Fig. 3From: Concerns over colour durability in the nineteenth-century industrial revolution: insights from John Ruskin’s teaching collectionTop left: Study of Dawn: purple Clouds (WA.RS.ED.005). Top right: macro-XRF maps of cobalt (green), phosphorus (blue), and potassium (red). Middle: XRF spectrum of the bright blue area. Bottom: XRD diffractogram of the bright blue area, the asterisks indicate peaks from the paper supportBack to article page