1 - plastic (model) skull (remove/detach jaw)
1 - package non-drying clay
Plaster or Hydrocal (for casting)
some cheap brushes or makeup sponges to apply latex
Apply clay to the plastic skull model, filling in any undercuts (such as the deeper parts of the eye sockets and temple areas) and building up and sculpting areas (teeth, cheeks, forehead, etc.) to suit your personal tastes.
Apply liquid latex to the skull, covering the head from the roof of the mouth - around the face and sides - to the back of the skull. After coating the skull with at least 2 layers of latex, gently press a single ply of Kleenex onto the latex. Apply another coat of latex, soaking the Kleenex as you go. When this layer dries, repeat the whole process several times. (If you want a stronger but less flexible mold, use cheesecloth instead of Kleenex....and only reinforce the mold with 2 layers of cheesecloth.)
To separate the latex mold from the skull (after the latex had air cured), I cut a separation line through the mold at the back of the skull and another through the mold at the roof of the mouth. After removing the mold (and cleaning the inside of the mold) I used duct tape to re-join the mold separations (on the outside of the mold).
After mixing a batch of Plaster, I held the latex mold in my hand (face down - with my fingers in each eye socket) and sort of 'slush-cast' the plaster inside the mold. I continued to hold the mold until I could feel the plaster heat up (as it set) and gently set the mold aside as the plaster continued to set. To remove the plaster demon skull from the mold I simply removed the duct tape from the two separation lines and gently eased the skull out of the mold.
While the demon skull was still somewhat 'wet' (plaster will continue to dry out)....I carved additional surface texturing into the plaster. Due to air bubbles (and impatience) the horns have a rather interesting texture.....and I kinda liked it. : )
The skulls (plaster) shrunk a bit due to continued drying and were both sealed with extra coats of clear acrylic sealer last year.
THE EYEBALL: The eye was made by combining 1 part salt, 1 part flour and water until it is 'dough-like'. The dough was shaped and formed (like playdough) and baked at 275 - 300 degrees (F) until it was golden brown. Anything made this way must be well sealed as the 'dough' can rehydrate if it gets wet. I sprayed the eye with several coats of gloss varnish, painted it, and varnished it again.