Much has changed in the thousands of years since humans started making objects out of metal. Whether it’s advancements in materials or new techniques, ancient metalworkers would have a hard time fathoming how different the process to make most metal items is today. However, a new look at an ancient amulet reveals that some techniques never go out of style.
Back in the 1980s, archaeologists working at a Neolithic settlement in modern-day Pakistan uncovered a 6,000-year-old copper amulet. It looked like a six-spoked wheel, and had been corroded and oxidized by thousands of years of age. However, this simple amulet is one of the oldest-known examples of an object made by lost-wax casting—a manufacturing technique still used today, Sarah Kaplan reports for The Washington Post.
Earlier methods for molding metal usually involved making a negative cast and pouring molten metal into it. While it has the benefit of being able to reuse the mold once the metal cools and the item can be removed, it can’t make very complex objects. Lost-wax casting, on the other hand, is different beast. By making a version of the desired object out of wax, building a mold around that and then melting the wax, a metalworker can make things that are much more complicated and structurally-sound even if the mold has to be destroyed at the end of the process, Michael Koziol reports for Popular Science.
Figuring out that this simple-seeming amulet was made with lost-wax casting took some specialized equipment. For a new study published in Nature Communications, researchers using a synchrotron bombarded the object with high-powered beams of light that allowed them to peer inside and take a look at its interior structures. What they found were numerous, microscopic copper bristles that may have been the result of oxygen impurities introduced to the object during the casting process, Kaplan reports.
"Although it has been corroded, although it has been buried in the ground for thousands of years, [it provides] a unique testimony of the civilization at the time," Mathieu Thoury of the French National Center of Scientific Research, who led the research, tells Eva Botkin-Kowacki for The Christian Science Monitor.
Thoury says the copper bristles and the amulet’s lopsided shape suggest that whoever was making it was just learning how to use the lost-wax casting technique. The use of pure copper is also evidence that whoever was creating the amulet was still trying to figure out early metalworking, as pure copper is much harder to work with than copper alloys created later on, Botkin-Kowacki reports.
“It is not the most beautiful object, but still it holds so much history,” Thoury tells Kaplan. “It shows how the metalworkers at the time were so innovative and wanted to optimize and improve the technique.”
Lost-wax casting hasn’t entirely gone away, either—much more refined versions of the technique are still used in manufacturing sensitive scientific equipment. While the method has come a long ways, this early example shows just how early on humans were trying to find better ways of making complicated objects.