Search Results (7)

In the Roman Empire, lead tags were used for various purposes, one of which was to label textiles that needed cleaning, repairing or dyeing. So far, these tesserae have been found at over 90 sites in 13 Roman provinces. The cities of Siscia and Carnuntum in Pannonia Superior have the highest number of finds. In 2011, a Roman cesspit was excavated in the civil city of Carnuntum and dated to the mid-2nd century CE. The latrine contained household and food waste, human faeces, pottery shards, pollen, lime, amber and 179 lead tags. The tags bear inscriptions consisting of personal names, prices, and abbreviations of terms relating to garments, colours and services such as cleaning, mending, repairing, fulling, fumigating, perfuming, dyeing, and redyeing. The findings of Roman textiles unearthed in Carnuntum are too degraded to allow a successful dye analysis to be carried out. Therefore, the inscriptions are important sources for drawing conclusions about dyeing materials and techniques. This information was supplemented by ancient written sources as well as archaeobotanical finds of dye plants and dye analyses of archaeological textiles found in Central Europe dating from the same period or earlier. Full article

The Rotunda in Thessaloniki, Greece, preserves in its interior a magnificent wall mosaic assemblage of unique inspiration and beauty. Thirty-six (36) glass tesserae, blue, green, yellow, brown, black, gold and silver in color, were examined for the first time via UV-Vis reflectance spectroscopy, scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) and X-ray diffraction (XRD) analysis, in order to investigate the base glass composition, and their technological and morphological features. Despite the heterogeneity observed in the glass composition, the results indicated similarities with other Early Christian and Byzantine wall mosaics in the use of colorants, opacifiers and decolorizers. Cobalt, copper, iron and manganese along with lead and tin compounds are responsible for the blue, green, yellow, brown and black colors. Tin-based opacifiers and bone ash contribute to the glass opacity. The use of different glass recipes and opacifiers in the Rotunda’s assemblage reflects the transition from the Roman glass tradition to the Byzantine glass production of the fourth and the fifth century in the eastern Mediterranean. Full article

Kriab-mirror tesserae are a type of lead-coated mosaic mirror found in most archaeological sites and antiquities dating back to the 18th century in central Thailand. The need for restoration work has prompted the search for alternative mirrors with similar characteristics to the ancient ones. Prototypes of alternative lead-coated mirrors were successfully used to restore a variety of archaeological sites and artifacts, demonstrating their potential application in heritage conservation and restoration work. We investigated the selected ancient Kriab samples in terms of their composition in both glass and reflective coating layers, as well as the chemical and mechanical characterization of the selected alternative Kriab mirrors. We employed a standard lab-shear test, which proved difficult to evaluate due to failure not occurring between the glass-to-metal interfaces. However, a modified lab-shear specimen setup was used to elucidate the peel-off bonding behavior of the lead-to-glass interface. Additionally, we measured the L*, a*, and b* values in the CIE-Lab standard, which exhibited variations for each colored Kriab mirror. The %reflectance of the selected ancient and alternative Kriab mirrors was highly similar when lower than a high %reflectance of a standard silvering mirror. Thai professional conservators have embraced the use of alternative Kriab mirrors in restoration projects as a replacement for old Kriab mirrors, as they are more compatible in terms of color and avoid the excessive brightness of silvered colored mirrors. However, the weathering durability of the alternative mirrors was poor due to the leaching of alkaline and lead ions caused by hydrolytic attack on the poor chemical stability separated phase. Overall, our research provides valuable insights into the properties and qualities of both ancient and alternative Kriab mirrors, which will be useful in the further development of mirrors with more resembling properties or even more environmentally friendly Kriab mirrors and their potential applications in restoration work in Thailand and archaeological sites in Asia. Full article

This study aims at the characterisation of red and orange glass tesserae from the 4th-century Roman villa of Noheda (Spain). Due to the limited number of analyses available for such ancient materials, many questions remain unanswered about the production processes in the Roman period. Six samples were chosen for their hue variations, including two samples showing banded patterns of red and orange. Differences in copper speciation were investigated by X-ray absorption spectroscopy and compared with colour and compositional variations obtained by EPMA. The shapes and sizes of colouring crystals could be investigated using scanning and transmission electron microscope imaging. The brown-red colour is due to metallic copper nano-particles and corresponds to a low-copper and low-lead group usually described in the literature. The orange samples and bands are coloured by copper oxide $\mathrm{C}{\mathrm{u}}_2\mathrm{O}$ nanoparticles with remaining Cu⁺ in the glass and have greater contents of Cu. Compositional analyses reveal that the same base glass is used in the red and orange bands with additions of Cu, Sn, Pb and probable Fe. Furthermore, based on our results and on the literature review, a high-copper low-lead group of glasses highlights the variability of compositions observed in cuprite colours. Full article

