Search Results (12)

The present study, which is part of a wider inter-disciplinary research project on Medieval Rome funded by the Swiss National Science Foundation, focuses on the archaeometric characterisation of glass tesserae from the apse mosaic of the church of S. Agnese fuori le mura, dated to the 7th century AD and never analysed until now. The main aims of the study are the identification of chemical compositions of glassy matrices and colouring/opacifying techniques by means of the combination of micro-textural, chemical, and mineralogical data. In S. Agnese tesserae, the results show the presence of glassy matrices and opacifiers/pigments, typical of both Roman and Late Antique/Early Medieval periods. The technological features identified (in particular, glassy matrices and opacifiers/pigments) allow us to discriminate not only new-production tesserae, i.e., those probably produced in the 7th century for the realisation of the S. Agnese mosaic, but also those obtained from recycling or re-using previous glass. This testifies to a quite complex “puzzle”, unusual in other glass mosaics from the same city and coeval with S. Agnese, supporting further the potentiality of archaeometric studies on glass to uncover the technical and socio-cultural knowledge that underpins its manufacturing, use, re-use, and recycling in the Early Medieval Rome. Full article

Raw materials significantly determine the final composition and properties of a fired ceramic. Raman analysis which characterizes micro- and nanostructures of (coloured) glazes, opacified or not, was applied to shards mostly collected before the 1960s, currently at the Louvre Museum, originated in Anatolia, the Caucasus, Iran and Central Asia, which are, for most of them, characterized by the use of black lines to separate coloured areas, and dated to the period between the 12th and 19th centuries. Measurements were carried out in the laboratory with a blue laser excitation and/or on the conservation site with a mobile device (green laser). Three types of glazes were identified by their nanostructure of the silicate network: (i) a lead-rich glaze analogous to that of Byzantine, Zirid to Hafsid and al-Andalus productions, (ii) a lead-alkali glaze typical of the Ottoman productions of Iznik-Kütahya, and (iii) a mixed (poor lead/lead-free)-alkali glaze typical of Safavid productions. The colour determines the precise composition of the glaze. The identification is not only based on the signature of the stretching mode of the SiO₄ tetrahedron (position of the wavenumber of the component(s)) but also on the position and shape of the continuous luminescence of the Raman background, characteristic of the raw materials used. Lead-tin yellow, Fe-rich, Mn-rich and Cr-rich black pigments and opacifiers made of cassiterite and wollastonite were also identified. The results (type of glaze and deduced processing temperature) were discussed in the light of the ternary phase diagrams visualizing elemental composition determined in previous works and the microstructure examination on the polished section (defining single or multistep firing cycles). Continuity was highlighted on the one hand between the tiles of Bursa, Edirne and Istanbul (Ottoman Iznik-like production) and on the other hand between those of Samarkand area (Timurid) and Iran. The procedure was then applied in the study of three objects (two dishes and a bowl) which are very representative of the productions of the Turkish-Persian cultural areas: a polychrome mina’i cup with decoration representing a rider, an Ottoman Iznik fritware with polychrome floral decoration, and a blue-and-white Safavid ceramic with a decoration representing a shrub. Full article

Modern light-cured, resin-based composites are offered in a wide range of shades and translucencies. This large variation, created by varying the amount and type of pigmentation and opacifiers, is essential to enable an esthetic restoration in each patient situation, but may affect light transmission in the deeper layers during curing. We quantified optical parameters and their real-time variation during curing for a 13-shade composite palette of identical chemical composition and microstructure. Incident irradiance and real-time light transmission through 2 mm thick samples were recorded to calculate absorbance, transmittance, and the kinetic of transmitted irradiance. Data were supplemented by the characterization of cellular toxicity to human gingival fibroblasts up to 3 months. The study highlights a strong dependence of light transmission and its kinetic as a function of shade, with the largest changes occurring within the first second of exposure; the faster changes, the darker and more opaque the material. Transmission differences within progressively darker shades of a pigmentation type (hue) followed a hue-specific, non-linear relationship. Shades with similar transmittance but belonging to different hues were identified, while the corresponding kinetic was identical only up to a transmittance threshold. A slight drop in absorbance was registered with increasing wavelength. None of the shades were cytotoxic. Full article

