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The Lost Wax Method by American Bronze Foundry Go here to visit our new Sculpture web site: http://www.sculpturegallery.com |
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1. The Original Sculpture. Our Fine Arts Engineer will study the sculpture. A determination is then made on how the sculpture will be "laid-up" or sectioned, if need be, for the mold making process. More complex molds will require the original to be cut into smaller moldable pieces. This is by far the most critical step of the procedure. All of the detail in the original sculpture must be captured exactly in this process. 2. Mold Making. The original sculpture is first sealed, then a mold release agent is applied to allow the mold to be removed without damaging the original sculpture. Depending on the artist's requirements, we will create a silicone, latex or polyurethane mold. |
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3. Now that the original sculpture has been prepped, the first coat (print coat) of rubber is applied by hand. The Master Mold Maker will assure that the entire sculpture is covered with a thin layer of rubber. Once the layer of rubber has set, additional coats will be applied along with "keys." This will help with the alignment of the mold when clamping or bolting both sides together. |
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4A. When the rubber is thoroughly set, a back-up shell
or "Mother Mold" is applied to support the rubber for
the wax pouring process. There are two types of back-up molds
we can construct depending on the structure of the rubber mold.
First, we apply a mold release to the surface of the rubber. If using a plaster mold, a plaster mixture is brushed on and strengthened with "hemp" (a straw-like material). A fiberglass mold has proven to be most suitable for the artisans to work with. It is durable, yet much lighter than plaster. After mold release is put onto the rubber mold, strips of fiberglass are applied. The fiberglass is then coated with a resin and hardener to bond it into a hard shell. When the first half of the mold is finished, it is turned over and steps 2 through 4A are repeated. Now the mold is complete. |
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4B.The back-up shell is removed and the rubber is gently pulled back so the original sculpture can be taken out. The rubber is then cleaned of any debris left from the original sculpture. It is now ready to receive the wax. |
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5. The Wax Pouring Process. The completed mold, having already been prepped, is now ready to receive the wax. The mold is separated and the first coat of wax is painted into the mold to capture all the fine details of the artist's masterwork. The mold is put together and more wax is poured in. It is then rotated until an even, thin coat of wax is obtained. Once it has cooled, a second coat is applied and rotated to achieve a thickness of 3/16 of an inch. The excess wax is poured out. After the wax has completely cooled, the back-up shell and mold are removed. Now the wax casting is revealed. |
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6. Wax Chasing and Spruing (Gating). Our skilled artisans will now clean the wax, removing any seam lines from the mold or slight air bubbles that may have occurred in the wax pouring process. Wax gates and sprue bars are attached to the sculpture along with a pour cup. The cup will receive the molten bronze, then bronze will travel down the sprue bars and fill the sculpture. The gates will serve to release air that is forced out when the bronze is poured in. |
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7. The Ceramic Shell (Slurry). In this process, we are now making a secondary mold. The prepared wax casting is dipped into a liquid binder material (slurry) and covered with a fine ceramic shell. Once it has dried, the process is repeated. Now with two coats of binder and fine shell, we move to a courser shell. This process will be repeated 7 to 10 more times before the shell is built up strong enough to withstand the molten bronze. These ceramic coats go both inside and outside the original wax, which allows the bronze sculpture to be cast hollow. The shell will remain in the slurry department for up to two weeks. This department is constantly monitored for temperature and humidity control. Skilled technicians at our in-house laboratory test slurry samples daily to maintain constant accuracy. |
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8. The Casting Process. The ceramic shells are moved directly from the slurry department and placed in the kiln (cup side down). This allows the shells to cure (bake) and the wax to flow out as the shells are heated to 18000 Fahrenheit (The Lost Wax Process). At the same time, bronze ingots are placed in a crucible and melted to 21500 Fahrenheit. Once the shells are de-waxed, they are cooled and inspected for cracking or possible defects. The hollow shells are placed back in the kiln and reheated to 18000, then placed in the pouring pit. Molten bronze is poured into the shells and allowed to cool and solidify. |
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9. Knock Out. The majority of the shell material is now removed inside and out, and the unfinished bronze casting is revealed. It is then glass beaded to remove any remaining shell material from the intricate details of the casting. |
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10. Welding. If the original was sectioned into multiple pieces, it would now be carefully fitted and reassembled. A visual inspection is done to check for any casting inclusions. Mounting studs are also added to hold the finishing base. |
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11.Metal Chasing. Now the sculpture is sanded/chased to remove any sign of welding and to prepare the bronze for the patina (coloring process). Several different sanding and detailing tools are used to give the best surface possible without disturbing the original texture of the sculpture. |
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12.Patination. The patina is the finishing color. Depending on the artist's requirements, we may use a variety of different chemicals which react to achieve a certain look. Colors like Museum Brown, Antique Brown, Multi-color Antique Green, Verde Green and Gold Leaf are just a few we can offer. After the patina is applied, we will seal the sculpture with a wax coat to protect the finish. Outdoor finishes are also available. |
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13.Mounting. Depending on the artist's preference, the
completed bronze sculpture is now mounted on a custom marble
base or pedestal. Our in-house marble department enables us to design a custom marble base to complement any sculpture. Murray's Sculpture Gallery has been on the web since April of 1995. Now we have just launched a new web site dedicated to sculpture only. Go here to visit our new Sculpture web site: http://www.sculpturegallery.com |
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