injecting the silicone

Preparing the mould for injecting requires bleeder holes to be drilled, these are 1mm holes at high points of the mould they are to let air escape when injecting the silicone. these holes are extended by using carbody filler that also has a 1mm hole drilled into it these are then attached with more carbody filler and a pin in the hole to locate it while it sticks then the pin is removed.
a poor tube is added this consists of drilling a hole in the internal mould piece, the tube is attached using carbodyfiller at the base and further up around the neck area.


next step is to apply the release agent. i used fairy liquid mixed with water at a mix of 50/50 it was painted on and left to dry, next a spray of apoxy par film. i used platgel 10 to encapsulate the prosthetic but you can also use cap plastic, Russel from mouldlife cautioned me against using cap plastic on a polyester resin mould as it can stick and be difficult to de-mould, i used a sponge to apply the silicone except around the eyes and mouth on these areas i airbrushed the silicone on, this creates a thinner layer for blending the edges. on the internal core mould i used strips of netting across the top of the head. the netting stops the silicone form stretching in none moving areas. the next step is to carefully piece the mould back together and then place the mould into a bucket to secure the mould for injecting.

The silicone:
to create a realistic feeling and moving look the plat gel 10 needs to be mixed with deadener. for this prosthetic i used 180% deadener to 50% part A and 50% part B plat gel 10, i also used a retarder to slow down the curing time because platgel 10 cures in under 10 minutes which is not enough time to de-gas and inject.
I mixed the pigment in to each component. to achieve the same amount of pigment in each component i drew a black dot on to the end of a mixing stick. this dot is used to know when the right amount of pigment is achieved. this is done by dipping the stick in to the silicone drawing it out and allowing the silicone to drain off, the dot needs to be visible but hazy if it is still too visible then more pigment is needed.

Injecting:

I used a total weight of 1200g of silicone and deadener. once i had the silicone pigmented i first mixed the retarder into part A then poured all the components into a bowl and mixed them altogether, then into the vacuum chamber to remove the air bubbles. Before i mixed the silicone i set up the giant syringe, which is just a drain blaster use for unblocking sinks from B&Q, into the pour tube. once the silicone is de-gassed i poured it into the syringe which is at a slight angle letting it drain down the pour tube then once it had drained fully i injected it slowly into the mould, and because i made bleed hole i new when it had reached to top, then i removed the syringe because the syringe creates a vacuum and could draw silicone out of the mould if left attached. I returned in the morning to de-mould. i placed the mould into a large tub of warm water, this activates the fairy liquid so the silicone is easier to de-mould.

it seemed to be working really well it came away from the mould easily and managed to remove the outer mould sections but when i tried to remove it from the internal core it became stuck to its self and unfortunately i was unable to save the silicone cast.the silicone should not have been sticky and could be the result of many things but i put a question out on the fxlab forum http://www.theeffectslab.com/forums/viewtopic.php?t=8554
and what came back was that i might of used too much fairy liquid, so i took the advise and mixed the fairy liquid with IPA at a much thinner mix, i painted it on making sure that there was no pooling of the liquid, then a coat of apoxy par film. this time when stippled on the encapsulating layer i made it thicker, i think that i had made the last one too thin and this contributed to the cast being sticky. I didn't airbrush around the eyes just a thin stippled layer. i used more netting on the head and down the side of the face close to the ear to stop over stretching. I only deadened up to 150% this time round, i think that it was too stretchy at 180%, there is a lot of weight on the cheeks and the the side of the head is thin so it needs more strength so i used less deadener. i did everything the same as before and when it came to de-moulding it came away even easier this time round it still seemed a bit sticky but is much better than the last one.

now on to cleaning up the cast. first i cut away the flashing and left a small trench along the seam line.
This trench is then filled with pigmented silicone which is deadened to the same amount as the cast, once that is done it is ready for painting.