How Is A Bronze Sculpture Made?

I’m sure I can safely assume you’re not wondering how one carves or molds a sculpture. Although the carving and modeling methods require great skill, the techniques used are fairly simple- you basically use tools and your bare hands to “add” or “subtract” material until you get your desired product. Once you have carved away from a stone or other hard surface, you can sand it and polish it. If you were carving from clay the last step would be to fire it in a kiln or heat it in an oven.

But how are bronze and other cast sculptures made? It’s not like there’s a chunk of metal and the sculptor chisels away at it. Casting is a little more complicated than the other two types of sculpture. It takes a team of several people, a foundry, and a 10 step process that has been around since 3000 B.C. When completed, you will have a work of art that will be around for that same amount of time into the future.

In a nutshell founders reproduce in bronze a sculptor’s plaster original. The process is a back and forth system of molding until the final mold is made to withstand molten bronze. This is how it goes:

1. The sculptor creates a model, usually plaster, to send to the foundry.
2. Using elastic material in a solid container, the founder makes a mold of the model.
3. The mold is used to make a model of fireproof cement that will serve as the core of the bronze during casting. Iron shafts are inserted to make sure it remains stationary within the mold.
4. The surface of the core is worn down, creating a narrow space between it and the mold.
5. Melted wax is poured into the mold, filling the space between it and the cement core. The mold is then removed, revealing the core shape covered with a layer of wax. The artist’s signature, the casting number, and the foundry stamp are imprinted in the wax.
6. A network of conduits is created to allow the melted wax to run out of the mold when it is heated. Later the conduits will also be used to pour in the molten metal.
7. A second mold is created of fireproof clay. When it is sufficiently thick, and throughly dry, it is heated, both to melt the wax and to harden the clay.
8. The fireproof mold is then covered by an exterior mantle of fireproof cement.
9. The mold is fired at high temperature. Molten bronze (2850° F) is poured into the space formerly occupied by the wax. After the bronze cools, the mold is broken to reveal a bronze replica of the model.
10. The conduits and other protuberances are removed from the bronze figure, which is then finished with chisels, polished, and treated with chemical solutions to give its surface the desired patina.

So there you have it. An artist can have their sculptures cast in bronze by sending it to a founder and paying them to do all the hard work. After all, you’ve done the easy part by creating the object in the first place. It must be interesting to see the final result, one of your own sculptures actually made in bronze, to be around forever.

Article by Daniel Kretschmer
Dan Kretschmer keeps a daily blog at www.vincesear.com. (Original title: ‘how is a sculpture made?’)