Temporary consolidation and excavation of artifacts at waterlogged archaeological sites

Ensuring the preservation of fragile artifacts from waterlogged archaeological sites demands the advancement of extraction techniques that uphold both safety and the integrity of historical data. Conventionally employed extraction materials are predominantly applicable to sites exhibiting high soil stability and low moisture content, whereas the recovery of artifacts from waterlogged contexts remains technically challenging. This study explores low-acyl gellan gum as a temporary solidification material for waterlogged archaeological relics, enhancing its efficacy through ionic cross-linking methodologies. The results show that by meticulously regulating the species and concentration of cations-specifically Na⁺, Mg²⁺, Ca²⁺, or Al³⁺- an improvement in gelling strength can be attained within an optimum range. The gel strength improved with the increase of ion valence, but adding Al³⁺ results in local gel aggregation. By adding 3.0 wt% of CaCl₂, low-acyl gellan gum can form a transparent, stable gel with a compressive strength amplified to 0.11 MPa. In addition, the temporary consolidation and extraction experiment under laboratory conditions shows that Ca²⁺ cross-linked gellan gum can effectively carry out temporary solidification and safe extraction of multiple artifacts at waterlogged archaeological sites. This innovation presents a simplified yet potent strategy for excavating fragile artifacts.