Identification of pigments on Byzantine wall paintings from Crete (14th century AD) using non-invasive Fiber Optics Diffuse Reflectance Spectroscopy (FORS)

Abstract

In this paper a combined analytical methodology was employed aiming to explore the potential of the non-invasive Fiber Optics Diffuse Reflectance Spectroscopy (FORS) technique for Byzantine wall painting pigments' characterization, as well as to assess the reliability of analytical information comparing the results with detailed spectral analyses obtained by advanced laboratory techniques such as Environmental Scanning Electron Microscopy with Energy Dispersive X-Ray Analysis (ESEM-EDX), Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR) and micro-Raman Spectroscopy. Byzantine wall paintings (14th Century) decorating two Churches located in the settlements of Patsos and Meronas at Amari, Crete, were investigated in a first systematic research effort to study the mural painting pigments and techniques employed on the island during this period. Micro-sampling was allowed for laboratory analyses only from the Patsos Church's murals. The results obtained from the various spectroscopic methods employed confirmed the identification of pigments (red/yellow ochres, cinnabar, green earth, etc) and that the mixed fresco-secco technique was used in these paintings. In order to characterize the Meronas murals, a comparative study was performed between the acquired FORS spectra of both Churches and the laboratory analyses results. The data obtained confirmed the effectiveness of FORS technique for wall painting pigments' identification, offering key advantages such as instrument mobility and rapid data collection which are of utmost significance in the field of archaeological research.The present work provides detailed information on the structure of pigments and the interpretation of the FTIR spectra by assigning characteristic vibrational modes in these spectra and the electronic transitions of the VIS-NIR spectra, which would be of great value as a reference for other FTIR and FORS researchers in this field.