Multi-Piece Prosthetics

Dan Kurz

(Click on pictures for a larger version in a pop-up window.)

In this article, I will outline the steps I take when Designing a makeup and executing it. I recommend that you take a look at Bill Barto's (FX Man’s) article on the theory of this topic. I will attempt to expand his excellent article with a case study. This is how I do it and it works for me. You may find a better method. If you do, share it with the class.

To start, I took the life cast of the model and made a simple silicone brush up mold. Half the cast was molded from the ears forward and down past the collar bone. I then cast a hydrocal duplicate of his cast. You must make sure to keep the hydrocal thin. Hoydrocal is used due to the fact that it is porus and will absorb water in the floating stage. Once the duplicate cast is done it is coated 2 or 3 times with Alcote. Alcote is a dental separator and is available from most FX shops or your local dental supply house. Alcote shrinks a little as it dries, so if it flakes off, you have added too much….shame on you. You will know if it had dried if it has a slight eggshell sheen to it…and it’s not wet.

I have based this makeup on an elderly Native Canadian male. You can now begin sculpting the character on top of the cast as normal. Remember to keep the areas where the makeup will split thin. I sculpted the prosthetics as far as the detail. I didn’t add the texture as some will be lost during the floating and separating.

Here is a lesson in multi tasking; you should be making your positive molds while you are sculpting. I used the same silicone mold and poured in ultra cal 30 in the desired areas. I needed positives for the chin, forehead, neck, sides of the face and the nose/upper lip. These casts need a base to sit on so, when the individual casts are done, they need to be soaked for 30 min in water. This soaking ensures that the casts will adhere to fresh plaster. To make the bases, I used a roll of carpet with the rubber backing and cut them into strips. The strips are rolled up and made into tubes a little larger than each cast. The tubes are placed on a level surface and filled approx 4-5 inches full of ultracal 30. If the molds are to be used for multiple baking’s, it is advisable to reinforce them with metal mesh. Make a ring about an inch smaller than the diameter of the tube and place it in the tube before pouring the plaster. This acts the same as the rebar in concrete structures. Once the plaster has creamed (firm but still wet) the casts are imbedded into them. I blend the wet plaster to the cast with a brush.

Once the molds are done and the sculpt is complete, the life cast is then dunked in water. This is called floating. Before you dunk, use a sharp exacto knife and cut the sculpt where you want to divide it. You should use a large Rubbermaid bin or a garbage can and fill it with clean water. The cast should be submerged and left to sit for a few hours. To be safe, I let mine sit overnight. The water will seep into the porus hydrocal and re-activate the alcote in the other side. It will become wet and slippery and cause the clay to fall off. This is called floating because, in theory, the pieces should float off the cast, pretty clever huh? Don’t be so optimistic, you still have to pry off the pieces and large sections may have to be cut in half. I use a slurpee spoon straw to pry off the clay. Be gentle and patient. Dick Smith recommended to me that one use a water pic to aid in removal. Water could be blasted under the clay and force them off. I have not tired this but it sounds like it would work well.

You should now have the pieces separate and on the positives. It is now a matter of sculpting the detail and the blending edge. But what if you have pieces that are too thick to overlap? Areas like the jowls and chin can be too thick to overlap. There is a solution. Cut the pieces as normal and remove the chin for example. Clay is added to the two jowl edges to blend off to the life cast where the chin was. You then make an alginate mold of the area and cast your positive from that. You can then place the chin section on the cast and blend it to the jowls. Now it overlaps.

Once the prosthetics are too your liking, the cutting edge and the flashing are sculpted as usual. I used water based clay. I also added small rectangular holes in the flashing. This is to take some of the pressure off the cutting edge. This it not necessary, only a personal thing. The same effect is achieved with drilled keys.

The sculptures can now be lightly sealed. Try not to get much in the blending edge as it can affect its thickness. The carpet is again wrapped around the positives and taped closed. Ultracal is mixed and poured in as before. The molds are left to cure and later pried open. Clean the molds and drill a small vent hole in the center of the positive. I drilled mine in the center of the cheek, tip of the nose, center of the forehead and center of the chin. The neck was injected so numerous vent holes were drilled in the perimeter of the appliance and 1 injection hole in the center.

From here it is a matter of running the prosthetics and doing the application.

Dan Kurz is currently a student of Dick Smith and is building a portfolio. Dan is located in Canada and hopes to be working in some facet of the SFX industry. He would be happy to answer any questions, about pretty much anything... except math. The link to Dan's site will be restored when updated site information is available.