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Lost Wax
Casting Processes By Keith Farley
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Did you
ever wonder or even consider just how an article of jewelry
is made? Some are fabricated from metal sheet and wire or a
combination of such components, adhering to purely metals
processes. There are, however, forms so complex that one
would be better served to approach using an alternative
process. What will be discussed here are those procedures
involved in taking the preliminary wax model and
transforming it to a metal replica of the piece of jewelry
to be. What follows will provide a brief description of the
lost wax casting process as well as different approaches to
it.
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Working With Waxes
There are many
varieties of wax, each developed with particular
applications in mind. Some waxes may be carved while others
may be shaped by hand, some cut from flat sheets, others
twisted, melted, heated, engraved, textured, or fashioned by
any number of methods to define shapes and details in the
wax. This area is quite broad and merits its own pages which
will be developed at a later point in time. For now, let us
assume we already have one or more finished waxes that
represent exactly the form of the object or objects we have
envisioned and are trying to achieve.
Spruing
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The term "sprue"
generally refers to a wax rod or series of these rods that
secure the wax model to a specifically configured rubber or
plastic base that is called a sprue base. In the center of
the base is a wax insert to which is attached one or more
waxes that are to be cast. On the outside is a lip that is
used to secure a stainless steel cylinder into which the
investment will be poured. The term, "to sprue" refers to
the development of a spruing strategy as well as the act of
physically attaching the sprues to the waxes and these to
the sprue bases. This process must be approached with care
and considerable thoughtfulness.
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Once the waxes have
been securely attached to the sprue base using sprue rods, a
stainless steel flask is carefully inserted inside the outer
lip of the sprue base, so as to surround the waxes while
still leaving, minimally, a quater inch space between the
wax and the inside of the flask. The flask pictured here is
the perforated variety, intended for vacuum casting which
will be described shortly. In this case, a sleeve must be
placed around the outside of the flask to prevent investment
from spilling out as it hardens before moving on to our next
step. A flask used for centrifugal casting is straight sided
with no perforations, simplifying the process of investing
the waxes.
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Questions
and comments? Please
email me here.
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Post Office
Box 184
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Telephone
(859) 635-1996
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Alexandria, KY
41001 USA
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Fax
(859) 635-6562
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http://www.artwork-inform.com
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