The present study focuses on manganese-containing inclusions identified in late-Antique glass tesserae, light brown/amber and purple in colour, from Padova (Italy), in order to clarify the nature of these inclusions, never identified in glass mosaics until now, and provide new insights on the production technologies of such kinds of tesserae. Multi-methodological investigations on manganese-containing inclusions were carried out in this work by means of optical microscopy (OM), scanning electron microscopy (SEM), micro-X-ray diffraction (micro-XRD), electron backscattered diffraction (EBSD), electron microprobe (EMPA), and micro-Raman spectroscopy. The combination of analytical results shows that inclusions are crystalline, new-formed phases, mainly composed of manganese, silica and calcium, and are mineralogically ascribed as a member of the braunite-neltnerite series, with unit-cell parameters closer to those of neltnerite. However, the low Ca content makes such crystalline compounds more similar to braunite, in more detail, they could be described as Ca-rich braunite. The occurrence of such crystalline phase allows us to constrain melting temperatures between 1000 and 1150 °C, and to hypothesize pyrolusite, MnO₂, as the source of manganese. In addition, it is worth underlining that the same phase is identified in tesserae characterised by different colours (light brown/amber vs purple due to different manganese/iron ratios), glassy matrices (soda-lime-lead vs soda-lime) and opacifiers (cassiterite vs no opacifier). This suggests that its occurrence is not influenced by the “chemical environment”, revealing these manganese-containing inclusions as a new potential technological marker. Full article

Calcium antimonate (in the hexagonal or cubic form) dispersed in the glass matrix is an artificially synthesized phase commonly documented as opacifier for white glasses during the Roman period. Glasses of this type occasionally contain variable amounts of lead oxide. There is no consensus about the origin and role of the lead component in white glasses, whether it was functional to modify the workability of the glass and/or to help the precipitation of the particles, or whether it was an unintentional pollutant introduced with the raw materials. A group of lead and lead-free white mosaic tesserae from the fourth-century CE villa of Noheda in Spain were analyzed by differential scanning calorimetry (DSC) and high temperature X-ray diffraction (HTXRD) to evaluate the impact of variable amounts of lead oxide in the precipitation of calcium antimonate on the viscosity of the glass. The analyzed glasses show thermal events that have been related to the composition of the glass via multicomponent linear regression model. CaSb₂O₆ and Ca₂Sb₂O₇ formed in the glass during the cooling phase and the glass was not reheated. Lead oxide influences the thermal behavior of the glass, lowering the onset temperatures of all the events, implying a more cost-effective production process. We propose that lead was added intentionally or that lead-bearing raw materials were selected specifically by the ancient glass artisans. Full article

Excavations at the Roman villa of Noheda (Spain) revealed the remains of an exceptionally elaborate fourth-century floor mosaic that contains a surprisingly large number of glass tesserae, representing a broad spectrum of colors. This paper presents the results of the chemical (LA-ICP-MS) and microstructural analyses (SEM-EDS, XRPD) of 420 glass tesserae from these mosaics. The high number of data allowed us to establish the compositional variability and to elucidate questions of supply in relation to a large-scale artistic campaign. The tesserae from Noheda were almost exclusively made from recycled mixed Roman Mn and Sb base glass, thus demonstrating that recycling of Roman base glasses was common practice in the fourth century, occurring on a near industrial scale. It also suggests that the workshops specializing in the production of mosaic tesserae might have been in the western Mediterranean. A limited number of coloring and opacifying additives (Mn, Co, Cu, Sb, Pb) were identified, which resulted in a wide range of hues. These were differentially associated with various trace elements, which implies the use of different raw materials. A sub-set of red, green, and orange tesserae reflect distinct base glass characteristics as well as coloring technologies that point to an Egyptian provenance. Full article