From: Faded shine…. The degradation of brass powder in two nineteenth century paintings
Sample | ATR–FTIR–FPA | LM | XRF | SEM–EDX | Overall interpretation |
---|---|---|---|---|---|
Metallic flakes | No signal | Metallic leaf fragments 1–2 μm thick and up to 40 μm long, embedded in the paint | Cu Zn | Cu 90 Zn 10 | Brass metal leaf |
Green agglomerates | 2921, 2851, 1741, 1710, 1585, 1540, 1459, 1441, 1413, 1316, 1166 cm−1 copper and zinc carboxylates, free fatty acids and carboxylate esters | Green, non-fluorescent material involving the metal leaf fragments. Present throughout the paint layer. Dimensions relate to those of the metal fragment present in the core of the agglomerate | Cu Zn | Cu, Zn, Cl | Reaction phase between oil phase and the copper and zinc in the metallic pigment |
Paint build-up | 1-Ground n/a 2-Red paint layer 2921, 2851, 1737 cm−1; 1086 cm−1 quartz; 3750, 3695, 3650, 3620, 1086, 1010, 913 cm−1 kaolinite, 1400 cm−1 carbonate calcium 3-Beige paint layer 2956, 2918, 2848, 1737, 1710, 1236, 1162 cm−1 Lipids (drying oil and wax) 1795, 1410 carbonate; 1510 lead carboxylate, 1086 quartz cm−1 1034, 913 cm−1 clay minerals 4-Grey overpaint 1457, 1403, 1027 cm−1 calcium phosphate (bone black) 1400, 1044 cm−1 lead white, 1511 lead carboxylate 2950, 2920, 2850, 1737, 1240, 1163 cm−1 oil | 1-White ground layer 2-Red paint layer 3-Beige layer: (red, blue, yellow and white pigment particles) 4-Grey overpaint: White and black pigment particles | n/a | 1-Ground layer: Ca, S, O and Ca, C, O (in individual particles) 2-Red paint layer: Fe, Ca (localized in particles), Al, Si, Pb (finely dispersed), Mn, S, Cl 3-Beige paint layer: Pb (finely dispersed) Zn, Al, Si, Ca (localized in particles), Cl 4-Grey overpaint: Pb, Ca, P, Cl | 1-The ground layer is composed of a mixture of calcium sulphate and calcium carbonate 2-The red paint is oil containing pigmented with red earth pigment 3-The beige paint layer is pigmented with yellow and orange earth pigments, bound in oil 4-The grey overpaint contains lead white and bone black pigments in oil |