Several glass mosaic tesserae were recovered during the archeological excavation of the thermal baths at the 'Villa dei Quintili' in Rome and dated to the second century AD. This work reports the results of an archeometrical investigation performed, through a multi-technique approach, on 19 colored opaque tesserae. The aims of the study were (1) the characterization of coloring and opacifying agents used for the production of the glass tesserae and (2) the definition of the technological processes involved. Colorimetric measurements allowed us to classify the tesserae in color groups, while the glassy matrix and the dispersed crystallites were characterized in detail through micro-Raman spectroscopy, field emission scanning electron microscopy with energy dispersive X-ray spectroscopy, laser ablation-inductively coupled plasma-mass spectrometry, and X-ray powder diffraction analyses. Most of the glass shows the typical soda-lime-silicate composition (except for the orange and red tesserae). Raman results and elemental analysis prove the use of Sn-Pb antimonates to create yellow glass and of Ca-antimonates for the white tesserae. A mixture of Sn-Pb antimonates and copper ions was used to obtain the emerald green color, while Ca-antimonates were employed in both copper-colored and cobalt-colored blue glass to obtain different shades (blue-green, dark, and light blue). X-ray powder diffraction analyses reveal the presence of metallic copper (Cu 0 ) and Cu 2 O particles (cuprite) in red and orange tesserae, respectively. These results confirm the high technological level reached by the glassmakers of the Imperial Age.
Decades of technological and methodological advances in Raman spectroscopy have brought this technique from laboratory innovation to a well-established analytical tool with increasing applicability to the study of cultural heritage objects. Enduring research in the field of miniaturization has given rise to new generations of mobile, portable, and handheld spectrometers that have deeply transformed the way in which scientists approach materials analysis. Although sometimes limited in terms of performance and flexibility compared with their benchtop counterparts, miniaturized instruments are typically compact and light, user-friendly, and equipped with fiber optics and batteries, thus
A multi-analytical investigation of Japanese woodblock prints ranging in date from 1864 to 1895 and covering essentially the time span between the very end of the Edo period and the middle of the Meiji period showed a widespread use of arsenic sulfides for yellow and green colored areas (the latter obtained by mixing Prussian blue to the yellow arsenic sulfides). Analysis by optical microscopy, X-ray fluorescence spectroscopy, Raman microscopy, and Scanning Electron Microscopy confirmed that the yellow pigment is usually a compound belonging to the solid solution series (As 8 S 8 )-(As 8 S 9 ). The poor crystallinity of the pigment as shown by Raman microscopy, the non-stoichiometric As/S ratio, as well as the presence of excess uncombined sulfur point to a synthetic origin for the pigment. Period literary sources suggest that synthetic arsenic sulfide pigments manufacture might have started in the Iwashiro province in 1846. This is to our knowledge the first conclusive evidence for the use of synthetic arsenic sulfides in woodblock prints in Japan.
Three Japanese woodblock prints from the Edo period (1603–1868) underwent a scientific investigation with the aim of understanding the changes in the colorants used in Japanese printing techniques. A multi-analytical approach was adopted, combining non-invasive techniques, such as fiber optic reflectance spectroscopy (FORS), Raman spectroscopy, multispectral imaging (MSI), and macro X-ray fluorescence (MA-XRF) with minimally invasive surface-enhanced Raman spectroscopy (SERS). The results enabled many of the pigments to be identified and their distribution to be studied, apart from two shades of purple of organic composition. Consequently, the potential of high-pressure liquid chromatography tandem mass spectrometry (HPLC–MS/MS) was explored for the first time with application to Japanese woodblock prints. The intrinsic sensitivity of the instrument and an effective extraction protocol allowed us to identify a mixture of dayflower (Commelina communis) blue and safflower (Carthamus tinctorius) red in purple samples constituted of 2–3 single fibers. In addition to the innovative integration of MA-XRF and HPLC–MS/MS to investigate these delicate artworks, the study concluded on the use of traditional sources of colors alongside newly introduced pigments in late Edo-period Japan. This information is extremely important for understanding the printing practices, as well as for making decisions about display, conservation, and preservation of such artworks.
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