Roman glass is well studied and known to have been produced from a mineral soda source and calcareous sand with variation between elements relating to naturally occurring minerals in the sands. While the common characteristics of colourants and opacifiers used in opaque and translucent glasses are well understood, the diverse elemental composition of colouring agents associated with the highly specialised, and largely unexplored, technique of enamel-painted glass has never been firmly established. There remains a significant gap in knowledge of pigments used for this technological innovation which is here addressed through the deployment of non-invasive portable X-ray Flourescence (pXRF) analysis and microphotography on a unique Roman enamel-painted gladiator glass from Vindolanda fort. This vanguard research has successfully established, for the first time, a palette of pigments associated with this specialist technique. It is now possible to unravel previously unknown information on complex manufacturing processes and significantly expand the repertoire of the pigments bound up in enamelling recipes used to depict the striking iconographic scenes on the Vindolanda vessel and, potentially, other Roman enamelled glassware. The detection of Cinnabar, Egyptian blue, Orpiment and other pigments are ground-breaking discoveries that will have a transformative impact on early glassmaking studies and push the boundaries of scholarship into new directions of analytical approaches in heritage materials science to complement recent success in this field with Raman spectroscopy and other techniques. The methodology is unprecedented and has been validated through the high quality of the resulting data which permits the extrapolation of elemental compositions of enamelling materials from those associated with the base vessel. This unique approach provides remarkable insights that will revolutionise our understanding of enamelling technologies using the Vindolanda vessel as the investigative platform for forgotten practice. Full article

On-site pXRF analysis in various French collections (Musée du Louvre, Musée national des Arts asiatiques-Guimet, Paris) of porcelains decorated with painted enamels from the Qing Dynasty, in particular porcelains bearing an imperial mark, identifies the types of enamels/glazes, the ions and coloring phases or the opacifier. The study of the elements associated with cobalt (nickel, manganese, arsenic, etc.) and of the impurities of the silicate matrix (yttrium, rubidium and strontium) differentiates the use of ‘Chinese/Asian’ raw materials from ones imported from Europe by the initiative of the European missionaries (chiefly Jesuits) present at the Court (Beijing). Particular attention is paid to the analysis of the blue color of the marks and to the elements associated with the use of gold or copper nanoparticles as well as to the compositions of the pyrochlore phases (tin yellow, Naples yellow). The comparison is extended to pXRF and Raman microspectroscopy measurements previously made on other Qing imperial porcelains as well as on Cantonese productions (on porcelain or metal) from different Swiss and French museums and blue-and-white wares of the Ming and Yuan Dynasties (archaeological and private collections). Full article

In order to improve thermomechanical, antibacterial and temperature-controlled color-response performance of polydimethylsiloxane (PDMS) in maxillofacial prostheses, the incorporation of titania (TiO₂) nanoparticles and thermochromic pigments (TCP) into PDMS was examined. The thermal transitions of TiO₂/PDMS nanocomposites, investigated by differential scanning calorimetry (DSC), remain almost unaffected, while an increase of the crystallinity of PDMS was recorded in specimens with higher titania concentrations. The incorporation of titania improves the thermal stability, as it was revealed by thermogravimetric analysis (TGA), as well as the tensile properties of the reinforced elastomer. Nanocomposites with 10 wt% titania presented antibacterial activity against Escherichia Coli, leading to 72% reduction of the bacterial colony after 3 h of exposure. Specimens colored with red TCP (0.2 and 0.6 wt%) showed significant color change at a lower temperature (−20 °C) in comparison with that at an ambient temperature, especially at lower TCP concentration (0.2 wt%). Accelerating aging experiments, consisting of repeated cycles of combined exposure to UV-radiation and damp heating, of PDMS colored with TCP showed poor color stability of the specimens, from the first hours of exposure. The addition of titania to polysiloxane specimens works as an opacifier providing a positive effect on the color stability of the examined thermochromic pigment. Full article

