In the third millennium B.C., somewhere between the Black Sea and Persian gulf, an artist crafted a vision in beeswax, covered it in liquid clay and cooked it in a fire. In the flames the wax was lost, replaced by empty space. Tin and copper - alloys of bronze - were gathered and heated. Once melted, the metal was poured into the cavity of the fire hardened clay. The metal cooled and the sculptor knocked the clay from the metal. The first bronze was cast!

Ancient "Lost Wax" bronze castings have withstood the centuries, visually telling the tale of past cultures, their religion and their social structures. The Greeks re-created the human form, Egyptian castings symbolized dieties, and Africans cast images of nature. Today, bronze casting is essentially the same as it was in 2,000 BC during the Akkadian period.

The Rubber Mold:

The metamorphosis of a sculpture from the original medium into bronze begins with a rubber mold. The original scupture must remain stationary during the mold making process. To accoomplish this, half of the sculpture is painted evenly with a clear, viscous rubber. When the half painted rubber dries, a protective and rock hard "mother mold" made of reinforced plaster is built around the pliable rubber. The sculpture is then turned over, and the process repeated. When the second side is complete, the mold is opened and the orginal removed from within. The rubber is rejoined with the other half, rendering an exact "negative" image of the sculpture in rubber.

The Wax Positive:

The original sculpture is now used exclusively as a reference point. From the "negative" rubber mold, a wax "positive" is created.

Wax is melted to about 210 degrees F, poured into the mold and evenly coated or "slushed" inside. Slushing is repeated three times using cooler wax each time to avoid melting the previous coat. When the mold is opened and the rubber peeled away, an almost perfect wax reproduction is removed.

Investing:

"Investment" is the process of building a rock-hard ceramic shell around the wax sculpture. Later, when the wax is melted out, the investment will serve as a mold for the molten bronze.

The wax is a "positive" which must disappear in order to create a cavity or "negative" for the bronze to fill. Thus, the "lost wax casting" comes from the process of the wax being melted , or "lost" from the shell.

The Pour:

A huge crucible, fired by a furnace, is filled with bronze ingots that are melted. The metal begins to melt at 1700 degrees F.

When the "Dance of the Pour" begins, the crucible is lifted by a crane out of the furnace. The molten bronze is poured into the ceramic investments with the wax inside. The entire pour is very fast and very precise.

Devesting:

"Devesting" is the process during which the investment is removed from the metal. Hammers and chisels are used to knock the investment off the solidified metal.

Metal Chasing and Finishing:

The bronze must be "chased" or cleaned to address the slight imperfections that may result from the casting. Metal chasing usually starts with large electric grinders, then more refined, smaller tools are used to re-create the artist's subtle surface texture.

Patina:

Patination is enhancement of the bronze by the chemical application of color. Three water soluble compounds form the basis for most patinas: Ferric Nitrate produces reds and browns, Cupric Nitrate creates the greens and blues, and Sulphurated Potash produces black. Each foundry develops it's own proprietary patinas that result from carefully orchestrated blend of different chemicals, pigments and application technique. The final step is putting a thin coat of clear wax over the bronze to enhance and preserve the patina.

Loading...
Enter your search terms below.