Research on the Water Loss Characteristics of Ivory at Sanxingdui Site Based on X-ray Computed Tomography

The Sanxingdui site, containing the world's largest Bronze Age ivory collection, provides critical insights into ancient Shu's trade networks and paleoenvironment. However, water loss in these waterlogged ivories causes structural damage through delamination and dentin degradation. In this study, we utilized X-ray computed tomography (X-CT) to non-destructively and dynamically monitor the water loss process of four ivories from the K7 sacrificial pit at Sanxingdui site under different temperatures and humidity (25°C and 50% RH; 5°C and 90% RH) and preservation methods (exposed, wrapped). Through three-dimensional model reconstruction and quantitative pore analysis, combined with the mechanical properties simulation of VG Studio Max software, the evolution of internal pore expansion and stress in ivory during the water loss process was revealed. The results show that the combination of low temperature and high humidity (5°C, 90% RH) when wrapped can significantly inhibit the evaporation rate of water (water loss rate <5%). Additionally, the pore structure is more stable, with the variation rates of peak von Mises equivalent stress, maximum shear stress and maximum principal stress at 103d reduced by about 31%, 36% and 166%, respectively, compared with those of the exposed group at 25°C and 50% RH. Correlation analysis further confirmed that the water loss rate was strongly and positively correlated with the porosity and the accumulation of each stress. This study established an X-CT-based multi-parameter evaluation system for ivory deterioration, which provided a theoretical foundation for implementing low-temperature, high-humidity wrapped conservation measures for waterlogged and deteriorated ivories unearthed from the Sanxingdui site.