Lost Wax Casting Process


I came across this process when I was trying to come up with an idea to cast a bronze sculpture I had in my mind.  After reading through this process, it helped me to better understand the process, and I would love to share it.  Site Credit following process.

 1. The artist creates a sculpted model, generally made of plaster, clay, marble, stone, or wood.




 2.The surface of the model is coated with a protective substance. Then the model is put into a bed of very fine elastic material held in place by a rigid outer mold. When the model is removed, its impression remains.




 3. Fireproof clay is carefully put into the impression, making a sharply defined duplicate of the artist’s original model.




 4. The surface of this second clay model is slightly scraped away. When this second model is returned to the mold, there is a gap between the model and the mold. This gap is where the wax will be poured. The final bronze will be of the same thickness as the gap that is created by the scraping.




 5.After closing the mold around the clay model, hot wax is poured into the gap between the model and the mold. This stage is crucial in producing a perfect reproduction of the initial sculpture. The result is a clay model covered with wax, which is then hand-finished to fidelity, incorporating the artist’s signature, cast number, and a foundry seal.




 6. A network of wax pipes, called sprues and gates, is attached to the wax model. These pipes will allow the wax to escape as it melts. The pipes will also spread the molten metal evenly throughout the mold and will let air escape as the metal is poured in.




 7. A finely granulated ceramic is applied to the surface of the model and its pipes until it becomes thick and coarse. The result, now called an “investment mold,” is then dried and heated causing the wax to melt and flow out of the mold, leaving a space between the fire resistant clay model and the investment mold. Accordingly, this method is called the “lost wax process.”




 8. The investment mold is then heated to a high temperature (over 1,000 degrees Fahrenheit). Except for a place to pour in the liquid bronze at the top, the mold is covered with a layer of cladding (a protective metal coating), which must be completely dry before bronze pouring begins.




 9.Molten bronze (over 2,000 degree Fahrenheit) is then poured into the investment mold, filling the space left by the “lost” wax. When all is cool, the cladding and investment mold are broken and the metal appears. The bronze sculpture and its sprues and gates are an exact reproduction of the wax in step 6.




 10. The network of sprues and gates is then removed and the surface of the bronze is chiseled and filed so that no trace of them can be seen. This process of hand-finishing the bronze to perfection is called “chasing.” Any remains of the fireproof clay model left inside the bronze are also removed now.




 11.When the chasing is finished, hot or cold oxides are applied to the surface of the bronze, creating a thin layer of corrosion. This layer– slightly brown, green, or blue in color– is called the “patina.” The patina protects and enlivens the surface of the bronze.



Ten Step Lost Wax Casting Process of Auguste Rodin’s Sorrow
Plaster, Clay, Wax, Ceramic and Bronze
10 Models and Final Bronze, approximately 16 x 11 x 11 in. each
Iris and B. Gerald Cantor Foundation

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One comment

  1. Howdy there,Terrific article dude! i am just Tired of using RSS feeds and do you use twitter?so i can follow you there.

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