Processing Silicone Prosthetics
After fibreglassing the moulds, drill the in the 6mm holes on the touchdown points. A recommended drill, and the ones used in the workshop are Mikata 18 volt drills. (The battery slots out and charges from the bottom. There is a clockwise/anticlockwise button just behind the drill head. There are torque settings - you want around 10-12 torque, too high and you can rip through your mould.)
To clean out the moulds:
- Liquid wax from PS composites
-poly wax mould release also works
-Cut down a cheap brush until its short and dense, apply o dap of either of these and work into the mould. Wash any residue out with sopay water.
Injecting the silicone:
-Apply mould release. A layer of Carnuba wax will work. Epoxy Parfilm is a wax free mould release that doesn't inhibit plat silicone. You only need a small amount of this sprayed on both the outside of the positive face mould and the inside of the negative fiberglass mould. They can be used in conjunction.
- Then apply 4 layers of the cap plastic and IPA mix. This can be carefully painted on or sprayed on with a catering oil spray re-usable air pump.
-Weigh out all your silicone and mix it just before you inject it into the moulds
- Make sure there is no air in the syringe or it will get injected into the mould which could cause air bubbles
- the injection hole should have been measured to be the size of the end of the syringe, you don't want it too big or too small or the silicone won't inject properly
- Put all the screws and wingnuts on prior to injecting but ensure they are a little loose so the silicone has room the spread
- Inject the silicone, working quickly to ensure it doesn't cure whilst working
- when you can see it leaking out, tighten all the screws and plug the hole with blue tack.
-The silicone will take about 15 minutes to cure.
Filling my Mould
Running my mould in gelatine
After releasing out my mould, I came to the realisation that the fibreglass has curved around the sculpture where the clay wasn't pressed down firmly enough. This meant that I couldn't clean out the mould properly, let alone run it. After scooping out the largest lumps of clay I used the vibrosaw to remove the excess fibreglass, which was quite difficult, given the detail and intricate nature of the mould. It did concern me that I might loose a little detail, but I wouldn't find out unless I treid running it. The angles were also difficult which meant I accidentally sawed over the edge a little bit, but not majorly. I then removed the rest of the clay using lighter fluid, boiling water but polywax mould release was the most effective.
I used carnuba was for mould release, then poured in the gelatine, and screwed the wingnuts tight. I opened it after half an hour and I think for a first attempt it came out well. There were a couple of very small areas where the gelatine hadn't reached, but the detail in the suckers (that I was worried I might have lost to the vibrosaw) was retained and picked up really well.
Debrecini, T. Special Makeup Effects. (2009) Elsevier Inc. UK.
Todd Debrecinis advice on injection filling.
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