Salt-induced flaking of wall paintings at the Mogao Grottoes, China

Lori Wong, Su Bomin, Xiaowei Wang, Amarilli Rava, Neville Agnew

Research output: Chapter in Book/Report/Conference proceedingConference contribution


The Mogao Grottoes, a World Heritage Site in northwest China, is known for its surviving 492 painted Buddhist cave temples. Commissioned over a thousand year period, from the fourth to the fourteenth centuries, the caves were hewn into a 1.6 km long cliff face and the wall paintings executed on earthen plasters. Situated in a remote and arid desert landscape, these painted caves have endured throughout the centuries but many have also suffered from salt-related deterioration. Repeat cycles of treatment for flaking on salt-damaged wall paintings have caused
worsening of conditions resulting in significant loss of painted plaster. A research project to study this intractable problem and to develop and implement improved treatment methods was undertaken as part of a collaboration between the Getty Conservation Institute (GCI) and the Dunhuang Academy (DA) under China’s State Administration for Cultural Heritage (SACH).

This case study looks at the activation mechanisms and deterioration processes of salt-induced flaking and highlights the development and implementation of remedial and preventive measures to prevent further loss from occurring. Topics investigated include the material composition of the paintings and plaster, previous treatments, salt identification and distribution, environmental conditions and the impact of increased humidity. Results show that past treatment of flaking wall painting with polyvinyl alcohol (PVA) and polyvinyl acetate (PVAc) created a film-like barrier that reduced permeability and trapped salts below the painted surface. This led to a build up of salts that when exposed to periods of high humidity caused disruption and powdering of the plaster from cycles of deliquescence and crystallization; the consolidated upper layer, then separated and lifted, in a new form of flaking, referred to as exfoliation. The study also aimed to improve methods of condition monitoring to better assess when change due to salt activity occurs and to implement findings from the Visitor Carrying Capacity Study for the site. This included identifying caves at risk of salt-related deterioration and closing them to visitation during periods of high humidity.
Original languageEnglish
Title of host publicationSWBSS 2017
Subtitle of host publication20-22 September 4th International Conference on Salt Weathering of Buildings and Stone Sculptures
Publication statusPublished - Sept 1 2017


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