Pigments-Arsenic-based yellows and reds (original) (raw)
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Mineral Pigments in Archaeology: Their Analysis and the Range of Available Materials
Minerals
Naturally occurring minerals or their synthetic analogues have been important as pigments used in artistic and cosmetic contexts in global antiquity. The analysis and identification of mineral pigments, though routine to the petrologist or mineralogist, also requires specialist knowledge of the archaeological contexts and available technologies and trade. This paper attempts to present an analytical approach to the study of mineral pigments in archaeology and also introduces the range of mineral pigments encountered in works of art and painted objects on archaeological sites and in museums. It attempts to cover the range of mineral and synthetic inorganic pigments used in global cultures from to the early Medieval period.
Heritage, 2022
The painting The Descent from the Cross, painted in 1620 by Pedro Nunes (1586–1637), presents two large figures with orange-coloured fabrics with conservation problems. Through the analysis of two samples with several analytical techniques, especially scanning electron microscopy combined with X-ray spectroscopy and Raman microscopy, it was possible to conclude that the orange colour is due to a complex artificial pigment made of amorphous arsenic sulphide. It essentially consists of spherical particles obtained by sublimation and condensation, possibly from orpiment, which ended up being joined with irregularly shaped particles resulting from crushing of the residual fraction obtained by solidification and fusion. This is a rare documented case of the extensive use of artificial arsenic sulphides in European easel painting, especially outside Italy. The conservation problems can be explained by the great sensitivity of the arsenic sulphides to photodegradation and the formation of powdery compounds
2010
Sublimed (dry process) arsenic sulphide pigments have been of interest since historic and modern samples of yellow, orange or red powders and cakes containing arsenic oxide (As 2 O 3), arsenic sulphide glass (g-As x S x), members of the β-As 4 S 4-As 8 S 9 series, the χ-phase and pararealgar (As 4 S 4) were identified. The X-ray amorphous components occur as irregular masses or spherules, whereas the crystalline components consist of octahedral or tabular crystals or radially grown spherules of up to 30 μm in diameter. Artificial arsenic sulphides produced by sublimation have been found in the paint layers of a sixteenth/seventeenth-century South German polychrome recumbent sculpture in Altomünster and in Domenico Tintoretto's painting Entry of Philip II into Mantua (1579/80), which is part of the famous 'Gonzaga Cycle' (Alte Pinakothek, Munich). The identification required the use of light microscopy, X-ray diffraction and scanning electron microscopy as well as Raman analysis. Raman microspectroscopy proved to be a valuable tool, particularly for differentiation between realgar (As 4 S 4), pararealgar, and members of the β-As 4 S 4-As 8 S 9 series, which includes the χ-phase of almost identical chemical composition, as well as the distinction of X-ray amorphous arsenic sulphide glasses. If pure pararealgar is detected using Raman it is not possible to determine whether it was formed from degradation of natural realgar or from members of the β-As 4 S 4-As 8 S 9 series. Keeping in mind the close relationship between natural realgar, alacranite (As 8 S 9), β-As 4 S 4 and the χ-phase, it is highly likely that many of the arsenic sulphides found on works of art will turn out to be of artificial origin.
European Journal of Mineralogy, 2013
Among the four different ways (and their combinations) to colour a solid, the dispersion of a phase, already coloured and stable in the fired/molten matrix -a pigment -is the technique offering the largest palette. The pigment preparation involves sophisticated high-temperature routes and/or the use of selected, sometimes rare minerals. Consequently, ancient painters, potters, craftsmen and glassmakers selected natural rocks or minerals to obtain blue, green, red and black colours. For instance, the blue coloration requires the use of a rare element: cobalt. Pure cobalt ores spots were exceptional and the difficult purification of cobalt derivatives could be obtained during the 19 th century only. Thus, potters and glassmakers solved the problem by using recycling or specific minerals, for instance lapis lazuli, and developed convenient techniques with the use of mixed ores to obtain the blue, green, red or black colour. We discuss here enamelling/glazing technologies of ceramic and glass masterpieces with emphasis on the lapis lazuli use as blue or green pigment. We will reveal how the recent Raman microscopy studies deeply change our knowledge on the history of colouring techniques.
