In Situ Block Lifting Strategies for Fragile Waterlogged Archaeological Remains: A Case Study from the Nanhai No. 1 Shipwreck

Abstract Fragile remains from waterlogged and high-humidity environments often present considerable challenges for in situ recovery due to long-term degradation, reduced mechanical strength, and the need to preserve archaeological context. Block lifting can effectively recover fragile remains while preserving spatial relationships, though the choice of strategy depends on preservation conditions and field requirements. This study examines the development and application of in situ block lifting strategies during the long-term excavation of the Nanhai No. 1 shipwreck. Based on archaeological assessment and recovery requirements, three strategies were developed: direct lifting, single-material lifting, and multimaterial lifting. The multimaterial strategy integrated menthol, polyurethane bandages, plaster, and polyurethane foam, with each material performing specific functions in surface protection, conformable reinforcement, and external structural support. These strategies were applied under monitored high-humidity conditions (RH frequently exceeding 85%) to recover wooden components, fragile organic remains, and complex assemblages. The results demonstrate that condition-based selection of lifting strategies enabled safe recovery while preserving morphology and spatial relationships. The Nanhai No. 1 excavation provides practical insights into integrating archaeological assessment, material selection, and structural support during in situ recovery of fragile remains.