Reversible Organic Coatings for On-Site Comprehensive Emergency Protection during Archaeological Excavations

Once excavated, cultural relics face immediate threats from oxidation, water loss, mold growth, etc., which are caused due to severe environmental changes. Covering with plastic films, spraying water, or applying biocides followed by mechanical polish are common conservation practices, which are effective to some extent, but with obvious side effects. Menthol, often used as volatile binding material (VBM) in heritage conservation, has been proved to be safe to conservators and cultural relics and can be removed easily via sublimation with no residue. In this study, the possibility of using menthol coatings as a reversible environmental barrier to protect cultural relics during excavation is examined. Laboratory results show that menthol coating has an excellent ability to prevent oxygen and water molecules from passing through it, to stop various fungal growths and cut off radiation below 300 nm. On-site antifungal applications on a mural tomb of the Tang Dynasty, located in the north of Xi'an Xianyang International Airport, provided satisfactory results. Laboratory and field results show that menthol coating has high potential of being used for the emergency protection of relics against sudden environmental changes during excavation.