INSPIRED BRONZE, INC. creates all of its castings via the LOST WAX CASTING PROCESS. Lost wax casting is a process by which A WAX PATTERN is TRANSFORMED INTO METAL.
FIRST, the ARTIST CREATES AN ORIGINAL ARTWORK from wax, clay and/or other material. In some cases, 3D scanning can be used to capture the original piece. Once in the computer the 3D data can be scaled up or down to create a model for the new casting. For reduced sizes, a model can be printed on a 3D printer.
A MOLD is then made of the ORIGINAL SCULPTURE. With some pieces, this can be ACCOMPLISHED by CREATING ONE MOLD for the entire piece. Generally, however the piece must be MOLDED IN PARTS. Most molds are AT LEAST TWO PIECES, and a SHIM with KEYS is placed between the two halves DURING CONSTRUCTION so that the mold can be PUT BACK TOGETHER ACCURATELY. INSPIRED BRONZE often uses FIBERGLASS to make the MOTHER MOLD. To PRESERVE the FINE DETAILS on the ORIGINAL ARTWORK’S SURFACE, an INNER MOLD is made of URETHANE or SILICONE RUBBER which is supported by the mother mold. The ORIGINAL ARTWORK is often damaged or destroyed during the MAKING OF THE MOLD.
ONCE THE MOLD IS FINISHED, MOLTEN WAX is poured into it and SWISHED AROUND until an EVEN COATING covers the ENTIRE INNER SURFACE of the mold. This must be done in SEVERAL LAYERS until the DESIRED THICKNESS is achieved. Once this is complete, the new HOLLOW WAX COPY of the ORIGINAL ARTWORK is removed from the MOLD. Each hollow wax copy is then “chased”. A HEATED METAL TOOL is used to RUB OUT ALL THE MARKS which show the PARTING LINE or FLASHING where the pieces of the MOLD CAME TOGETHER
. The wax is then DRESSED to hide any IMPERFECTIONS. The way the wax looks AT THIS STAGE is what it will look like when it is cast. WAX PIECES that were molded separately can be HEATED AND ATTACHED. REGISTRATION MARKS are used to indicate EXACTLY where they go. ONCE the WAX COPY looks just like the ORIGINAL ARTWORK, it is SPRUED with a TREE-LIKE STRUCTURE of WAX that will eventually provide PATHS for MOLTEN BRONZE to flow, while allowing AIR TO ESCAPE. The CAREFULLY PLANNED SPRUING usually begins at the top with a cup, which is ATTACHED BY WAX CYLINDERS to various points on the WAX COPY.
A SPRUED WAX COPY is dipped into a SLURRY LIQUID of SILICA, then into a SAND-LIKE STUCCO, or DRY SILICA of a controlled grain size. The SLURRY and GRIT combination is called CERAMIC SHELL MOLD MATERIAL. The shell is ALLOWED TO DRY, and the PROCESS is REPEATED until a HALF-INCH THICK or thicker dried coating COVERS THE PIECE. The BIGGER the piece, the thicker the SHELL needs to be.
The CERAMIC SHELL-COATED PIECE is placed cup-down in a KILN, whose heat HARDENS the SILICA coatings into a SHELL, and the WAX MELTS and RUNS OUT. At this point, ALL THAT REMAINS of the ORIGINAL ARTWORK is the NEGATIVE SPACE FORMALLY OCCUPIED by wax. The FEEDER, vent TUBES and cup are now HOLLOW as well.
THE SHELL is REHEATED in the KILN, then placed CUP-UPWARDS into a tub filled with sand. BRONZE is MELTED in a CRUCIBLE in a FURNACE, then POURED carefully INTO THE SHELL. If the SHELL were NOT HOT, the TEMPERATURE DIFFERENCE would SHATTER IT. The BRONZE-FILLED SHELLS are allowed to cool. The shell is then HAMMERED or SAND-BLASTED away, releasing the ROUGH BRONZE. The sprues and vents, which are FAITHFULLY RECREATED in metal, are cut off to be RECLAIMED FOR FUTURE CASTINGS.
JUST as the WAX COPY was CHASED, the BRONZE COPY is worked until the tell-tale signs of casting are REMOVED, and the SCULPTURE again LOOKS LIKE the ORIGINAL ARTWORK. Pits left by air bubbles in the MOLTEN BRONZE are filled, and the stubs of spruing FILED DOWN AND POLISHED.
THE BRONZE is then COLORED to the ARTIST’S PREFERENCE, using CHEMICALS APPLIED to carefully HEATED METAL. This COLORING is called PATINA. After the PATINA is APPLIED, several clear coats of LACQUER are applied to PROTECT THE PATINA from change, then a COATING OF WAX is applied to create the TRADITIONAL LOOK and feel of a BRONZE SCULPTURE.
Content provided by Inspired Bronze: www.inspiredbronze.com