Wax Work |
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While wax patterns were originally modelled by hand,
and this can still be done, it is now possible to cast wax into molds
as well, so that multiple copies may be made even though the wax pattern
is lost in the process. Modern synthetic rubbers have been developed
which capture very fine detail and can flex to release undercut areas
of a model, greatly reducing the number of meld parts and the number
of parting lines necessary, when compared to the earlier technique of
using wet plaster molds. Waxes can be cast either solid or hollow, as
the wax will coat the inside of a mold after it is filled and poured
out. This process is repeated to build up the desired thickness of wax.
The process is slightly different for the smaller quantities involved
when making jewellery-sized pieces, necessitating some adaptations to
overcome the effects of surface tension, such as wax injection instead
of simple pouring, and the use of a vacuum table to extract full detail
from the molds.
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After it is made and touched-up, the wax model is attached to a "pour-cup", which is funnel-shaped to channel the metal into the meld from the outside, using "gates" or "sprues" made from rods of wax, and a venting system is made the same way to convey air and other gasses out of the meld when it is filled with hot metal. The wax head to the left is standing on the pouring cup with a vent to the chin. The cup acts as a stand during the shell coating stage. If you click on the thumbnail to enlarge the image, corepins can be seen quite clearly protruding from the surface of the wax. These will scure the core to the outer shell to enable a hollow casting to be produced.
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