Identification, Removal, and Preventive Protection Against Mold Contamination on Historical Photographic Negatives from the Xi’an Beilin Museum

The Xi’an Beilin Museum preserves a large collection of archeological photographic negatives and films dating from the 1950s to the early 1980s. These images document significant archeological discoveries, including Tang dynasty imperial tomb murals, the excavation of the terracotta warriors, and various historical grottoes and stone carvings. As unique visual records of cultural heritage, these materials provide valuable references for studying environmental deterioration processes and for guiding conservation and restoration practices. However, long-term storage under uncontrolled environmental conditions has resulted in severe degradation of the negatives, including mold contamination, emulsion layer powdering, deformation, and partial detachment. Among these deterioration phenomena, microbial growth is particularly destructive because fungal hyphae cause light scattering and image obscuration, preventing scanning and digital archiving. In this study, mold species present on the negatives were isolated and identified using morphological observation and ITS rDNA sequence analysis. Based on the characteristics of the microbial contamination, targeted removal and restoration treatments were applied to recover the original image information. Furthermore, preventive protection strategies were implemented through the development of antifungal storage materials and protective containers. The results establish an integrated conservation approach combining microbial identification, restoration treatment, risk elimination, and preventive protection, providing a scientific basis for the long-term preservation of historical photographic archives.