Bronze Casting: The Lost Wax Process

All of my sculptures have been cast at a foundry located in Fort Collins. Tim Joseph, artist and owner of the Sculpture Center Foundry shared with me the step by step process involved in the "lost wax casting' process. Tim Joseph's work is second to none and I am grateful for not only the professional relationship we have established but for his friendship and mentoring as well.

To familiarize the collector with the "lost wax bronze" process, listed below is a step-by-step description of the procedure. My original conception of the piece may take me anywhere from a few weeks to several months to complete. Thus, realizing the time needed to create a single piece of bronze, the collector gains a greater appreciation for the value of his bronze.

1. Original Sculpture

The first step begins with creating an original sculpture. I typically create the original clay, though other materials can be used as well.

2. Rubber Mold

A flexible mold is then made from the original. This mold captures every detail of the original work, and is one of the most critical phases in the bronze process. This mold is used to create duplicates of the original design. This is where I rely on Tim Joseph, artist and owner of the Sculpture Center Foundry.

3. The Wax Casting Process

The molds are then used to form wax figures; molten wax is poured into the rubber mold, producing a perfect copy of the original sculpture.

4. Wax Chasing

The wax casting is removed from the mold, and one of the Sculpture Center Foundry's artisans hand- finishes the wax pattern to original perfection. Each wax casting is treated as if it were an original work of art.

5. Spruing

Wax rods (gates) are attached to the wax pattern to allow the even flow of molten metal and to alleviate the trapping of air and gas. A sprue cup is placed onto the wax to receive the molten bronze.

6. Investing

The wax is then coated with an "investment," a liquid re-factory ceramic. Several layers are applied creating a stable mold that is allowed to cure for several days.

7. Burn-Out

The piece, now coated in ceramic shell, is fired in a kiln. This bakes the shell and eliminates the wax, leaving a cavity in its place. (Thus, the term, "LOST WAX")

8. Casting

The ceramic shell is removed from the kiln and molten bronze is immediately poured at a temperature of 2100 ° Fahrenheit. (Bronze is an alloy of 95% copper, .02% lead, .02% tin, .06% zinc, and 4% silicon.)

9. Breakout

After cooling for several hours, the ceramic shell is carefully broken away, revealing the bronze sculpture within.

10. Sand Blasting

Fine sand particles are blasted under air pressure to remove the last traces of ceramic shell that adheres to the bronze.

11. Assembly

An artisan cuts away the sprues and gates. After this, the pieces of the sculpture are welded together by skilled craftsman.

12. Finishing

By grinding, chasing, sanding and polishing, all areas are blended back to make the bronze look exactly like the artist's original sculpture.

13. Patina

The chased bronze is now treated with chemicals and heat to give it the chosen color according to the artist's specifications. The patina is sealed under a wax coating and becomes part of the sculpture.

If you still have questions about the lost wax process for creating bronze sculptures, please feel free to contact me.