I applied silicone to the back of the head, let it dry and a shell of expanding foam came next.

Checking the fit of the two parts.

Applying some mold release fluid. This turned out to be an unnecessary step when molding expanding foam within a silicone mold. The silicone mold allows all kind of materials to peel out without difficulty.

Ready to mold.

Next I prepared to make a foam head in my mold. I used cans of cheap "Good Stuff" expanding foam. These are pretty cheap, but once you start using a can of expanding foam, the foam tends to harden in the nozzle, locking the unused portion of the foam inside the can.

How much is inside Expanding Foam
http://www.cockeyed.com/inside/foam/foam.html

After I sprayed a heap of expanding foam into the mold, I carefully cleaned the foam nozzle with q-tips, trying to keep it clear so that the can wouldn't be sealed shut the next time I used it.

The can felt more than half full, and I tried to estimate how many cans of foam it would take to make 12 heads.

I planned to control the numerous camera flashes with two rotary switches. Rotary switches put 12 switches behind a single knob. With a twist of the knob, I could fire off a bunch of camera flashes, rapid fire.

A ketchup bottle would be the switch box. I'd transform it into a camera later.

With trial and error I found what I thought would be the best spots for the knobs to be positioned on the bottle and marked them with a pen.

Then I heated up a nail on the stove and melted some holes into the plastic.

The knobs mounted.

Now I control your hamburger.

I had been cautious not to overfill the mold, but not cautious enough. Left to dry, the first head overflowed and created a bulbous neck of foam.

The head looked pretty good! The surface was somewhat pitted with voids, but I knew I could fill those with spackle or something else before I painted them.

It was very, very lightweight.

I poked a wire through to hold the head to the pvc rack.