2010
In this paper, we generalize a mathematical definition of Gopakumar-Vafa (GV) invariants on Calabi-Yau 3-folds introduced by Maulik and the author, using an analogue of BPS sheaves introduced by Davison-Meinhardt on the coarse moduli spaces of one dimensional twisted semistable sheaves with arbitrary holomorphic Euler characteristics. We show that our generalized GV invariants are independent of twisted stability conditions, and conjecture that they are also independent of holomorphic Euler characteristics, so that they define the same GV invariants. As an application, we will show the flop transformation formula of GV invariants.
Heritage Science, 2019
This study explores the evolution of the manufacturing process of artificial arsenic sulfide pigments in Edo-period Japan through the analysis of three impressions of the same print dated from the 1830s and attributed to Katsushika Hokusai (1760-1849), and one from 1852 and attributed to Utagawa Kunisada (1786-1865). Colorants in the yellow and green areas of the four prints were investigated by means of non-invasive and microanalytical techniques such as optical microscopy, fiber optic reflectance spectroscopy and Raman spectroscopy. While the pigments in the green and yellow areas are similar throughout the set of prints-Prussian blue, indigo (for the Hokusai prints) and orpiment were identified-optical microscopy and Raman spectroscopy highlighted some variations in the orpiment used in the green areas of the prints. Two of the Hokusai prints present bright yellow particles of larger size and lamellar morphology, identified by Raman spectroscopy as natural orpiment. The third print presents an admixture of bright yellow natural orpiment particles with a smaller number of orange-yellow particles shown by Raman to be partially amorphous arsenic sulfide. Small bright yellow particles identified as fully amorphous arsenic sulfide pigments by Raman were found throughout the green areas of the Kunisada print. Although supported by Japanese historical sources, local production of artificial arsenic sulfide in the early nineteenth century was not previously documented. The simultaneous presence of both crystalline and amorphous domains in a single pigment particle in some of the Hokusai prints suggests that natural orpiment was used as primary source of arsenic for the production of a low grade artificial pigment. The pigment found in the Kunisada print, by contrast, was obtained from arsenic oxide (or arsenolite) and sulfur though a dry-process synthesis, as shown by the sulfur excess, signs of heat treatments and fully amorphous nature of the pigment. These findings set the earliest dates for both the ore sublimation process and the arsenolite dry process, and are of foremost importance to understand the evolution of the amorphous arsenic sulfide production in Edo-period Japan and its introduction in the palette of Japanese woodblock prints.
Archaeological and Anthropological Sciences, 2017
A non-invasive characterization study has been performed and here presented for the first time on the masonry altar of S. Maria ad Undas, a parish medieval church on the Idro (Brescia, Italy) lakeshore. The determination of painting materials and of alteration products represent the one of the first steps, together with art history studies, of a wider project aimed to the valorization of the site. Images collected under UV light in fluorescence and reflectance mode provided useful information about the presence of organic residual materials attributable to the application of lost gilding details, while the readability of some particulars was greatly improved with respect to what observable in visible light. Moreover, near infrared (NIR) images led to hypothesize the presence of green earths in green painted areas. Raman and reflectance spectroscopy allowed the identification of the pigments and of several alteration products, such as plattnerite, which derived by the degradation of the lead-based ones, hydromagnesite, gypsum, and niter, as well as of carbon-based depositions. Keywords Raman spectroscopy. Multispectral imaging. Medieval pigments. Wall paintings Highlights • Three never studied painted masonry altars exist in the Brescia province • A non-invasive characterization of the S. Maria ad Undas altar is presented • UV and NIR imaging allowed formulating hypothesis on pigment composition • Raman and FORS data on pigment and alteration phase compositions are stated Electronic supplementary material The online version of this article (