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Fig. 8 | Heritage Science

Fig. 8

From: Analytical imaging studies of the migration of degraded orpiment, realgar, and emerald green pigments in historic paintings and related conservation issues

Fig. 8

Detail 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 16 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 sample

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