Fig. 8From: Analytical imaging studies of the migration of degraded orpiment, realgar, and emerald green pigments in historic paintings and related conservation issuesDetail of light microscopic image of The Descent of the Cattle sample (sample code: 286-A) under white light (a), the detail corresponds to the area measured for the µ-XRF and multi-energy maps. Elemental distribution maps of arsenic (b), copper (c), iron (d), chromium (e), and calcium (f) obtained with µ-XRF (data collection at SSRL BL 2–3; µ-XRF maps excited at 11,960 eV, map size (v × h): 342 × 128 µm). The layer composition and layer structure of the paint sample can be found in Table 1 and in Keune et al. [1]. The distribution of the As K-edge position where blue pixels indicate more reduced and orange/red pixels more oxidized As (g) and image segmentation based on PCA and k-means clustering (h). Arsenic -K-edge XANES spot analyses taken from emerald green reference sample (black), As–Cu rich particle (layer 6, magenta), iron-containing ground layer (layer 3, green), copper rich layer (layer 9–10, red) and varnish layer (layer 15–16, blue) (i). Average XANES of clusters 1–6 corresponding to the map shown in h (j). Note that the light microscopic image visualizes the surface and µ-XRF and multi-energy maps the paint volume of the sampleBack to article page