Casting the Jawbone

Photographs, river project, Work in Progress

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Casting the jawbone raised a host of issues that I didn’t realise would be a problem, but hopefully it will work out in the end. Before we could make a hot rubber mould of the jawbone Becky (the technician) and I decided to make a plaster cast of the jaw, as we felt it would be too fragile to make a hot rubber mould from directly.

STEPS

  1. Before we could begin casting I had to fill in the holes in the jaw (where the rest of the teeth originally were) with soft wax, so that it would be easier to cast. I also used a little superglue to secure the two teeth- we were worried that they may have come out of the jaw when we de-moulded it, so this was a preventative measure.
  2. I then pressed the jaw carefully into some clay and built up clay walls around it, and then applied a few layers of vegetable oil to the jaw to help release it from the mould once the alginate had set
  3. I mixed up a small amount of quick set alginate which I poured into the clay mould and left to set
  4. Once this had set I carefully removed the clay and rinsed the jaw and alginate, before greasing it up with more oil, and building up clay walls around it
  5. Another batch of quick set alginate was then poured over this, and left to set
  6. The clay was then removed, and the two halves of the mould separated and the jaw carefully removed.
  7. After cleaning both halves of the mould I fit them together and secured them with elastic bands, and was then ready to pour fine casting plaster into it
  8. The first attempt didn’t work very well and only the thickest section of the jaw came out, so for the second attempt after pouring in the plaster I moved the mould around to encourage the plaster to flow through the whole mould
  9. Once I opened the mould up I realised one half had not worked out, and the other half, where all the detail was, was too thin- to fix this I cut up scrim and layered that and some more plaster on top of it until it was thicker and stronger
  10. I then de-moulded it and created a hot rubber mould from that plaster cast. Because the detail was lost on one side I decided to make a flat mould, rather than a round one that needed to be cut open, to save materials
  11. The final photo on the slideshow is of the original jaw, first failed plaster cast, second plaster cast, and de-moulded wax cast of the jaw- as you can see there are a lot of details that need to be worked back into the wax by hand, but I am confident that it is doable

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