Making the molds to cast the prosthetics from the sculpt is one of the trickiest, time consuming stages I found. Basically, and this is quite difficult to explain, you need a two piece mold of each plastilene model removed from the cast. The first step is to make a cast off the the original face cast, (this is a “positive” as the features stick out). The other is a “negative” (like the alginate from the face cast) mold of the plastilene model.
I haven’t got photos of most of this process unfortunately because I was panicking most of the time and forgot but I have taken lots in the secomd makeup I’ve done so will be able to show you more clearly. Will just have to try to describe what I did for now so skip it if you want 😀
For the positive casts I used alginate straight onto the cast (put vaseline on first as a separator) because the nose has undercuts round the nostrils so it’s better to have a more pliable substance to be able to remove easier. Hydrocal is used then to make a positive within the alginate but built up slightly. A round mold is then made with a piece of plastic, or rubber, or in my case wet clay and more Hydrocal is put into that to form the base. When this starts to set, the ‘positive’ nose cast is pressed into the plaster and smoothed round and the whole cast is allowed to set. When set the cast is completely hard the mold can be removed and the cast cleaned up and neatened with a good blade, and /or sandpaper. The final stage is to cut or drill keys into symmetrical places on the cast so when finished the two pieces will fit together neatly and securely.
The other pieces are made in a similar way except because of the lack of the undercuts the negative can be made with a cheap plaster of paris instead of the alginate. A sort of mold is made with wet clay around the area that is needed on the face mask and plaster is poured into that after applying a thin layer of vaseline otherwise it just bonds to it and is a big disaster :S Once the negeative is made then the same procedure is carried out as the alginate using a hard dental plaster, either Hydrocal or Ultracal 30 (which I used). Again it’s built up slightly and another mold is made to fill with the base plaster before the piece is added. When solid, it’s cleaned up and smoothed and keys are cut.
To make the negatives, the plastilene sculpt is added to the new positive again prepping with vaseline first. This is the time to refine the sculpt again as some of the detail is often damaged with it being handled and transferred. Once this is done the flashing has to be added which is really hard to explain again but hopefully it’ll be more clear with later pictures. Basically the edges of the sculpt are thinned down and smoothed to the plaster to create an edge that can be blended into the skin as easily as possible. Then ‘flashing’ must be made around the sculpt that covers any bare plaster only leaving a couple of millimetres inbetween which separates the prosthetic and creates a well for the excess prosthetic material to escape. When all this is sculpted and smoothed another thin layer of vaseline is added to the piece, the hydrocal in particular and the keys, so they can be separated again.
Again a wall of wet clay is made around the cast and Hydrocal/Utracal 30 is mixed as described previously and poured in to make the plastilene negative. Once hardened the clay is removed and the two casts carefully separated and cleaned up. This then provides the ‘sandwich’ of positive and negative casts with the space in between being the shape of the plastilene sculpt that can now be filled with your choice of prosthetic material again once it’s been prepped.
For the Basic Course Dick tells you to use a product known as Gel Foam Cubex which is basically a kind of gelatin which expands in the microwave to form a light flexible skin toned material which is really easy and convenient to use when you first start but apparently is only really useful for this type of thing and photos, because it can melt under heat of lights etc. The casts need prepping as I mentioned but vaseline isn’t good enough as a separator with gelatin so I decided to use a thin coat of Shellac (sort of polish/varnish) and then once that was dry, two coats of beeswax floor varnish that I buffed off afterwards. This prevents the gelatin getting into any of the porous surface of the plaster, (hopefully). The gelatin comes in blocks that you heat really gently on a low temp in the microwave til it becomes a smooth, pourable liquid. Great care must be taken not to overheat because the flocking that causes the pigment can scorch and become discoloured but more importantly air bubbles form that will cause problems with the finished prosthetics. Once fully melted it is carefully stirred again to avoid air bubbles, and poured into the negative of each mold and then the positive carefully placed on top using the keys for guidance. Quite a bit of pressure is applied as evenly as possible on each to make sure they are connected together properly and all excess is squeezed out.
The cubex takes around an hour at room temp to cool, bigger molds can take longer. Once they are cool though they are pried apart either by hand or with a chisel. To separate the prosthetic from the mold you need to use a brush and talc. Available surfaces are brushed with talc and the pieces still attached are gently lifted a bit at a time, brushing talc as you go to make sure the adges don’t stick together. Any remaining cubex can be reused at a later date so I wrapped it all in cling film to store. The finished pieces came out really well I thought (amazingly) and are shown below. I placed them back onto the positive of each mold and wrapped in cling film until they were ready to be applied.
These pics show the prosthetics on the positive molds with the keys. The nose photos were taken before they were trimmed but hopefully you can see the thinned area that once trimmed will blend into the skin surface.