Investigating the Material Composition and Degradation of Wall Paintings at Müstair Monastery Using a Mobile Multi-Spectroscopic System

The conservation of cultural heritage requires advanced analytical tools to assess historic materials. In the context of the IPERION-CH project, a mobile multi-spectroscopic characterisation system for the analysis of cultural heritage materials, designated SYSPECTRAL, has been developed. This system integrates Laser-Induced Breakdown Spectroscopy (LIBS), Laser-Induced Fluorescence, Raman spectroscopy, and reflectance spectroscopy. The first application of SYSPECTRAL in a real-world setting was carried out at Müstair Monastery (UNESCO World Heritage Site since 1983) for wall paintings. In this study, stratigraphic analysis using LIBS revealed lead- and iron-based pigments in black and red hues, suggesting pigment degradation and restoration interventions. The presence of titanium in white hues indicated possible retouching. Furthermore, the presence of Egyptian blue in blue hues was identified through a combination of elemental and reflectance spectral analysis, underscoring the potential of SYSPECTRAL for heritage conservation. This approach offers comprehensive material characterization with minimal impact, a finding that is of particular significance in the context of heritage conservation. The subsequent phase of research will extend the application of SYSPECTRAL to a wider range of heritage sites, with the objective of enhancing the spectral databases and refining the analytical techniques for the purpose of improving cultural heritage conservation.