From a Point to the Grid: In Situ Raman Spectroscopy of Selected Paintings From the Collection of the National Gallery-Alexandros Soutsos Museum, Athens, Greece

Abstract

Three paintings of Symeon Savvidis, one of Francesco Pige and one from Andreas Kriezis belonging to the permanent collection of the National Gallery-Alexandros Soutsos Museum located in Athens, Greece, were analysed in situ, during the museum's opening hours, by Raman spectroscopy, handheld x-ray fluorescence (hXRF) and hyperspectral imaging (UV-Vis- NIR HSI). Raman spectroscopy point analysis, performed on multiple points on the surface of the paintings, revealed the materials used by the artists. Additionally, micro-Raman maps were obtained from selected areas, for the distribution of the pigments to be revealed. This is one of the first testimonies of in situ Raman mapping of easel paintings, performed in a museum, during opening hours. Challenges on maintaining the focusing during the acquisition of the Raman maps are also underlined. Materials frequently identified via Raman spectroscopy were lead white (2PbCO3·Pb (OH)2), vermillion (HgS), ultramarine blue (Na6-10Al6 Si6O24S2-4), Prussian blue (KFeIII[FeII (CN)6]·xH2O or Fe4 III[FeII (CN)6]3·xH2O) with other components found complementing the palette of the artists (e.g., chrome yellow (PbCrO4), chrome orange (PbCrO4·Pb(OH)2, carbon-based black (C)). Sporadically and in different paintings, haematite (α-Fe2O3), strontium yellow (SrCrO4) and barium sulfate (BaSO4) were characterized. hXRF and UV-Vis- NIR HSI supported the information retrieved by both Raman instruments.