Identification by Raman microspectroscopy of pigments in seated statues found in the Torreparedones Roman archaeological site (Baena, Spain)

The combined use of SEM-EDX, Raman, ATR-FTIR and visible reflectance techniques for the characterisation of Roman wall painting pigments from Monte d'Oro area (Rome): an insight into red, yellow and pink shades

The aim of this work has been the identification of the painter's materials employed in the wall decoration of some destroyed buildings dating approximately between the first century B.C. and the first century A.D. This research originates from a previously started joined archaeological and analytical investigation concerning a varied group of findings that resulted from a rescue excavation performed by Soprintendenza Archeologica in the area of Monte d'Oro in Rome. The focus of this study progression has been directed to a numerous selection of monochrome red, pink and yellow-pigmented fragments. The analyses were performed by means of scanning electron microscopy energy dispersive X-ray spectroscopy (SEM-EDX) combined with Raman and Fourier transform infrared (FTIR) spectroscopies; visible reflectance measurements have also been carried out and the relevance of this technique in such a kind of archaeological studies has been highlighted. Most attention has been given to the assessment of the performances of non-destructive techniques achieved by portable Raman, and visible reflectance instrumentation to test their diagnostic capabilities. In addition to the expected and well-known pigments such as cinnabar, red ochre, hematite for the reds and yellow ochre for the yellows, the study highlighted a diffuse use of mixed colours and in some cases the possible presence of overlapped painted layers and confirmed the presence of gildings. Among the mixtures of pigments, the most singular outcome concerns the pink fragments revealing the possible application of bone white, which seems to be rather uncommon as a pigment in Roman wall decorations.

Spectroscopic investigation and comprehensive analysis of the polychrome clay sculpture of Hua Yan Temple of the Liao Dynasty

This article shows the investigation results of the polychrome clay sculptures in Hua Yan Temple of the Liao Dynasty in Datong, China. The mineral pigments, adhesive and painting techniques used in these cultural relics were systematically analyzed in this project. Optical microscope (OM), Scanning electron microscope coupled with an energy-dispersive X-ray spectroscopy (SEM-EDS), micro-Raman, Fourier transform infrared spectrometer (FT-IR) and Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) analyses were selected as scientific micro-destructive analytical methods. The results show that the pigments in the polychrome clay sculptures include cinnabar, lead red, malachite, atacamite, azurite, orpiment and gold. Meanwhile, the presence of nitrogen-containing substances and glue-marker characteristic pyrolysis products clearly indicates that the adhesive used in most of the polychrome clay sculptures was glue-protein. Additionally, the combination of heat-bodied tung oil and glue-protein was also found in the golden areas.

A multi-analytical study of a wall painting in the Satyr domus in Córdoba, Spain

In this work, we conducted a careful study of the mortar and paint in the Roman wall painting housed by the triclinium of the so-called Domus in the Road Safety Education Park of Córdoba, Spain. A combination of X-ray diffraction, Raman and X-ray fluorescence spectroscopies allowed the different substances used to obtain the pigments present in the painting to be identified. The painting was found to contain five different colours (red, yellow, blue, green and white) in various hues. The red pigment was obtained from hematite and the yellow pigment from goethite. The blue pigment, which was the least abundant, was prepared from Egyptian blue, and the green pigment from green earths. Finally, the white pigment came from lime. The binders used were identified by infrared spectroscopy and gas chromatography with mass spectrometry detection. The painting fragments studied contained vestiges of bee wax or its decomposition products, which suggests that the paint was applied encaustically.

Highly efficient WO3-FeOx catalysts synthesized using a novel solvent-free method for NH3-SCR

WO₃-FeO_x catalysts with various WO₃ contents were synthesized through a facile solvent-free method, satisfying the selective catalytic reduction of NO (NH₃-SCR). Strikingly, the optimum 30 %WO₃-FeO_x catalyst with the largest surface area exhibited the most outstanding catalytic activity, achieving the nearly 100 % NO_x removal efficiency in a wide temperature window between 225-500 °C, which was better than that of Fe-W series catalysts reported in other studies. In addition, Raman and XPS results proved that the introduction of WO₃ altered the electronic environment of Fe₂O₃, inducing the formation of Fe₃O₄ (Fe²⁺) and surface adsorbed oxygen. In situ DRIFTS demonstrated that the interaction between WO₃ and Fe₂O₃ not only promoted the adsorption capacity of NH₃ on the catalyst, but also contributed to the formation of adsorbed NO_x species. NO_x reduction reaction on WO₃-FeO_x catalyst proceeded via the Eley-Rideal and Langmuir-Hinshelwood mechanism synchronously. All of these factors, jointly, accounted for the superior catalytic activity and N₂ selectivity of WO₃-FeO_x catalysts.

Identification of pigments in the Annunciation sculptural group (Cordoba, Spain) by micro-Raman spectroscopy

A highly flexible method based on micro-Raman spectroscopy was used to examine pigment traces on an Annunciation sculpture group dating from the late Middle Ages. The group comprises a statue of the Archangel Gabriel and another of the Virgin Mary. Both are currently housed in the Archaeological Museum of Cordoba, southern Spain. Information about the pigment palette used by the artists of the time to decorate religious limestone sculptures was for the first time obtained. The pigments found included vermilion (HgS), hematite (α-Fe₂O₃), azurite [Cu₃(CO₃)₂(OH)₂], cerussite (PbCO₃) and anatase (TiO₂). None was directly applied to the sculptures; rather, the limestone was coated with a primer containing calcium carbonate (possibly chalk or half-chalk). The polychromy on both sculptures, which was originally applied in the XV century and seriously damaged in the XVIII, had been treated with an ochre-coloured priming layer of gypsum to make it more uniform and optically similar to the underlying stone.

Spectroscopic analysis of corrosion products in a bronze cauldron from the Late Iberian Iron Age

Selected bronze fragments unearthed at Cerro de la Cruz (Almedinilla, southern Spain) were analyzed to determine the chemical composition of the corrosion products formed on their surface. The fragments came from a large bronze cauldron used in an Iberian village that was devastated in the mid II century BCE - possibly around 141 BCE. The fragments were analyzed by using various instrumental techniques including electron scanning microscopy coupled to energy dispersive X-ray spectroscopy (SEM-EDS), X-ray fluorescence (XRF) spectroscopy, and also by X-ray diffraction (XRD) and micro-Raman spectroscopy. Based on the results, being buried for a long time caused the main elements in the alloy to mineralize and form stratified layers consisting of various mineral phases including cuprite (Cu₂O), malachite [Cu₂CO₃(OH)₂] and cassiterite (Sn₂O). The fragments also contained chloride and trihydroxychloride compounds such as nantokite (CuCl) and atacamite [Cu₂Cl(OH)₃], respectively, which make conservation of archaeological objects troublesome. These results testify to a strong interaction of the alloy elements with soil components. Also, the results obtained suggest a Type I of corrosion structure. Using the SEM-EDS, XRD and XRF and micro-Raman spectroscopies allowed corrosion products in the fragments to be successfully characterized in microchemical and structural.