In this work, micro-Raman spectroscopy and micro-energy-dispersive X-ray fluorescence spectroscopy (µ-EDXRF) were applied on microsamples taken from the Plaiko Zubixe footbridge (1927) located in Ondarroa (Basque Country, Spain) in order to investigate the original paint coating and make an evaluation of the conservation state before its restoration. Elemental and molecular images were acquired for the study of the compounds distribution. Some modern pigments such as phthalocyanine blue and green pigments, minium, calcium carbonate, Prussian blue, and hematite were identified. Barium sulfate and titanium dioxide were recognized as opacifier agents. Thanks to the study of the stratigraphies, it has been possible to determine the original paint layer, which includes lead white, ultramarine blue, carbon black, and barium sulfate. In addition, colorimetric analyses made it possible to know the CIELab values of the original layer in order to reproduce the original colour during the planned restoration work. The massive presence of chlorine detected by µ-EDXRF and the corrosion products of the rust layer, in particular akaganeite and hematite, highlighted the atmospheric impact in the conservation of the bridge because they were due to the effect of both marine aerosol and to the presence of acidic components in the environment coming from anthropogenic activity. This work demonstrated the usefulness of a scientific approach for the study of industrial archaeology heritage with the aim to contribute to its conservation and restoration. Full article

This study investigates the comparison of the Raman signatures of different phases used in underglaze, inglaze and overglaze decors of selected European, Chinese and Japanese porcelains and enameled metalworks, which are particularly representative of technological developments in enameling. Specifically, the article deals with the main structural types or host networks (corundum/hematite, spinels, zircon, cassiterite, pyrochlore, apatite, sphene, etc.) used for colored enamels on porcelain, earthenware or metal rather than considering all types of pigments and opacifiers. According to the results, Raman microspectroscopy allows identifying of the fingerprint spectra of milestone technologies and represents a simple and rapid tool for detecting copies. Particular attention is paid to the information deduced from the examination of the associated ‘background’ and signatures from electronic transitions induced by uncontrolled traces or voluntary addition of rare earths (luminescence). The relationship between the grinding procedure and Raman signature is also discussed. Full article

Two masterpieces of the Qing Dynasty (1644–1912 CE), one in gilded brass (incense burner) decorated with cloisonné enamels stylistically attributed to the end of the Kangxi Emperor’s reign, the other in gold (ewer offered by Napoleon III to the Empress as a birthday present), decorated with both cloisonné and painted enamels bearing the mark of the Qianlong Emperor, were non-invasively studied by optical microscopy, Raman microspectroscopy and X-ray microfluorescence spectroscopy (point measurements and mapping) implemented on-site with mobile instruments. The elemental compositions of the metal substrates and enamels are compared. XRF point measurements and mappings support the identification of the coloring phases and elements obtained by Raman microspectroscopy. Attention was paid to the white (opacifier), blue, yellow, green, and red areas. The demonstration of arsenic-based phases (e.g., lead arsenate apatite) in the blue areas of the ewer, free of manganese, proves the use of cobalt imported from Europe. The high level of potassium confirms the use of smalt as the cobalt source. On the other hand, the significant manganese level indicates the use of Asian cobalt ores for the enamels of the incense burner. The very limited use of the lead pyrochlore pigment (European Naples yellow recipes) in the yellow and soft green cloisonné enamels of the Kangxi incense burner, as well as the use of traditional Chinese recipes for other colors (white, turquoise, dark green, red), reinforces the pioneering character of this object in technical terms at the 17th–18th century turn. The low level of lead in the cloisonné enamels of the incense burner may also be related to the use of European recipes. On the contrary, the Qianlong ewer displays all the enameling techniques imported from Europe to obtain a painted decoration of exceptional quality with the use of complex lead pyrochlore pigments, with or without addition of zinc, as well as cassiterite opacifier. Full article

