Mirrors of the deep: a scientific investigation of southern song handled bronze mirrors from the Nanhai No. Ⅰ Shipwreck

The scientific investigation of handled bronze mirrors recovered from the Nanhai No. Ⅰ shipwreck offers new insights into their production techniques, alloy compositions, and cultural significance during the Southern Song Dynasty (1127–1279 AD). They include 6 six-lobed mirrors, 4 nearly circular mirrors, and 14 lozenge-shaped mirrors each adorned with a single dragon motif. Using micro X-ray fluorescence (µXRF) and MC-ICP-MS, we analyzed the alloy ratios and lead isotope characteristics of these artifacts. Alloy composition analysis reveals that copper-tin-lead ratios in these Southern Song mirrors are consistent with earlier findings, showing higher lead content than previous mirrors but lower than Song coins. This indicates intentional use of advanced metallurgy to balance durability, efficiency, and design stability. Lead isotope results indicate that the lead sources for these handled mirrors can be categorized into at least two distinct groups, corresponding to different types of mirrors. However, none of these sources are from Jiangxi, which was the primary lead supplier during the early Southern Song period. The dragon-motif mirrors and those inscribed with the Huzhou mark exhibit similar alloy compositions and lead isotope characteristics, indicating, supported by stylistic evidence, that they were likely produced by the same manufacturer. Contextualized within the historical literature, these findings suggest that the bronze mirrors were made from legally sourced metals rather than recycled materials and were exported abroad with official sanction. These findings contribute to a deeper understanding of Southern Song metallurgical practices and trade, highlighting the sophisticated techniques employed by artisans and the regulatory frameworks governing the production and distribution of these artifacts.