Fig. 6From: Concerns over colour durability in the nineteenth-century industrial revolution: insights from John Ruskin’s teaching collectionTop left: Study of Clouds, Norwood (WA.RS.ED.289bis.b). Top right: macro-XRF maps of chromium (green) and barium (red) overlapping a stitched image of the watercolour. Bottom: XRD diffractogram of the pale yellow wash, the asterisks indicate peaks from the paper supportBack to article page