The Lost Wax Bronze Process

To familiarize the bronze art collector with the "lost wax bronze" process, listed below is a step by step description of the procedure. It should be realized that this total casting process takes several weeks from start to completion. The artist's original conception of art may take him anywhere from a few weeks to several years 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, whether it is one of a kind or a recast of a noted collectible artist.

© 1995, EMI Reprinted with permission from EMI.

  1. Original Sculpture

    The first step begins with the artist creating an original sculpture.. This is usually created from wax or clay, though other materials can be used as well.

  2. Rubber Mold
    A flexible mold is made from the artist's original. This mold captures every detail put into the artist's 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.

  3. The Wax Casting
    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 a trained artisan 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, called 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 spree cup is placed onto the wax to receive the molten bronze.

  6. Investing
    The wax is then coated with an "investment:' a liquid refectory ceramic. Several layers are applied creating a stable mold which 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 into the form. The bronze is poured at a temperature of 2100? Fahrenheit. (Bronze is an alloy of 95% copper, .02% lead, .02% tin, .06% zinc. 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. Finishing

    An artisan cuts away the sprees and gates. Then by grinding, chasing, sanding and polishing, all areas are blended back to make the bronze look exactly like the artist's original sculpture.

  12. 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 a permanent part of the sculpture.
For Additonal Information about the Lost Wax Process see: "Lost Wax Bronze Casting" a photo essay by Harry Jackson, Published by Van Nostrand-Reinhold, New York City, copywrite 1978

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