Characterization of art materials and degradation processes in the exterior wall paintings of the main church of Rila Monastery, Bulgaria

A groundbreaking analysis of the exterior wall paintings at Rila Monastery, Bulgaria—a UNESCO World Heritage Site and the last large-scale example of Eastern Orthodox mural art—reveals significant degradation linked to atmospheric exposure. The study identified natural pigments like red ochre and green earth alongside synthetic ones such as ultramarine and vermilion, which remain stable. However, minium (lead-based pigment) has chemically transformed into black plattnerite or white lead carbonate, altering the paintings' appearance. Emerald green pigment also showed partial degradation without major color changes. The research used a multi-technique approach, including ATR-FTIR, Raman spectroscopy, and SEM-EDS, to characterize materials and decay products like gypsum and calcium oxalate. Binders confirmed the use of egg-tempera, with chemical degradation suggested by metal oxalates. Notably, the study highlights the introduction of emerald green pigment and synthetic ultramarine, diverging from traditional Byzantine practices.

Stamboliyska, B., Tapanov, S., Kovacheva, D., Atanasova-Vladimirova, S., Ranguelov, B., Yancheva, D., Velcheva, E., Stoyanov, S., Guncheva, M., Fischer, D., & Lederer, A. (2023). Characterization of art materials and degradation processes in the exterior wall paintings of the main church of Rila Monastery, Bulgaria. Vibrational Spectroscopy, 128, 103580. https://doi.org/10.1016/j.vibspec.2023.103580