Non-destructive XRF analysis of pigments in a 15th century panel painting

Abstract

The Retable of the Passion of Christ (towards 1415) forms part of the permanent exposition of the Museum of Fine Arts of Seville. It was painted by an anonymous author, who shows stylistic influences of Juan Sánchez de Castro, the most significant artistic figure in the Seville’s painting of the 15th century. The retable is composed by a main scene, “The Christ carrying the cross”, and two smaller scenes at each lateral side. On the left side above there is “The Agony in the Garden”, below “The Flagellation”, at the right side the “Crucifixion” and below it “The Pietà”. The panel was analyzed by the non-destructive XRF technique directly in situ in the exposition room, using portable equipment with X-ray tube of 30 kV, anode of W and one SDD detector with energy resolution of 140 eV. The goal of this research was to know which pigments were applied in this artwork. The analysis revealed that the white pigment is lead white, maybe mixed with small amount of calcium white. The red pigment is cinnabar (characteristic Hg peaks), applied also in the carnations together with lead white. Some red ochre and some organic red pigment were added, as well. The blue pigment is azurite, identified by high peaks of Cu. High copper peaks were found also in the green pigment, which is probably verdigris (according to its intensive colour). The brown colour was obtained by natural or burned yellow ochre (Ca, Fe) and umbra (Mn, Fe). The black pigment is of organic origin, not possible to identify by XRF. The aureoles are gilded (Au), under gold there is red bole (Fe). Spectra of some analysed points show peaks of Zn and Ba, revealing the use of modern material lithopone and therefore some later restoration. This is confirmed also by low Cd peaks in some red areas, showing the use of modern cadmium red.