Chinese texts have described brass production since the 10th century, yet until now the oldest physical evidence of brass-making in East Asia dated to the 16th century — a 600-year gap that puzzled archaeologists. New research from Guangzhou, southern China, closes that gap.

A team of researchers examined nearly 80 crucibles and fragments from a metalworking workshop near the Royal Palace of the Nanyue Kingdom, excavated between 1975 and 2007. Portable X-ray scans revealed an unusual rise in zinc in some vessels, and laboratory analysis found tiny droplets of brass trapped on the surfaces of three crucibles dated to the 9th and 10th centuries.

The chemical residues show a complete production system: fresh copper was used to make pure brass, and unleaded bronze to produce a copper-zinc-tin alloy, all through a process called cementation. The crucibles' shape and firing temperatures — lidless vessels heated above copper's melting point, around 1,980°F — closely resemble brass-making vessels from the medieval Islamic world, as does the relatively low zinc content of the brass produced.

Guangzhou was a natural conduit for such knowledge. After the Tang dynasty lost control of much of the Silk Road in the 8th century, maritime routes became China's key links to the outside world, and the city hosted large communities of Arab merchants and craftsmen. The researchers see the Islamic world as a likely source of the technology, though the study, published in Antiquity, does not prove direct transfer.

The discovery pushes the physical evidence for Chinese brass production back by 600 years and illuminates how trade routes carried not just goods but methods and skilled labor — laying the groundwork for the large-scale brass industry of the Ming dynasty.

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