Lost wax casting, sometimes called cire perdue, is an ancient method of metal casting where a duplicate metal sculpture is cast from an original wax sculpture. Intricate works can be achieved by this method, which is still widely used for art and jewelry today. Rings, pendants, bracelets, and even gold teeth are all commonly made via the lost wax process. 

 

The History and Evolution of Wax Casting

Lost wax casting dates back thousands of years, with its earliest known use in ancient jewelry making. Over the centuries, the technique has been refined and adapted, but the basic principles remain the same. It’s been used to create some of the world’s most famous sculptures, including those from the Renaissance era.

 

The Lost-Wax Casting Process

Lost wax casting involves several key stages, each requiring precision and care. Here’s a more detailed, step-by-step look as it would apply to the creation of a bronze sculpture (though this could be applied to other alloys & metals)

 

Creating the Model

The journey begins when you sculpt a model of the desired object in wax. This model is the exact replica of what you wish to cast in metal. The wax used can vary in type, ranging from beeswax to more specialized modeling waxes. The choice depends on the required detail and durability of the model that sculptors need to create.

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Investing the Wax Model

Once the wax model is ready, it’s encased in mold material. Traditionally, this material is a kind of plaster and silica mixture called investment that can withstand high temperatures. The investing process involves encasing the wax model in investment captured in a stainless-steel tube called a flask, ensuring every detail of the wax is captured.

 

Wax Removal

After the investment is set and hardened, the flask is heated in a kiln. The heat causes the wax to melt and run out through the channels called sprues leaving behind a hollow cavity in the shape of the original wax model. This step, known as burnout, is crucial and must be done carefully to prevent the mold from cracking or the details from being lost. 

 

Pouring the Metal (Bronze Casting)

After burnout, molten metal (in this case, molten bronze) is forced into the cavity left behind by the wax. There are two methods commonly used to accomplish this. 

1. Centrifugal casting, which uses a spinning mechanism to sling the molten metal into the cavity. 

2. Vacuum casting, which uses a powerful pump to suck the molten metal into the cavity.

 

Cooling and Quenching

After the metal has been poured, the mold is briefly left to cool. This cooling process is vital as it allows the metal to solidify properly. Once cooled, the flask is submerged in cold water to break up the investment and reveal the metal casting.

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Finishing Touches

The final step in wax casting involves cleaning and polishing the cast metal. Any imperfections, such as seams or leftover bits from the sprues, are removed. Further details can be added by the artist or craftsman, and surfaces are polished or treated to prevent oxidation as required for the final piece.

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Rubber Mold Making

When duplicates of an item are needed, rubber molds are used to produce duplicates of the same wax. These molds can either be vulcanized from layers of mold rubber with a metal master sandwiched between them. Alternative RTV (room temperature molds) can be made directly from wax or 3D-printed originals. As each wax makes one metal piece, being able to make waxes in quantity is the key to production casting. 

 

Investment Casting

Also known as “Precision Casting”, the investment casting process specifically uses a ceramic shell for higher precision and detail (whereas lost-wax casting can use multiple materials), making it ideal for intricate, identical industrial parts. Investment casting is more time-consuming and costly, focusing on detail and repeatability, while lost-wax casting is more versatile.

 

Foundry Applications in Art and Industry

In art, wax casting is revered for its ability to produce sculptures with incredible detail and fidelity to the original design. Artists can create intricate and delicate works that would be impossible with other methods. In industry, it's used for making jewelry, dental fixtures, and components for machinery and electronics, demonstrating its versatility.

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The Future of Lost-Wax Casting

Today, technology is shaping the future of lost-wax casting. 3D printing, for instance, is used to create more accurate models, expanding the possibilities for what can be created. Despite these advancements, the basic principle of lost-wax casting remains unchanged, proving its enduring value.

 

Lost wax casting is more than just a method for creating objects; it’s a bridge between the past and the future, showcasing human innovation and artistic spirit. Stunning jewelry can be created through this process. Lost wax casting remains a vital and fascinating process. 

 

If you'd like to learn more about Wax Casting, or about dozens of other metalsmithing techniques, check out our classes here at the Metal Arts Guild of GA!