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Casting Call: The Lost Wax Method of Bronze Sculpture Casting

Bronze sculptures are among the most durable of art forms, surviving sometimes over thousands of years. Have you ever wondered how bronze sculptures are created? Bronze, a combination of copper and tin, is a hard metal that cannot be easily formed when cool into the rounded shapes that are used in most sculptures. Therefore, bronze objects are usually shaped while hot by either forging or casting. Of these, casting enables the artist to most accurately create the desired shape and detail in a work of art.

The most popular method of casting throughout the ages is called the Lost Wax method and it dates back possibly over 6,000 years. Artisans of ancient Egypt, Mesopotamia, China and Africa used this method to cast weapons, tools, jewelry and household items as well as works of art. As a matter of fact, there is still debate as to who was the first to develop the technique. In the thousands of years since it was first used, the use of technology has improved the ease and accuracy of the process but the concept itself remains the same.

The Lost Wax method for creating a bronze sculpture actually begins with a sculpture that the artist creates in a much softer medium such as clay, wax or wood. Once the artist perfects the original clay sculpture, a flexible mold is made by coating the original clay sculpture with rubber, one side at a time. When the rubber dries, a protective mold of plaster is built around each half of the rubber mold. Molten wax is then poured onto the inside of the two rubber molds, creating two wax shells. The wax shells are joined together to create a wax copy of the original clay sculpture.

Now here is the most technical part of the Lost Wax method. A funnel-shaped pour-cup and conduits called sprues or gates are attached to the wax copy of the sculpture as well as a series of vents. It takes a lot of experience to position these items correctly to achieve satisfactory results. Read on and you will learn why these “technical features” are added to the process.

The wax sculpture is then covered with a plaster, sand and water mixture called an investment. The investment containing the wax sculpture is put into a hot kiln. First the wax melts and flows out through the sprues – hence the term Lost Wax. Then, when the temperature is hotter, the investment turns into a rock hard mold. So what is left is an empty cavity inside of the hardened investment mold.

Next, bronze is melted at extremely high temperatures and poured into the investment mold from the pour-cup through the same sprues through which the wax flowed out. Gases escape through the vents. After the bronze cools, the investment mold is broken away to expose the bronze sculpture! But it is not yet ready to be presented to the public.

The sculpture must first be cleaned and the gates and sprues cut off. The bronze is ground and welded to blend the surface texture, a procedure known as chasing. The final step in creating a finished bronze sculpture is treatment with chemicals and heat to give the sculpture a color or patina. The surface of the bronze sculpture may look like it is painted but it this is actually the result of a chemical reaction between the bronze, the chemicals, and the air.

One of the most best-known examples of bronze sculpture is “The Thinker,” created by Auguste Rodin, a French sculptor of the late 1800s.

Click here to see more of Rodin’s sculpture.


The Thinker necktie
from Amazon.com





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 About
 the
 Author

Diana Blake is a professional artist and art history enthusiast. Her fascination with art history began when she encountered European art firsthand during several trips abroad as a young adult. As she began to compose a portfolio for her own art career, she called upon what she had seen in Europe and extended her knowledge to other styles of art through profuse reading and exhaustive research. As a result, Diana has written more than one hundred articles in which she delves into a variety of art history topics and she has compiled a list of links that she believes to be invaluable for art history enthusiasts. In addition, she also reviews books and movies on the topic of art history and has assembled an extensive list of online stores that sell books, movies and gift items related to art history.
   You can see Diana's own artwork by visiting her site at www.dianablake.net.