Step One I sculpt in a relatively soft, oil-based clay, which never hardens. I prefer a softer, more malleable material so that I can achieve the fluidity of movement and flow that I desire in my work. The clay is applied to an armature that I build upon a plywood base. For table-top-sized pieces, I build the armature using plumber’s fixtures, aluminum wire, and electrician’s tape. The aluminum wire, in varying gauges, is cut, bent and taped into a skeletal understructure designed to shape the sculpture and also to provide support and hold the clay intact in the shape of the finished piece. The clay is applied and formed over the armature, using primarily my fingers and various sculpting tools made from wood, metal and/or wire. For detailed work, I often use “recycled” dental tools. The completed, original “clay” sculpture is identical to the completed bronze casting, except that it is created in clay and is still attached to the armature. Step Two At the foundry, the clay sculpture is photographed and measured in detail for reference purposes at various stages during the casting process. Most of the clay sculptures are then cut into pieces for molding purposes. The “flow” of the metal through the mold determines the number, shape and size of each segment into which the clay is cut. A silicon rubber mixture is then brushed or otherwise placed on the outside surfaces of the clay sculpture segments to form a flexible mold that will duplicate all of the sculpture’s intricate textures and shapes. The molding compounds in current use can create up to 500 or more castings of consistent quality. Each mold segment, while still adhering to the clay sculpture segment, is then encased within a “mother mold” of either plaster or fiberglass. This mother mold helps retain the shape of the piece as castings are made since the silicon rubber remains quite flexible. Step Three Once the silicon rubber mold is removed from the clay sculpture wax and its interior surfaces are cleaned of any remaining clay particles, heated wax can be poured into and around the interior of the rubber mold. This wax hardens into a wax “positive” of the sculpture and is poured to the thickness desired for the final bronze casting. When hardened and cooled, these wax positives of all segments of the sculpture are then “chased” by artisans to match the original clay sculpture. Bubbles, mold lines and other irregularities are chased (tooled) out of the wax positive. These wax castings of the original sculpture segments are then attached by means of hot wax to a wax “funnel”. Strips of wax called sprues (wax connections—that will ultimately serve as “hoses or straws”) are next attached to connect the sculpture segments and the wax funnel. The concept is ultimately to allow the flow of the molten bronze into the funnel and through the sprues into each segment of the sculpture while also permitting air to flow out of these mold segments as the bronze is invested. When fully connected, each of these “sculpture trees” is then repeatedly dipped into a liquid slurry mix and then into fine grain silica sand. Between dippings, the tree is cooled and air-dried to remove any moisture or pockets of air. After many dipping and drying periods, and when completely dry, the wax tree is baked in an oven, with the funnel side down. The heat melts the wax, which runs down through the sprues and the funnel into a catch-pan. The hardened slurry mix has now become a ceramic shell “mold”. This ceramic shell mold that originally encased the inside and outside of each of the wax segments now is a hollow mold whose purpose is to make a single bronze casting. Step Four Bronze ingots are next heated to 2,000 plus degrees for melting into liquid bronze. While this is being done, the ceramic shell molds are placed funnel-side up in a metal rack, supported by a metal grid, and are also heated to an identical temperature as the bronze ingots. When both have attained the correct temperature, the bronze is poured into the funnel. The liquefied bronze runs throughout the ceramic mold, following the original sprue lines, to create the final bronze casting. When cooled sufficiently, the ceramic shell is broken off the bronze casting, and the metal is sand-blasted to remove the last of the shell fragments. Step Five Using acetylene torches, the sprue and funnel castings are then cut off of the bronze segments of the final sculpture. The sculpture segments are welded into place, following the measurements and photographs taken and “markings” applied when the original clay sculpture was molded, to create the final bronze sculpture. Metal “chasing” with power tools then removes any mold or casting lines, air bubbles, or other imperfections created during the casting process. The chasing is complete when the bronze casting looks identical to the original clay sculpture. A final sandblasting with silica (a finely ground glass) completes the cleaning and finishing process and removes any remaining segments of the ceramic shell. Step Six The bronze sculpture is now ready for the final patina (coloration) process. Depending upon the ultimate color and finish desired by the artist or the purchaser, one or more chemicals are applied to the heated metal. These chemicals may be dipped, poured, sprayed with high or low intensity pressure, or painted onto the metal. Varying patterning and colorations from the same chemical occur depending upon how the chemical is applied and to what temperature the bronze is heated during the application. Frequently, several applications of the same chemical may be applied to darken the tone, or a fine-grain silica sand may be rubbed onto the metal to lighten the color. Fine-art bronze is about 85 percent copper. The copper is what interacts with the metals to create the ultimate color. The chemical soaks into the metal’s pores and actually changes its composition, creating a transparent, living color to the sculpture. If colors other than those attainable through chemicals are desired, pigments may also be painted directly onto the metal. Pigments create an opaque coloration since they “lay” on top of the metal, so I usually recommend that any pigment application be done in a thin glaze, and that a portion of the resulting color is “wiped” back to create a semblence of translucency. Once patina is complete, a coating of high quality Carnuba wax is applied with a brush and melted into the sculpture while the metal is still hot. This seals the pores and stops the chemical process to “fix” the final color and finish. If pigment is used, a spray fixative is used rather than wax. Step Seven The finished sculpture is then cooled, hand or machine buffed to the desired degree of shine, and attached to its base for display. Ongoing and future care of a bronze sculpture is simple. Keep any and all chemicals away from the bronze itself, including dusting, shining and waxing sprays, cloths and other such compounds. For dusting use only a soft, untreated cotton cloth. Depending upon the site location for the bronze and variables such as sun, water, and salt-air, once or twice a year the bronze metal may be touched up with a high-grade Carnuba wax to retain a protective coating on the metal’s surface. I normally recommend using “neutral” Kiwi paste shoe wax (not the liquid, but the paste wax contained in the flat metal disk container). It is a very high grade Carnuba paste wax, has no dyes, and is easily attainable. This has been a very brief overview of the bronze casting process. Should you have an opportunity to visit an actual fine-art bronze foundry, take the opportunity to request a tour. Most will oblige, and seeing the “magic” of bronze casting is wonderful! There is something special is being a part of and/or witnessing a process that is thousands of years old! Watching a sculpture “birthed”—seeing it come to life when chemicals are applied—is a miracle to witness. Enjoy! | Equine | | Animals Domestic | | Animals Wildlife | | Figurative | | Children | | Western | | Native American | | Lifesize&Monumental | | Work-in-Progress | © Copyright Celene Greene 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005 All Rights Reserved Web Design~Hosting Sculpture Marketing Services Fine Art West Sculpture Collector