart.
Even though I used a good mold release and Partall #10 the Klean Klay was heated by the curing and became diffucult to remove. The PVA also seemed to bond to the fiberglass shell and soaking it in water wasn't working to get it to remove.
I ended up having to scrape the entire surface with a metal tool, then scrub it clean. It took forever. Really annoying.
After the clay was removed, I drilled ventilation holes, then bolted the halves together. My injection syringe was originally an oil suction gun that I found at Harbour Freight. It worked perfectly.
As the silicone (tinted black) was injected, the air holes started leaking, and were plugged with clay. This method helps eliminate trapped air inside the mold. The silicone pushes it all out the holes.
The syringe was hot glued to a hole where the mouth will be, then I propped it up with some clay so it wouldn't fall and rip the hot glue off.
After curing, it came out like this:
Then I used a Dremel with a multi-purpose bit and cut the underskull out. I realize this means I no longer have a complete mold, but this saved time and money. I hope I don't have to remake the mold anytime soon.
Next: The Teeth!