Synchrotron-based scanning macro-X-ray fluorescence applied to fragments of Roman mural paintings

Roman wall fragments dating from 2nd and 3rd centuries AD, from two sites of the Roman province of Germania Superior, near the present day towns of Wössingen (Baden-Württemberg) and Mülheim-Kärlich (Rheinland-Pfalz), were analyzed with synchrotron-based scanning macro-X-ray fluorescence (SR-MA-XRF) at the FLUO beamline (ANKA Synchrotron Radiation Facility, Karlsruhe Institute of Technology). Lead, iron, copper, calcium, potassium, among other elements, were detected and are correlated with red, blue, yellow and green pigments. In the fragments from Mülheim-Kärlich, red has high correlation with Pb (red lead pigment), Fe and Ca were detected in 2 different hues of yellow respectively, and Cu is correlated with the blue pigment. The green pigment investigated in the Wössingen's fragments has high correlation with Fe and K, indicating the use of green earth, and the red pigment is correlated with iron, indicating the use of the red ochre. Synchrotron-based scanning macro-X-ray fluorescence applied in fragments of wall paintings has shown to be a fast, non-destructive and effective technique in the identification and discrimination of the pigments, plaster, different layers and impurities in paintings through the 2D elemental distribution.