How it began
Mehrgarh, in Balochistan in present-day Pakistan, was a center of innovation from Neolithic times. A small wheel-shaped copper amulet found there in the 1980s is about 6,000 years old. Its shape shows it was made by lost-wax casting, and a 2016 study in Nature Communications identified it as the oldest known artifact made by that method.
How it works
The maker shapes a model in a material that melts at low temperature, such as beeswax. The model is covered in clay, which is heated so the wax runs out and then baked. Molten metal is poured into the hollow mold, and the mold is broken to release the object. At Mehrgarh the metal was very pure copper, and the study found that it had absorbed a small amount of oxygen as it solidified.
What lasted
Lost-wax casting is the earliest known technique of precision casting. The researchers describe lost-wax casting as a fundamental invention and as the technique that led to art foundry. The archaeology.wiki report on the study notes that the method is still in use today. The study authors wrote that the amulet gives a better understanding of how the invention came about.
Where it stands today
The amulet is now almost entirely copper oxide. In 2016 a team from the CNRS, the French Ministry of Culture and the SOLEIL synchrotron used a new photoluminescence imaging method to see its hidden internal structure and reconstruct how it was cast, including the purity of the copper and the temperatures of melting and solidification.
