Multi-Analytical Characterization of the Materials and Manufacturing Technology of a Southern Song Dynasty Tixi Lacquer Plate from the Nanhai No. 1 Shipwreck

A rare carved lacquer (tixi) plate recovered from the Southern Song Dynasty Nanhai No. 1 shipwreck was examined to reconstruct its coating stratigraphy, raw materials, and manufacturing sequence. Detached fragments collected before conservation treatment were investigated by cross-sectional optical microscopy, micro-Raman spectroscopy, thermally assisted hydrolysis–methylation pyrolysis–gas chromatography/mass spectrometry (THM-Py-GC/MS), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), and wood-anatomical microscopy. The polished cross-section contains nine lacquer layers with a combined thickness of 387.3 μm above a heterogeneous ground, yielding ten visually distinguishable strata. Alternating dark, red, and yellow layers establish the technological basis for the carved polychrome effect. Raman bands identify cinnabar (HgS) in the red layer and orpiment (As₂S₃) in the yellow layer. THM-Py-GC/MS detected homologous alkenes, alkanes, and alkylbenzenes diagnostic of Chinese lacquer derived from Toxicodendron vernicifluum. Monocarboxylic acids were present, whereas no clear dicarboxylic-acid markers of a drying oil were observed; because the object was waterlogged and degraded, this absence is treated as a lack of positive evidence rather than proof that oil was never used. The ground is enriched in Ca and P and is therefore consistent with a bone-ash-based filler, although phase-specific confirmation remains necessary. Wood anatomy identifies the substrate as Chinese fir (Cunninghamia lanceolata, Cupressaceae). Together, the results document an organic–inorganic multilayer coating system and provide material evidence for Southern Song carved-lacquer technology, while defining conservation risks associated with a waterlogged wooden core and light-sensitive pigments. The marine archaeological context and the support-to-surface, layer-resolved design distinguish this case from most previous studies of Song-dynasty lacquerware. Beyond technological reconstruction, the findings identify conservation priorities for waterlogged wood, the wood–ground–lacquer interface, and light-sensitive pigmented layers, and provide a transferable evidence framework for comparative research on archaeological lacquer.