Research on the Glass Beads from the Nanhai I Shipwreck: A Potash-lead Glass Bead Technological Tradition Originating from Han Dynasty Lingnan

To gain deeper insights into the manufacturing techniques and raw material sources of the glass beads collected from the Nanhai I shipwreck dating from Southern Song Dynasty, a comprehensive analysis was conducted on three typical types of beads using digital microscopy, X-ray micro-computed tomography (Micro-CT), micro X-ray fluorescence spectrometry (µ-XRF), laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) and micro-Raman spectroscopy. The results indicate that these beads are typical Chinese potash-lead and lead silicate glasses, manufactured primarily using the coiling technique. The opaque yellow coloration was obtained with the use of lead stannate (lead-tin yellow type II) as both a colorant and opacifier. The black glass beads also contain high levels of tin, while those with orange interior was colored by the combined use of Cu ₂ O and CuO. The black beads exhibit signs of weathering from the presence of such corrosion products as Pb ₂ CO ₃ Cl ₂ , PbSO ₄ , and 2PbCO ₃ ·Pb(OH) ₂ . The technological lineage of these potash-lead beads is discussed below from the perspectives of their compositional system and the nature of the opacifiers that were used, linking them to Han Dynasty potash-lead glass from Lingnan. Based on the results of trace element and lead isotope analysis, the provenance of the raw material used to these glass beads was also investigated.