Well, you can make more than 1 mold from the materials so that helps justify the cost at least to me. Think of all the body parts you can mass produce!

I've used smooth-on products before, well only one specifically. I used Dragon Skin as my mold. I got about 100 skulls out of it before it was toast. My burlap layered plaster mold shell outlasted the mold itself, which really suprised me. And for a release, I used some generic Canola Oil cooking spray.

I also went with 2lb marine foam for my mold for $62. It was cheaper, has a 25-30x expansion rate, and produces the same results. So more molds for less money.

Awesome work!....Great vids too.....

You mixed the silicone, plastic, foam...
So what kind of volumes (ounces, cups, etc) are we talking for making a skull with these products?

With my luck, I'd mix too much of this stuff and end up with a bunch of waste. Or, I'd fill the mold with foam and blow the whole thing into pieces when it expanded.

Can you give us newbies some estimates on the amounts used of each product?

Two more questions...

I'm assuming that you also use a release agent on the silicone when making the foam?

How would someone go about making the cast item hollow?
I'm thinking about using something like this do make multiple pumpkins as well as skulls.

Not sure about the releasing agent, but as far as making a hollow cast I would suggest trying Alumilite liquid plastic. This is a 2 part mix similar to the foams. Once you have it mixed, you pour it into your mold and "slush" it around the inside coating as evenly as possible. The liquid sets fairly quickly (about a min.) and you can use more than 1 slush for a more durable coating. This will leave you with a hard plastic "shell" that can later be filled with foam or used as is and is easy to paint and finish.