Non-invasive characterization of the painting Saint John the Evangelist by means spectroscopic methods

In this work, the pigments and ground layers of the Saint John the Evangelist painting were analyzed using the techniques of computed radiography, X-ray fluorescence (XRF), and micro-Raman spectroscopy. The painting was purchased by a collector at auction as a 19th-century work of art of unknown authorship. XRF analyzes were performed with a voltage of 40 kV, current of 50 µA, and acquisition time of 60 s. Micro-Raman spectroscopy measurements of a black fragment sample were performed with the Thermo Scientific – DXR2 Raman microscope equipment. The sample was excited by the adjusted 785 nm laser source with a power of 4 mW, focused on the sample using a 100x objective. It was possible to characterize the pigments used in the painting of São João Evangelista as Lead White, Vermilion, Carbon Black, and Ocher. No areas of repainting and modern pigments were identified that could suggest any type of intervention.