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Bronze Casting Information and the process of Bronze Casting
Category: Technology
Learn about the basics of Bronze Casting, types of Bronze
Casting, and the process of Bronze Casting.
Bronze has been the most sought-after metal for cast metal
sculptures in the bygone years. Bronze alloys have a desirable and unusual
property to expand slightly prior to their setting. This helps a great deal in
filling every corner of the mold. Their ductility and strength causes them to
be molded into any form. However, bronze has a basic disadvantage of not being
durable. Hence, there are hardly any traces of ancient bronze statues found.
Bronze casting generally takes place by a process called lost-wax casting.
Though, centrifugal and sand castings are also employed, around 90% of bronze
casting takes place through lost-wax casting.
Lost-wax method:
Lost-wax casting, in the industry, is better known as investment casting.
It is costlier than die and sand casting, but outshines them in terms of
accuracy. It is easily possible to make complicated structures through
?lost-wax casting’. The process can be described as follows:
Sculpting: First,
the original artwork is created by the artist from clay, wax, or some other
material. Mostly, clay (oil-based) and wax are used due to their property of
retention of softness.
Mold making: Majority
of molds consist of 2 pieces, along with a shim placed between 2 halves at the
time of construction in order to put back the mold accurately. Keys are kept in
the shim. The small sculpture molds generally consist of plaster. Fiberglass
can also be used. To have the minute details preserved on the surface of
original artwork, there exists a mold inside. It is made up of vinyl, silicone,
or latex supported by plaster part of mold. Generally, the destruction of
original artwork takes place during making. This is due to the solid nature of
the originals. The other reason is the rigidity of the originals at the time of
removal of plaster mold. That’s why; the original is cut off into thin, long
pieces and separately molded. At times, a number of molds are required for
recreating the original structure.
Wax: After
the completion of latex-and-plaster mold, the pouring of molten wax takes
place. Then, swishing is carried out till a uniform coating is obtained. The
thickness of the coating is 1/8 inches. The mold’s inner surface gets covered
by it. This process is repeatedly executed till the preferred thickness is
attained.
Wax removal: Artwork’s
?hallow wax copy’ is detached from mold. This mold may be reused by the artist
for making more copies of wax, but its use gets restricted due to frequent
?wear & tear’. Around 25 copies can be made for tiny bronze artworks.
Chasing: The
chasing of each copy starts. Rubbing of the marks is done by a hot metal tool.
The marks showing ?flashing’ or ?parting line’ are rubbed out.
Spruing: The
spruing of copy generates paths to flow (for molten bronze) and causes air to
move out.
Slurry: The
dipping of sprued copy into a liquid silica slurry, and then into sand-like
?stucco’ takes place. This process is repeatedly carried out till the coating
attains thickness of at least ½ inch.
After these steps, the out-and-out processes like burnout,
testing, pouring, releasing, metal chasing , and patinating are carried out.
About the author
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Tags: 2 pieces, accuracy, artwork, bronze alloys, bronze statues, ductility, fiberglass, latex, metal sculptures, minute details, molds, plaster mold, rigidity, sand casting, sand castings, sculpture, silicone, softness, traces, wax method