OK here goes. I built this vacuum form to make positives of faces to pre paint appliances and take them to set. So it is large enough to do a face and neck back to the ears.

Materials:
Shop Vac (I have a craftsman 6.25 horse power)
shop vac hose to hose adapter
small rectangular electric grill $23.00 at Walmart (it looks just like those
little Sunbeam tabletop gas grills)
Heavy duty cookie sheet, mine is 18"x13&1/2"
19"x13&1/2"x1/4" thick piece of plastic or Plexiglas
2 screen window frame kits
1/2 a sheet (4'x4') of 1/2" particle board or plywood
12' of 1/8" aluminum angle stock
1 tube of silicone caulk
assorted drywall screws & round head wood screws
2 Light switches with plates I use the ones that you just touch the top or
bottom not the old fashioned toggles
Matching wall socket and plate
some 14 gauge wire and wire nuts
2 pieces of 1"x4"x13" wood
(I built the machine out of what I had lying around so this is just a loose guide line for materials.)

Vacuum forming is simply heating up sheets of plastic until they are soft and stretchy then placing it over a positive form and using a vacuum to suck the plastic tightly onto the form. I have gotten very good detail with my machine, even pore texture from life casts! I had seen more elaborate machines with tanks, vacuum pumps, check valves etc. I just wanted to test the process and it worked so well that I have been using it ever since. In fact you may have seen pieces made on my machine on The tv show Angel and music videos on MTV.