Once the sculpting was completed, the
second mould making process could begin. As the prosthetic was a full-head piece
it was necessary to use a three-part mold to minimize the risk of the mold
locking against any undercuts or on any high points of the face.
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As with all other stages of the previous
mold making processes, the building of the dividing clay wall needed to be
meticulous. The first wall went from one shoulder to the other, across the top
of the head and around the ears. The ears were the trickiest area as half of
the ear needed to be in the front part of the mold, and the other half in the
back sections. Once the wall was completely smooth and stablised with
additional clay along the back, a thin layer of mod rock was also applied to
the back to strengthen it and ensure that the clay did not bow against the pressure
of the fibre glass. The keys could then be cut in, however, on this occasion I
opted for the simpler option of using a coin to make small, round indentations,
rather than cutting out inverted triangular keys. When the wall was completed
the fibre glass head then needed to be thorough released using mirror glaze to
ensure that the mould and head did not fuse together. A coat of macwax was also
applied to the clay wall to prevent the moisture from it from slowing the cure
of the gel coat. The fibre glass could then be applied onto the front of the
sculpt, beginning with a layer of tinted gel coat to ensure a thick and even
coverage. Despite using the macwax on the clay wall I still encountered a
problem with the gel coat failing to completely set and after 2 ½ hours of
waiting was eventually forced to continue with the fibre glassing process
whilst the gel coat was still tacky. The second step was to apply a layer of
resin, followed by chopped strand to ensure that all texture and detail of the
sculpt was accurately picked up in the mold. Following this a layer of very
fine fibre glass was applied, then two normal layers, an additional layer
around the flange and a final thin layer to smooth out the surface of the mold
and prevent any glass splinters when handling it.
Once the front part of the mould was complete the clay could then be cleaned away and a second clay wall with keys built running centrally down the back of the head. The fibre glassing process could then be repeated on one section of the mould, cleaned, and repeated again. When all three sections of the mould were completed and dried they could be popped apart using the same process as previously; with a chisel and wooden wedges before all three separate sections were then trimmed and sanded down.
The cleaning process probably required the most patience out of everything as it was very slow. The larger lumps of clay needed to be scraped out of the mould and off of the fibre glass head and collected up to be weighed. This would ensure that the right quantity of silicone would be used in the injecting process as 1g of clay is equal to 1g of silicone. I found that the easiest way to remove the remaining clay residue from the fibre glass head was using basic face wipes which worked surprisingly well. The mould, however, was a lot more difficult due to the amount of texture in it, which the clay really clung to. Despite going over the mould a number of times with face wipes a lot of clay staining still remained so I was then forced to go in with a toothbrush and panel wipe (transpired to be spirit based rather than naphtha based so did not work well) to scrub it as clean as possible. Finally I filled the mould with gelatine in a last attempt to clear out any excess clay, although this was not particularly successful.
Once the front part of the mould was complete the clay could then be cleaned away and a second clay wall with keys built running centrally down the back of the head. The fibre glassing process could then be repeated on one section of the mould, cleaned, and repeated again. When all three sections of the mould were completed and dried they could be popped apart using the same process as previously; with a chisel and wooden wedges before all three separate sections were then trimmed and sanded down. 
The cleaning process probably required the most patience out of everything as it was very slow. The larger lumps of clay needed to be scraped out of the mould and off of the fibre glass head and collected up to be weighed. This would ensure that the right quantity of silicone would be used in the injecting process as 1g of clay is equal to 1g of silicone. I found that the easiest way to remove the remaining clay residue from the fibre glass head was using basic face wipes which worked surprisingly well. The mould, however, was a lot more difficult due to the amount of texture in it, which the clay really clung to. Despite going over the mould a number of times with face wipes a lot of clay staining still remained so I was then forced to go in with a toothbrush and panel wipe (transpired to be spirit based rather than naphtha based so did not work well) to scrub it as clean as possible. Finally I filled the mould with gelatine in a last attempt to clear out any excess clay, although this was not particularly successful. 
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