On the use of the unusual green pigment Brochantite (Cu-4(SO4)(OH)(6)) in the 16th-century Portuguese-Flemish paintings attributed to the master Frei Carlos workshop

This paper reports an unusual green pigment, brochantite (Cu-4(SO4)(OH)(6)), on 16th-century Portuguese-Flemish paintings, attributed to the Master Frei Carlos workshop. This green mineral is usually identified as an impurity or alteration product in the green pigments verdigris (Cu(CH3COO)(2) nCu(OH)(2)) or malachite (CuCO3 Cu(OH)(2)). However, after thorough investigation with a broad range of analytical techniques, it became clear that, in this case, brochantite was applied as a pigment. The abundance, pigment granulometry, and pigment morphology suggest intentional use by this Portuguese-F... Mehr ...