X-RAY NANOPROBE

90 ESRF

where cadmium sulfide (CdS)-based pigments (also called cadmium yellows) have been used. In the cloudy sky and in the central character s neck area, some yellow brushstrokes have turned to an off-white colour; in the lake area, a thickly applied opaque yellow paint is flaking. Several factors have contributed to the degradation throughout time: the variety of yellow pigments used, the storage conditions and the theft of the ca. 1910 version in 2004, when the artwork disappeared for two years. Following its recovery, this version of The Scream is now kept in a private storage room at the Munch Museum under controlled lighting, temperature (~18°C) and relative humidity (~50%) conditions.

Earlier studies of paint microsamples of The Scream (ca. 1910) showed that cadmium carbonate (CdCO3) is a main component of the paler yellow paints of the sky and the central character s neck. In the lake area, the same compound had been found mixed with varying amounts of sulfur-, chlorine- and sodium- containing species, which are usually associated with residues of the starting reagents used for manufacturing the cadmium yellow [1]. This raised questions around a possible correlation between the extent of degradation of cadmium yellow paint and its chemical composition, the compound(s) into which the cadmium yellow had degraded and the causes of the yellow paint s degradation.

To answer these questions, selected CdS-based areas of The Scream (ca. 1910) were analysed by means of in-situ non-invasive elemental and molecular spectroscopy methods. In addition, a series of paint microflakes (Figures 74b,c), obtained by scraping off a spot of the flaked

Fig. 74: a) Photograph of The Scream (ca. 1910) with indication of the sampling spot and degraded cadmium yellow paint areas.

b-c) Photomicrographs of the analysed paint microflakes. Rectangles show the regions

analysed by X-ray methods (see Figure 75).

Fig. 75: a) μ-XRD maps of Cd(OH)Cl/CdSO4/CdCO3 and μ-XRF maps of b) S-II/SVI/Cd and c,f) Cl/K recorded from paint microflakes of The Scream (ca. 1910). Selection of d) S K-edge and e,g) Cl K-edge µ-XANES spectra obtained from the spots indicated in b,c,f).