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Breaking the mould

Breaking the mould

作者:兀官喁圆  时间:2019-03-07 12:19:20  人气:

By Nell Boyce in Washington DC SCULPTORS can now create works of art in bronze without having to make complex moulds that must be filled with the liquid metal. The secret is a new low-temperature casting technique that also allows sculptors to use pottery kilns rather than industrial foundry equipment to make pieces. Rand German, a materials scientist at Pennsylvania State University in State College, got the idea for the technique two years ago when he commissioned a large bronze from local sculptor Mark Pilato. He was astonished when Pilato gave him a 110-page book detailing each step of the complicated bronze casting process. “Has an engineer looked at this process in the last several hundred years?” German asked. Traditionally, sculptors carve their piece in wood or clay. They then make a mould of the carving and fill it with wax. The wax cast has to be covered with many ceramic coats, and you have to wait many hours between coats. Finally, the wax is melted and poured out of the ceramic mould, which foundries fill with molten bronze at 1200 °C. German suggested that Pilato abandon molten bronze and instead make sculptures out of powdered metal mixed with wax, a variation of an industrial process called sintering. Factories routinely make metal items such as bearings by filling a mould with powdered metal, compacting it and heating it until the solid pieces of metal fuse. Working in his garage, Pilato worked out the best mixture of various bronze powders and waxes. He would pour a mixture into a plastic mould and wait for it to harden, or simply carve a lump of a mixture. Then he would fire the piece at 800 °C, so that the wax melted away and the solid bronze pieces fused. “We were getting cracks, holes and blow-ups in the beginning,” says Pilato, but he finally found a mixture, which he’s patenting, that looks very like cast bronze and is just as strong. The new process saves time: Pilato has finished a chess set in three days that would have taken months to cast at a foundry. Phil Sumpter, a bronze sculptor in Philadelphia,