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.
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.
