CHARLES MOORE
DBA HULA LAMPS OF HAWAII
74-5599 Luhia St. Unit F-5
Kailua-Kona, HI 96740-1677

Fax 808-331-8533
Local phone 808-326-9583
Toll Free: 1-800-421-5931

E-mail: lamps@aloha.net

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The Art of Lost Wax

Bronze is one of the oldest alloys known to man. The discovery of bronze dates back to 3800 B.C. when its was realized that the addition of a small amount of tin to molten copper resulted in a durable metal. This discovery led to the Bronze Age, a stage of civilization between the Stone Age and the Iron Age marked by widespread use of bronze in the production of tools, weapons and other objects. Soon crafters began using bronze in art. Bronze is one of the most durable metals on earth. It survives wars, earthquakes and volcanoes. Civilizations have vanished but their bronze artifacts are still in existence.

In the third millennium BC, 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.

Hawaiian Artist Charles Moore

Ancient "Lost Wax" bronze castings have withstood the centuries, visually telling the tale of past cultures, their religion and their social structures. For example, Chinese bronzes depicted ceremonial images; Indian and Egyptian castings symbolized deities; Africans cast images of nature; and the Greeks re-created the human Form. Many of the cultures have grown obsolete, religions have evolved and societies have changed. Elements of the "Lost Wax" process have been refined. Yet today, bronze casting is essentially the same as it was in 2,000 BC during the Akkadian period.

Modern sculptors who want their pieces cast in bronze depend upon a Foundry. There, artisans skillfully apply the "Lost Wax" method to wood, stone, clay, plaster or any other kind of Sculpture to transform it into bronze.   

The Rubber Mold
The Wax "Positive"

Applying the mold

The metamorphosis of a sculpture from the original medium into bronze begins with a rubber mold. The original sculpture must remain stationary during the mold making process. To accomplish this half of the sculpture is nestled into a base of soft plasticine clay; the other exposed half is painted evenly with a clear, viscous rubber. (Polyurethane rubber is best for single or small editions while larger editions require silicone rubber.) When the half painted with 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 original removed from within. The rubber is rejoined with the other half, rendering an exact "negative" image of the sculpture in rubber.

Wax is melted to about 210°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. Under ideal conditions, the wax wall will be about 3/16" thick --- any less might create flow problems for the bronze; any more will result in a heavier than necessary sculpture. When the mold is opened and the rubber peeled away, an almost perfect wax reproduction is removed.

Wax Chasing - Spruing & Gating

Wax Chasing Spruing & Gating

"Wax chasing" is the delicate process of joining the wax pieces, removing seams and repairing imperfections with heated customized soldering irons or tools. After the wax is chased and approved by the artist, the piece is then advanced to "Spruing" or "Gating." The gates and sprues are also made of wax. They form the channels through which the melted bronze will travel to the artwork.

"Vents" (thin wax sticks) and "Gates" (thicker wax sticks) are affixed to the wax reproduction with heated tools. Later in the casting process, the space occupied by sprues or gates become runways through which the metal flows and trapped gas escapes. Distribution of the bronze, low turbulence, ventilation and shrinkage are important considerations in the science of gating and spruing.

Investing

Around 20 Lamps Are Cast Together A Close View of Investment Opening

"Investment" is the process of building a rock-hard like shell around the wax sculpture. Later in the process, when the wax has been melted out, the investment will serve as a mold for the molten bronze. For most of history, an investment consisting of plaster, sand and water was used to accomplish this task

The technique begins by dipping the gated wax into vats of slurry followed immediately by a bath of sand. This process builds a very thin wall of silica around the wax. When repeated approximately 9 times, allowing for dry times in between dips, a hard shell about ½" thick forms around the wax.

To invest by the solid plaster method, tarpaper is loosely wrapped around the wax reproduction in the shape of a cylinder. The enclosed space surrounding the wax is then filled with a wet plaster/sand mixture. When the plaster hardens, the tarpaper is removed and a solid plaster investment is ready for "de-wax."

The wax is a "positive" which must disappear in order to create a cavity or "negative" for the bronze to fill. Thus the phrase "lost wax casting" comes from the process of the wax being melted or "lost" from the shell. Plaster invested shells are de-waxed in a kiln.

The Pour

During the pour the shell mold receives the bronze.

The Pour

A huge graphite crucible, fired by a furnace, is filled with bronze ingots that are melted. The metal begins to melt at 1700°F. Bronze "seizes" (stops flowing) when confronted with cold, which might occur if molten bronze was poured into a room temperature shell; therefore at the same time the bronze is being blasted by a natural gas furnace, the ceramic shell is heated in a kiln to approximately 1100°F.

When the Dance of the Pour begins, the crucible is lifted by a crane out of the gas furnace. At the same time, the glowing shells are brought out of the kiln to the pour area. Two artisans operate the crane which holds the crucible in a "jacket." The artisan with the controls is the "lead pour," the artisan maintaining the crucible balance is known as the "deadman." A third member of the pour team pushes away dross and slag on the surface of the molten bronze.

The entire pour is very fast and very precise; one crucible of bronze holds 400 lbs. and can fill one or two large shells or ten or more small shells. The first pieces poured are those with thin walls and intricate details; requiring hot, fluid bronze to move throughout the channel system.

Divesting

Once the bronze has hardened each investment is broken open to reveal the piece inside. Each piece must be meticulously cleaned of any residue by sand-blasting.

Metal Chasing & Finishing

Like wax chasing, bronze must also be chased or cleaned to address the slight imperfections that may result from the casting or shell building process. On larger sculptures, where assembly of cast sections is required, chasing is essential to take down weld line formed by the joining of two planes.

Metal chasing usually starts with large electric or pneumatic grinders to remove the bulk of the unwanted metal. Then, more refined and smaller tools such as die and pencil grinders are used to re-create the artist's subtle surface texture.

The artist " charles moore" inspects the rough pieces before the chasing begins.		The castings require countless hours of chasing before they recognizable as the lamp parts that make up the beautiful works of art that are the finished product.

PATINA

Patination is enhancement of 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 its own proprietary (and carefully guarded) patinas that result from a carefully orchestrated blend of different chemicals, pigments and application technique. A wide range of colors, both transparent and opaque are available to the experienced patineur.

The final step is putting a thin coat of clear wax over the bronze to enhance and preserve the patina.

The artist is seen observing the unfinished casting before they receive the patination process. All the colors that are attributed to the beauty of these bronzes are created by the chemical reaction of the metal coloring agents. Every piece must pass the inspection of the watchful eye of the master artist.