Loam mould - Lost Wax or Cire Perdu Process
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The principle is as easy as it is ingenious. You model your desired implement in wax, coat it with moulding clay, and fire the whole thing above 500°C. As the wax melts it produces a cavity with the exact shape of the model in the fired clay. You have just produces your first mould.
The moulding material for the lost wax process should possess a couple of properties: |
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- refractoriness
- permeability (to allow for gases to pass off)
- kneadable (for a good reproduction of the surface)
- rugged (to allow for handling the mould)
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| Bee's wax-models are in my case of a black colour for it is advantageous for judging the shape design. Because light reflexes are white, they are much more perceptible on black than on yellow. Any surface defects can therefore be spotted instantaneous. |
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Create a model using bee's wax. In this case it is a celtic ring from Switzerland |
| The model is now covered with the moulding material. This step is most important, since it affects the surface of the cast. Do any blundering here and you can throw away for mould right away. The clay should be applied uniformly and without fissures. |
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Firing turns the green clay lump into a mould. Due to the thickness of the clay cover the mould has to be fired for up to 24 hours. During firing the following processes may happen:
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- present wax (residue) melts and/or burns, this forms the mould cavity
- the free water evaporates
- chemically bound water disappears
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After casting the mould has to be destroyed to retrieve the cast. Here you can see a bangle. |
| The unfinished cast has to be worked to become a usable ring. The downsprue and the surface oxides have to be removed. The downsprue can often be chiseled off, the oxides have to be ground. |
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finished ring after grinding and polishing. The grinding was undertaken on several sand stones with different grit, the polishing with clay powder and leather.
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