title: On the Use of the Unusual Green Pigment Brochantite (Cu₄(SO₄)(OH)₆) in the 16th-Century Portuguese-Flemish Paintings Attributed to The Master Frei Carlos Workshop.
abstract: This paper reports an unusual green pigment, brochantite (Cu4(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-Flemish Master as a natural pigment rather than its accidental use as an alteration product. This seems to be a distinguishable feature to other painters (Flemish and Portuguese) working in Portugal at the beginning of the 16th century. The multi-analytical study of these easel paintings was first performed by physical imaging techniques and material characterization was carried out by optical microscopy, micro-Fourier-transform infrared-spectroscopy, micro-Raman spectroscopy, scanning electron microscopy coupled with energy dispersive X-ray spectrometry, and micro-X-ray diffraction analysis (XRD).
authors.affiliation: 1Évora University,HERCULES Laboratory,School of Sciences and Technology,Largo Marquês de Marialva 8,7000-809 Évora,Portugal.
authors.forename: Sara
authors.initials: S
authors.lastname: Valadas
authors.affiliation: 1Évora University,HERCULES Laboratory,School of Sciences and Technology,Largo Marquês de Marialva 8,7000-809 Évora,Portugal.
authors.forename: Rita V
authors.initials: RV
authors.lastname: Freire
authors.affiliation: 1Évora University,HERCULES Laboratory,School of Sciences and Technology,Largo Marquês de Marialva 8,7000-809 Évora,Portugal.
authors.forename: Ana
authors.initials: A
authors.lastname: Cardoso
authors.affiliation: 1Évora University,HERCULES Laboratory,School of Sciences and Technology,Largo Marquês de Marialva 8,7000-809 Évora,Portugal.
authors.forename: José
authors.initials: J
authors.lastname: Mirão
authors.affiliation: 1Évora University,HERCULES Laboratory,School of Sciences and Technology,Largo Marquês de Marialva 8,7000-809 Évora,Portugal.
authors.forename: Cristina B
authors.initials: CB
authors.lastname: Dias
authors.affiliation: 3Department of Archaeology,Ghent University,Sint-Pietersnieuwstraat 35,B-9000 Ghent,Belgium.
authors.forename: Peter
authors.initials: P
authors.lastname: Vandenabeele
authors.affiliation: 1Évora University,HERCULES Laboratory,School of Sciences and Technology,Largo Marquês de Marialva 8,7000-809 Évora,Portugal.
authors.forename: António
authors.initials: A
authors.lastname: Candeias
keywords: brochantite