The Lost Wax Method of Casting and Finishing Bronze

The Mold

The flexible rubber mold is made from an original sculpture or an exact model. This modern material is able to capture every detail. The master mold is cut into several sections for casting. A complicated sculpture may itself be cut into several sections to facilitate fabrication of the master mold.

The Wax Casting

Molten wax is then poured into the rubber mold producing faithful castings of the sculpture components. Each separate section will have a wax casting to be poured.

Wax Chasing

When the wax casting is removed from the mold, one of our artisan’s hand- finishes, or "trues" the details to perfectly match the original.

Gating and Spruing

Wax rods called "gates" are applied to the wax casting to allow the wax to be removed, and funnels, or pouring cups, called "spruces" are attached to receive the molten bronze.

Investing

The wax casting is coated with several layers of liquid refractory ceramic which resembles thin cement. It is then covered with special coarse sand and is allowed to dry. This step is repeated many times until a very thick coating has built up around the wax figure. This creates a stable mold which is allowed to cure for several days.

Burn-out

The ceramic mold is fired in a kiln, which bakes the ceramic and burns out the wax, leaving a cavity in its place. Thus the term "Lost Wax".

Casting

The hot ceramic mold is then filled with molten bronze at a temperature of 2100 degrees Fahrenheit. (Bronze is an alloy of 85% copper, 5% lead, 5% tin and 5% zinc.)

Breakout

After the bronze has cooled, the ceramic mold is carefully broken away by picking with a hammer, revealing the bronze form within.

Sandblasting

Fine sand particles are blasted under air pressure to remove the last traces of ceramic that adhere to the bronze. The sculpture is carefully inspected for correct form.

Assembly/Joining

At this point, if the sculpture consists of several different castings to make the whole (most sculptures do). The various sections are brazed together in the correct positions. A welding rod is used that is make of the same metal used to cast the sculpture.

Chasing

The raw casting is then turned over to another artisan who cuts away the "gates" and "sprues", blending these areas into the castings. He grinds off any sharp edges and again places any detail back into the work that may have been lost in the process at this point.

Glass Beading

To create an even finish to the surface of the bronze, the sculpture is subjected to glass beading, which is similar to sandblasting using extremely fine glass particles.

Polishing

The bronze is hand-polished to prepare it for patination.

Patination

The chased and polished bronze is now treated with chemicals and heat to give it the the desire color(s). Many colors are the result of different chemical applications or several coats of the same chemical to get a darker result. The combination of heat and chemicals creates a fused bonding on the surface of the bronze, different from simply painting the surface. The patina is now a permanent part of the sculpture.

Waxing

The sculpture is hand-polished wit a coating of wax, often with the application of heat, to create a lustrous finish to the patina.

Mounting

The bronze is mounted on a complementary marble base to complete its finished look.

Inspections

Repeated inspections and quality control checks occur throughout these processes to ensure fine results. Inspection is repeated again prior to packing and shipping to the client.

NOTE: Each sculpture is individually hand-assembled and may vary slightly. Measurements are approximate and in inches.