Fragments of decorated floor tiles were retrieved from the Akko Tower shipwreck, Israel. Most tiles were made of bright brown fired clay with a white glaze decorated with colored stenciled motifs (Type A); and others consisted of a red-brown fired clay body, coated with a brown pigment covered with transparent brown glaze (Type B). This study aimed to characterize the two tile types; to reveal information concerning the manufacturing process; and to determine the origin of their raw material. A multidisciplinary approach was used, including light microscopy, SEM-EDS, electron probe microanalysis with wavelength-dispersive X-ray spectroscopy (EPMA-WDS), XRD, Raman spectroscopy, and time-of-flight secondary ion mass spectrometry (TOF-SIMS) analyses. The characterization of both tile types demonstrated the use of different raw materials. The Type A tiles were covered with tin-opacified majolica glaze and colored with various mixtures of pigments. The blue color was due to pigment rich in cobalt; the yellow color was due to Naples yellow and lead-tin yellow I minerals; and the green, orange, and brown colors were all prepared by mixing the Naples yellow pigment with different minerals. These majolica glaze tiles were probably manufactured in Sicily. The brown coating of the Type B tiles was due to pigment rich in lead and iron minerals. These tiles were produced with different manufacturing processes, and apparently made in France. Full article

A selection of 15 Chinese painted enameled porcelains from the 18th century (Qing dynasty) was analyzed on-site by mobile Raman and XRF microspectroscopy. The highly prized artifacts are present in the collections of the Musée du Louvre in Paris and Musée Chinois at Fontainebleau Castle in France. In the painted enamels, pigments such as Naples yellow lead pyrochlore, hematite, manganese oxide and carbon and opacifiers such as lead arsenates were detected. The glassy matrices of the enamels mainly belonged to lead-rich and lead-alkali glass types according to the Raman spectra obtained. The glaze and body phases of the porcelain artifacts were also analyzed. The detection of lead arsenate apatite in some of the blue enamels was significant, indicating the use of arsenic-rich European cobalt ores (smalt) and possibly mixing with Asian cobalt. This characteristic phase has also been identified in French soft-paste porcelains and glass decor and high-quality Limoges enamels from the same period. Based on the shape of the Raman scattering background, the presence of colloidal gold (Au° nanoparticles) was identified in red, orange and pink enamels. Different types of Naples yellow pigments were also detected with Sb-rich, Sn-rich and mixed Sb–Sn–(Zn, Fe?) compositions in the yellow enamels. The results were compared to previous data obtained on Chinese cloisonné and painted enameled metalware and Limoges enamels as well as French enameled watches. Full article

A selection of 10 Chinese enamelled metal wares dating from the 17th–18th centuries (Qing Dynasty) was analysed on-site by mobile Raman microspectroscopy. These wares display cloisonné and/or painted enamels and belong to the collections of Musée du Louvre in Paris and Musée Chinois at the Fontainebleau Castle in France. Pigments (Naples yellow lead pyrochlore, hematite, manganese oxide etc.), opacifiers (fluorite, lead arsenates) and corresponding lead-based glassy matrices were identified. One artefact was also analysed by portable X-ray fluorescence spectrometry (pXRF) in order to confirm the Raman data. In some of these metal wares, it is suggested that cassiterite was unpredictably used as an opacifier in some parts of the decor. The results are compared to previous data obtained on Chinese cloisonné and Limoges enamels as well as recent data recorded on painted enamelled porcelains of the Qing Dynasty. Lead arsenate apatite detected in some of the 17th–18th century blue enamelled decors is related to the use of arsenic-rich European cobalt ores, as also characterized in French soft-paste porcelain and glass decors and high-quality Limoges enamels for the same period. However, lead arsenate could then also have been deliberately used for white opacification. The specific Raman signature displaying the shape of the Raman scattering background indicates the presence of colloidal gold (Au° nanoparticles) in red to violet enamelled and cloisonné areas. At least three types of Naples yellow lead pyrochlore pigments identified with Sb-rich, Sn-rich and mixed Sb–Sn–(Zn, Fe?) compositions prove the use of European pigments/recipes. Full article