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Bronze Making Process
The Lost Wax Method
Seven distinct steps are required to
produce each Big Bronze sculpture:
Step 1: Making
A Mold From an Original Sculpture
This
step is the most critical. Artisans begin by completely covering an original
sculpture with specially formulated silicone or latex to capture every nuance
of the original sculpture. Once completed, the coating is allowed to set. It
is reinforced with a fiberglass shell, producing a strong, rigid, lightweight
mold. After setting, the mold is cut in half to remove the original sculpture
and sectioned into pieces to facilitate the remaining steps in the casting
process.
Step
2: Making a Wax Likeness From the Mold
A
thin coating of wax is hand painted onto the inside of each piece of the
sectioned mold. This is done to ensure that the wax completely captures every
nuance of the mold. After setting, individual pieces are assembled into the
major sections of the mold; e.g., base, torso, extremities, etc. Molten wax is
poured into the assembled molds, which are rotated throughout the process to
allow wax to build up on the “primer coating”. The process is continued until
the wax reaches a uniform thickness of roughly 3/8” in all areas. After the
wax has cooled, the latex and silicone outer shell is removed from each
section, revealing exact wax likenesses of the original sculpture. Artisans
buff and finish them, removing any imperfections arising the molding process.
Step 3: Making a Casting Mold From the Wax Likeness
The wax likenesses are each dipped into a mixture of plaster and sand. This process is repeated several times using increasingly course sand and plaster mixtures. Each layer must be allowed to dry before additional layers can be applied. After several layers are applied and allowed to set, a thick, a rigid clay shell is formed around the wax likeness. Often referred to as “investment casting”, the clay shell, once complete, is made ready for bronze casting by artisans who apply runners and vents to the shell to permit molten bronze to enter the shell and hot gases and excess metal to escape.
Step 4: “Burn Out” – Losing the Wax
The clay shells, which have now been allowed to harden around the wax likenesses, are placed upside down in a kiln and baked at high temperatures. High temperature baking hardens the clay shells into bronze-ready molds and at the same time melts away the internal wax likenesses, giving rise to the term “Lost Wax”. The melted wax flows from the casts through runners and vents, resulting in hollowed, fire-hardened clay molds, now ready for bronze casting.
Step 5: Bronze Casting
Molten bronze is immediately poured into the hardened clay casts and allowed to cool. Once cooled, the outer clay shell is carefully chipped away from each section by hand, revealing the cast bronze figures, now ready for final assembly and finishing.
Step 6: Assembling the Sections and Finishing the Sculpture
Artisans carefully and painstakingly reassemble sections of the sculpture and finish the seams and rough edges to produce a flawless finished product, ready for coloration and patina.
Step 7: Finishing and Coloring the Sculpture
The finished sculpture is finely detailed and hand polished prior to coloration and accenting. Artists apply chemicals, pigments and heat by hand to produce the striking visual beauty and extraordinary coloration that is an essential element bringing to life every Big Bronze sculpture.
Lost Wax casting, or cire-perdue, is the
traditional method of bronze casting. First used roughly 4,000 years ago to
produce unsurpassed quality and detail in bronze sculpting, it continues to be
recognized as the most precise metal casting process in existence. Virtually
unchanged since its inception, Lost Wax casting has been used by the
Egyptians, Greeks, Africans, Masters of the Italian Renaissance and other
artisans throughout history to cast superbly detailed bronze sculptures.
Although modern tools and methods have improved the process, it remains
expensive and time-consuming, requiring many hours of effort by skilled
artisans to produce the magnificent, richly detailed sculptures proudly
offered by Big Bronze at a fraction of the price typically paid for life-size
bronze sculpture. The Lost Wax process begins with an original sculpture, a
precise copy of which is cast into a mold, which is then used to produce an
exact likeness of the original.
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