A novel method of temporary solidification and extraction of underwater fragile relics in their original state

Abstract Fragile cultural relics at underwater archaeological sites are difficult to preserve in situ over long time periods due to the effects of a complex and constantly changing surrounding environment. Thus, extracting the relics from water and preserving them in a controllable environment is of primary importance. In this paper, the technology of temporary reinforcement and extraction of underwater fragile relics with veratraldehyde followed by a process of secondary temporary reinforcement using polyethylene glycol (PEG) was studied. After investigating the melting temperature and permeability of PEGs with different molecular weights, we found that PEG-3000 is an excellent candidate as the secondary reinforcing agent for the extracted relics. In the laboratory, combined with veratraldehyde and polypropylene-fiber cloth as temporary underwater strengthening materials, and selected dispersed beaded jewelry and a broken three-dimensional crock as our research subject, we carried out an entire retrieval process—temporary stabilization and secondary temporary reinforcement, to systematically evaluate the technological aspects of safely excavating fragile underwater relics in the original state. After being extracted from water and subjected to secondary temporary reinforcement using PEG-3000, the beaded jewelry and broken crock retained their underwater shape and arrangement completely. The use of secondary reinforcing agent prevents the removal process of veratraldehyde and enclosed sediment from affecting the state of the relics.