title: The efficiency of micro-Raman spectroscopy in the analysis of complicated mixtures in modern paints: Munch's and Kupka's paintings under study.
abstract: Twenty one mock-up samples containing inorganic pigments primarily used at the turn of the 19th and 20th century were selected for comparative study and measured by micro-Raman and portable Raman spectrometers. They included pure grounds (chalk-based, earth-based and lithopone-based), grounds covered by resin-based varnish, and different paint layers containing mixtures of white, yellow, orange, red, green, blue and black pigments, usually in combination with white pigments (titanium, zinc and barium whites or chalk). In addition, ten micro-samples obtained from seven paintings of two world-famous modern painters Edvard Munch and František Kupka have been investigated. Infrared reflection spectroscopy (FTIR), portable X-ray fluorescence (XRF) and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) were used as supplementary methods. The measurements showed that blue pigments (ultramarine, Prussian blue and azurite), vermilion and ivory black in mixture with whites provided characteristic Raman spectra, while Co-, Cd- and Cr- pigments' bands were suppressed by fluorescence. The best success rate of micro-Raman spectroscopy has been achieved using the 780 nm excitation, however, the sensitivity of this excitation laser in a portable Raman instrument significantly decreased. The analyses of micro-samples of paintings by E. Munch and F. Kupka showed that micro-Raman spectroscopy identified pigments which would remain unidentified if analyzed only by SEM-EDS (zinc yellow, Prussian blue). On the other hand, chromium oxide green and ultramarine were not detected together in a sample due to overlap of their main bands. In those cases, it is always necessary to complement Raman analysis with other analytical methods.
authors.affiliation: Academy of Fine Arts in Prague, ALMA laboratory, U Akademie 4, 170 22 Prague 7, Czech Republic; Department of Chemistry, Faculty of Science, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic. Electronic address: weronika.kosarova@gmail.com.
authors.forename: Veronika
authors.initials: V
authors.lastname: Košařová
authors.affiliation: Academy of Fine Arts in Prague, ALMA laboratory, U Akademie 4, 170 22 Prague 7, Czech Republic; Institute of Inorganic Chemistry of the AS CR, v.v.i., ALMA laboratory, 250 68 Husinec-Řež, Czech Republic.
authors.forename: David
authors.initials: D
authors.lastname: Hradil
authors.affiliation: Academy of Fine Arts in Prague, ALMA laboratory, U Akademie 4, 170 22 Prague 7, Czech Republic.
authors.forename: Janka
authors.initials: J
authors.lastname: Hradilová
authors.affiliation: Academy of Fine Arts in Prague, ALMA laboratory, U Akademie 4, 170 22 Prague 7, Czech Republic; Institute of Inorganic Chemistry of the AS CR, v.v.i., ALMA laboratory, 250 68 Husinec-Řež, Czech Republic.
authors.forename: Zdeňka
authors.initials: Z
authors.lastname: Čermáková
authors.affiliation: Department of Inorganic Chemistry, Faculty of Science, Charles University in Prague, Hlavova 8, 128 40 Prague 2, Czech Republic.
authors.forename: Ivan
authors.initials: I
authors.lastname: Němec
authors.affiliation: Institute of Science and Technology in the Art, Academy of Fine Arts, Schillerplatz 3, A-1010, Vienna, Austria.
authors.forename: Manfred
authors.initials: M
authors.lastname: Schreiner
keywords: Micro-Raman spectroscopy; Modern paints; Portable Raman spectrometry