https://doi.org/10.1140/epjp/s13360-023-03847-z
Regular Article
Non-invasive evidence of mercury soaps in painted miniatures on ivory
1
Institute of Inorganic Chemistry of the Czech Academy of Sciences, ALMA Laboratory, 250 68, Husinec-Řež, Czech Republic
2
Academy of Fine Arts in Prague, ALMA Laboratory, U Akademie 4, 170 22, Prague 7, Czech Republic
Received:
6
October
2022
Accepted:
25
February
2023
Published online:
8
March
2023
This work focuses on a non-invasive study of two selected painted miniature portraits on ivory to describe the degradation processes resulting from the interaction between mercury-based and lead-based pigments with oils. In the studied miniatures, containing both lead white and cinnabar, the formation of metal soaps has been clearly detected. However, until now they have been identified exclusively as lead soaps. In this study, the formation of mercury soaps has been evidenced in painted artworks for the first time, together with the well-known lead soaps. The fully non-invasive analytical approach involved the use of large-area X-ray fluorescence scanning, X-ray powder diffraction and Fourier transform infrared spectroscopy accompanied by Raman spectroscopy. It enabled complex description of the miniatures, leading to both the identification and the deduction of approximate composition of mercury soaps. In addition, approximate calculations of the amount of pigments consumed by saponification unveiled the complex processes taking place in the oil-based paint containing both cinnabar and lead white, which were further studied within long-term model experiments monitored by both Fourier transform infrared spectroscopy and X-ray powder diffraction.
© The Author(s) 2023
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