Advanced methods for the analysis of Roman wall paintings: elemental and molecular detection by means of synchrotron FT-IR and SEM micro-imaging spectroscopy

The reconstruction of Roman decorative apparatus from delocalized fragments is an arduous challenge for the archaeologists. An archaeometric approach may integrate the archaeological analyses, based on the stylistic observations, improving the ability to merge adjacent fragments, especially in the absence of distinctive ornamental elements. In this work, the capacity of reflection FT-IR spectroscopy combined with chemometric tools to identify groups of fragments that have similar chemical composition of the pictorial layers is tested. Synchrotron radiation-based Fourier transform infrared (SR-FTIR) microspectroscopy coupled with scanning electron microscopy (SEM) and energy-dispersive X-ray micro-analysis (EDX) performed on cross section were used to enhance the performance of conventional FT-IR technique and to localize micrometric-size compounds. The chemometric approach proposed in this work turns out to be a powerful way to discriminate pictorial layers with similar chemical composition, by the identification of different compounds. The use of SR source has permitted to improve the lateral resolution and to discriminate neighboring micro-compounds, such as quartz and cuprorivaite in Egyptian blue pigments.