CdS1-xSex pigments: multidisciplinary study on the materials of the XIX-XX C. painters

The analysis of paintings can be very complex as they their variability in the material to create their piece, the artists mix and juxtapose different pigments (organic and inorganic), which are blended with a binder and covered with varnish. Then, the good or bad conservation of the paintings will affect the aging of the materials and their photochemical alteration.[1–4] When studying these artifacts, the lack of reference materials and the need to understand how the mixing of different materials affects the aging process requires (I) the analysis of samples taken from the painting, or (II) the preparation of mock-up samples, and the correlation of the data collected on these samples with those collected on the artistic artifact. However, when preparing mock-up samples, ensuring that the acquired material is effectively what is expected is essential. Indeed, modern industrial pigments may be prepared with different recipes and contain various fillers (or may be prepared with completely different pigments concerning those advertised), so their behavior and aging may differ from the historical materials. The study we propose starts with analyzing the famous painting ‘Quarto Stato’ by the Italian painter Giuseppe Pellizza da Volpedo at the beginning of the XX century. We focused on characterizing the yellow and red pigments used by the artist (and many contemporary artists, such as van Gogh, Munch, Matisse, and Picasso…). Indeed, CdS1-xSex[5, 6] is a family of pigments highly appreciated by artists of the late XIX and early XX centuries, thanks to their vibrant hues and excellent covering power. In this work, we will show the results of the characterization of a full set of CdS1-xSex pigments bought by Zecchi, with the application of different non-destructive spectroscopic techniques i.e. combined macro XRF-Reflectance Spectroscopy (RS), punctual-XRF, XRD, XAS on the S, Cd (K and L3), Se and Zn edges, Raman and FT-IR. We then compare the results of laboratory analysis (XRF, RS, Raman, and FT-IR) with those obtained from other commercial pigments. [1] G. Van der Snickt, J. Dik et al, Anal. Chem. 2009, 81, 2600. [2] F. A. Pisu, P. C. Ricci et al., Materials 2022, 15, 5533. [3] M. Ghirardello, V. Gonzalez et al, Microsc. Microanal. 2022, 30, 1. [4] L. Monico, F. Rosi et al, Eur. Phys. J. Plus 2022, 137, 311. [5] R. J. Traill and R. W. Boyle, Am. Mineral. 1955, 40, 555. [6] J. Wu, K. Li et al, Univ. Technol.-Mater Sci. Ed. 2015, 30, 124.