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One question that I get asked a lot is "Why bronze?" The best way for me to answer is by explaining the process. I like to think of it as the ultimate way to make an idea last forever. how bronze is cast Bronze casting has roots that stretch back thousands of years, and the main reason why we can tell is because the sculptures are still around to tell the story. It’s only right, then, that the process of making something so enduring be an art in itself. As with the ancient sculptures that attest to this truth, the process has remained virtually unchanged since the first piece was cast a few thousand years B.C. The method known as "lost wax" casting has many steps between start and finish. The first step is making a rubber mold of the original clay piece. A layer of a polyurethane or silicone rubber is applied to the original. When the rubber dries, a layer of reinforced plaster is smoothed over the rubber to allow it to keep its shape. Once the plaster is dry, the original is removed from the rubber, and the initial mold is ready. This next step involves creating a wax "positive" out of the rubber mold "negative". Melted wax is poured inside the mold and slushed around to coat the inside of the mold evenly and completely. After one layer dries, another layer of wax is applied, slightly cooler so as not to melt the layer underneath. This is usually repeated three times, or until the wax wall is about 3/16 of an inch thick. Once the last layer is dry, the mold is opened and the rubber is peeled from the wax. The wax positive that results from step two then becomes subject to "chasing", which is the careful process of joining the wax pieces, if necessary, and erasing any seam lines or imperfections with the aid of heated tools. It is important that the integrity of the original be preserved at this stage. Thin wax sticks known as "vents" and thick wax sticks known as "gates" are fixed to the wax positive using the same tools as in the chasing process. Once it’s time for the bronze to be poured later on, the vents and gates will be the pathways through which the molten bronze will flow and any trapped gas will escape. This process is called "spruing" or "gating". Once the vents and gates are on, the wax positive goes through the investing process. In the more modern ceramic shell technique, the wax is dipped first into a slurry, then into a bath of sand. This creates a thin silica wall around the wax, and when repeated several times, a solid shell about a half-inch thick is formed. This shell will be the mold for the bronze when the wax is melted out. Molten bronze needs to stay at a consistent temperature when being poured. So, when the wax is melted out, the shell needs to remain heated until the very moment the bronze is ready to pour. Bronze ingots are heated in a crucible, and begin to melt at around 1700 degrees Fahrenheit. The glowing shells are removed from the kiln, and the liquid bronze is the poured immediately inside. The bronze is cool within an hour or so, at which point the shell can then be removed from the metal. This process is called "devesting", and requires a great degree of strength, skill, and, of course, the right tools. Power chisels and hammers are used to break the investment free of the newly solid bronze. Any gates or sprues also need to be removed, and a high-intensity electric arc is the right tool for that job, as it isn’t intimidated by the fortitude of the hard metal. Finally, any remaining investment particles are blown away by a sandblaster, and the piece then is ready for the next round of treatment in the metal shop. As with the wax, the bronze also needs "chasing" to remove any seam lines or imperfections. Larger pieces may require an engineer to design an internal structure to support the bronze so that the final piece can withstand anything that Mother Nature throws its way, such as earthquakes or fierce winds. The final touch is to apply what is known as patina, or the coloration of the piece. The colors are produced by applying chemical compounds that react with the bronze itself, bringing on the reds, yellows, greens, blacks, and golds, among others, that make the piece complete. A coat of wax is applied to preserve the patina, and, fitted onto a proper base, the artwork is ready for display. When you make an investment like purchasing bronze sculpture, it is important to know how the bronze should be cared for. You want to be certain that the piece's original beauty maintains its brilliance over time. Anyone who goes home with one of my creations is always apprised of this; it's a lot less complicated than you may think, especially since forever is a long time. caring for bronze To maintain the beauty of your bronze, it is important to never use household cleansers. Use a soft, dry cloth or a soft-bristled paintbrush to remove dust and debris. At least once a year, apply a thin coat of caranuba or beeswax-based paste wax (we recommend Trewax™ or Johnson’s Paste Wax™ , found at most hardware stores) using a soft-bristled paintbrush. Since the wax dries quickly, use a soft, dry cloth to buff a few minutes after applying the wax. Following these easy steps will ensure that future generations will see the bronze the way you do today. |
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