Protrusions in a painting by Max Beckmann examined with confocal μ-XRF

Max Beckmann's "Pierrette und Clown'' (Pierrette and Clown), 1925, is undoubtedly one of the major works in the collection of the Kunsthalle Mannheim, Germany. In this painting, damages can be seen, described as protrusions. These are blisters and crater-like holes, filled with metallic soap aggregates. Painting samples and cross-sections of the ground layer have been examined by environmental scanning electron microscopy (ESEM) and by confocal synchrotron radiation micro-X-ray fluorescence (CSR mu XRF) in order to get compositional and spatial distribution information about the components and their behaviour. The analyzed samples of the unpainted ground layer consist of lithopone (ZnS center dot BaSO(4)), as several bulges resembling small blisters, presumably protrusions in the nascent state. Direct CSR mu XRF measurements on closed blisters showed that these blisters have a high concentration of zinc in the centre with surrounding layers of barium and strontium. Relatively small amounts of lead have been recorded. In order to determine the composition of the organic compounds (e.g. fatty acids) and of the inorganic pigments (lead white, zinc white, lithopone), Raman spectroscopy has been successfully applied to flakes of an opened protrusion. The obtained Raman spectra could be assigned to derivatives of fatty acids and lithopones. These results allow conclusions to be made about the chemical behaviour by measuring the identical sample spot of the protrusion with CSR mu XRF as well as Raman spectroscopy.