Self-Shaping PVA/CMC Hydrogel for Gentle Cleaning of Harmful Patina on Bronze Relics

The removal of harmful patina is a critical step in the conservation of bronze relics. However, the uneven surfaces formed by intricate relief patterns on bronze ware make thorough cleaning a formidable challenge. To overcome the inability of traditional gel materials to conform fully to such elaborate decorations, this study proposes an in situ self-shaping hydrogel cleaning strategy. Specifically, a high-viscosity polymeric dispersion (HVPD) loaded with tetraethylenepentamine (TEPA) was prepared using sodium carboxymethyl cellulose (CMC) and poly(vinyl alcohol) (PVA) as thickeners. The self-shaping characteristics of HVPD enable complete coverage of intricate bronze patterns, while the loaded TEPA exhibits strong dissolution capacity against harmful patina, achieving targeted removal. Subsequently, the polymeric dispersion undergoes in situ physical cross-linking on the bronze surface via a freeze-thaw method, forming a mechanically enhanced hydrogel. After cleaning, the hydrogel can be completely peeled off from the bronze surface without residue, and the harmful patina on bronze relics can be gently cleaned. This approach provides an innovative solution for harmful patina removal in bronze conservation with broad application prospects.