Pigment study by Raman microscopy of 23 paintings by the Portuguese artist Henrique Pousão (1859–1884)

Abstract

Twenty-three paintings by Henrique Pousão -a 19th century Portuguese painter -belonging to the collection of Museu Nacional Soares dos Reis, Porto, Portugal, were analysed by Raman microscopy. The fine focus of a 100× objective allowed the visualisation and individual identification of small grains. As a result, thirty-seven compounds, namely, anatase, barium white, basic lead sulfate, brochantite, cadmium red, cadmium yellow, calcium carbonate, carbon-based black, celadonite, chrome green, chrome orange, chrome yellow, cobalt blue, cochineal lake, copper sulfide, emerald green, iron(III) oxyhydroxide, iron(III) oxide, kaolinite, lead antimonate yellow, lead carbonate, lead white, lead sulfate, madder lake, malachite, Prussian blue, quartz, realgar/pararealgar, red lead, rutile, Scheele's green, strontium yellow, ultramarine blue, vermilion, viridian, zinc white and zinc yellow, were identified. Not all these compounds are pigments; some are extenders, others trace components and others probably products of reactions between pigments. Special attention was given to the Raman characterisation of celadonite, chrome orange, basic lead sulfate and lead antimonate yellow. Complementary techniques were used to confirm the identities of certain pigments and to characterise reference samples. Pousão, whose work has not previously been studied spectroscopically, was found to have used a remarkably wide range of pigments over his painting periods, without showing significant preference for any particular set of pigments.

Evidence for the Incorporation of Lead into Barite from Waste Rock Pile Materials

“…The ν1 band corresponds to the stretching of the S-O bond in the SO4 2-group (νSO4 2-) and is the most characteristic for determining the composition of the solidsolution between anglesite and barite. Thus, in our case, the ν1 band may also indicate the presence of Pb according to the ν1 band reported in previous work (33,41) and because of the shoulder at 973 cm -1 . Moreover, Lee et al (41) show that the Raman shift of the ν1 band is a function of the BaSO4 content in the (Ba, Pb)SO4 solid solution, ranging from 978.5 cm -1 for anglesite (44) to 986-990 cm -1 for barite (32-34, 41, 43).…”

“…From the Ba-rich end toward the Pb-rich end of the solid-solution series, the cell parameters vary continuously and systematically (40). In this study, the incorporation of Pb within barite is evidenced by the characteristic bands at 1047 cm -1 (PbO · PbSO4) (33) and by the shift of several bands reported in the Raman spectrum, for instance at 1071 and 1093 cm -1 as compared to those observed for pure barite at 1075 and 1110 cm -1 , which are attributed to the ν3 vibrational modes of PbSO4 (32). Furthermore, the peak of the symmetric stretching mode (ν1) measured at 986 cm -1 in our sample was already reported for pure barite in previous studies (e.g., ref 34) or with frequency values slightly higher at 987 (32, 43), 988 (33), or at 990 cm -1 (41).…”

“…The bands at 241, 296, 391, 548, 683, 1130, and 1298 cm -1 have been ascribed to goethite (23,30,31). Those at 456 (ν2), 617 (ν4), 631 (ν4), 986 (ν1), and 1130 (ν3) cm -1 have been ascribed to barite, with other weak bands at 1071 and 1093 cm -1 attributed to ν3 vibrational modes (32)(33)(34). The sharp ν1 band shows a shoulder at 973 cm -1 , and a very weak band has also been noted at 1048 cm -1 , close to bands obtained for PbO · PbSO4 phases at 976 and 1055 cm -1 (33).…”

“…Those at 456 (ν2), 617 (ν4), 631 (ν4), 986 (ν1), and 1130 (ν3) cm -1 have been ascribed to barite, with other weak bands at 1071 and 1093 cm -1 attributed to ν3 vibrational modes (32)(33)(34). The sharp ν1 band shows a shoulder at 973 cm -1 , and a very weak band has also been noted at 1048 cm -1 , close to bands obtained for PbO · PbSO4 phases at 976 and 1055 cm -1 (33). The Pb-rich phase is thus identified as a mixture of barite and goethite at the resolution of the Raman (here, 1 µm 3 ).…”

Barium, zinc and strontium yellows in late 19th–early 20th century oil paintings

“…The study of the materials and techniques of these painters was carried out in the framework of the interdisciplinary project 'Crossing Borders: History, materials and techniques of Portuguese painters from 1850 to 1918 (Romanticism, Naturalism and Modernism)' . Previously, Correia et al had identified barium and strontium chromate using μ-Raman in oil paintings by the Portuguese Naturalist Henrique Pousão (1859-1884) [22]. a The designation "lemon yellow" was also used for zinc and strontium chromates [5] but herein it will only refer to barium chromate b The solubility product constant of zinc yellow is not tabulated.…”