Search Results (27)

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

The mosaic tesserae that are the topic of this study were found during an archeological excavation in a Roman villa at Aiano, in the municipality of San Gimignano, Tuscany (Italy). Many thousands of tesserae were found in the site in many different stratigraphic units (US). For this study, 392 tesserae mainly from three US (US 1095, US 5010 and US 5015 being the most consistent ones) were selected for non-invasive analyses. They might be tesserae coming from different places, collected to be reused or melted down to create new glass objects. The characterization of the tesserae, divided in various groups depending on their color, is an important tool in evaluating their compositional homogeneity/inhomogeneity. The presence of certain markers, such as the opacifiers based on Sb or Sn, could be helpful also in approximately dating the tesserae, since, as reported in the literature, various opacifiers were used in different periods. A well-established diagnostic protocol, based only on non-invasive techniques, allowed us to study a large number of tesserae, which certainly did not derive from a single mosaic and could have been of very different ages, compositions and origins. This procedure has proven to be a winning tool for this aim. Full article

This work illustrates the results of an archaeometric investigation performed on 29 stone tesserae collected from 2021 to 2024 during the restoration campaigns of three mosaic floors at Praedia Iuliae Felicis in Pompeii (Campania, Italy). The tesserae were studied through a micro-analytical approach using Polarized Optical Microscopy (POM), Scanning Electron Microscopy (SEM) with Energy-Dispersive X-ray Spectroscopy (EDS) and Electron Probe Micro-Analyzer with Wavelength-Dispersive Spectroscopy (EPMA-WDS). The aim of the study was to determine the petro-chemical features of the mosaic tesserae and to obtain information about the provenance of the raw materials. The research highlights the use of different types of stone, such as volcanic and sedimentary, of probable local provenance. A single marble tessera was also recognized. In addition, the archaeometric study allowed a better knowledge of the executive technique and contributed to orienting the technical choices of the restoration. Indeed, a complementary study of conservation state of the three mosaic floors was conducted with the aim of better defining strategies for conservation and restoration, paying attention to the compatibility and to the interaction of the restoration products with the characteristics of the raw materials. Full article

Since the Hellenistic period, preparatory drawings known as sinopiae were employed as guidelines for mosaicists in creating mosaics. The sinopiae served as the basis for style and content, facilitating the placement of colored tesserae in the supporting mortar. The technology of the mosaic and pigments used reflect the capacity of the mosaic workshop and its master. This work explores a polychrome sinopia that was found under a Byzantine mosaic of an Armenian Chapel in Jerusalem, by a multi-analytical characterization of mineralogical and chemical properties. The composition of the pigments in the black and red areas of the sinopia include carbon black and red ochre, respectively, utilized in the fresco technique. Since colored tesserae are placed in wet mortar, it can be deduced that mosaicists worked together with painters during the executionary steps. This has corresponding implications for historical and artistic specializations at mosaic workshops, with deeper understanding of mosaic production processes. This research also highlights the importance of studying sinopiae under floor mosaics, which is a source of information on the pigments, paintings techniques, and the people who executed the work, all embedded in mortar which is well protected below the stone tesserae. Full article

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

The archaeological site of villa Horta da Torre in Portugal reveals distinctive architectural features within the context of Roman villae in Hispania. Notably, the triclinium was designed with an artificial cascade originating from a double apse wall, and the walls were adorned with mosaic tessellae panels and marble skirting. During the Roman era, the surrounding area belonged to the former province of Lusitania, with Augusta Emerita serving as its capital. This study examines 11 mortar samples from various contexts and functions, such as masonry, preparatory, render, and opus signinum mortars. A set of complementary analytical techniques was employed to determine the textural and mineralogical compositions of the mortars. The aim was to gain insights into the production techniques and the selection of raw materials within the geological context of this rural construction. It was observed that the processing of raw materials and production techniques did not always adhere to the rules of Vitruvius. A comparison with other villas revealed comparatively less meticulous attention to sand selection and precise layering for mural painting. Nevertheless, it was noted that in preparatory layers for the supranucleus and nucleus tesserae, ceramic pieces were intentionally added to improve the mortar. The binder used was calcitic lime, likely obtained from locally sourced limestone. The nature of aggregates is diversified but consistent with the local geological provenance within a radius of less than 3 km, in accordance with two sand exploration sites. This research aligns with the United Nations’ 2030 Agenda for Sustainable Development, contributing specifically to SDG 11 and Target 11.4, which “aims to strengthen efforts to protect and safeguard the world’s cultural and natural heritage”. 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

The mosaic in the apse of the Church of S. Agnese fuori le mura in Rome represents one of the most important examples of the wall mosaics of the Roman Middle Ages. Although it is associated with Byzantine figurative culture, no scientific study has addressed this important piece of Italian art history. One factor that has probably limited and created difficulties for its analysis is the poor legibility of the original parts, which are compromised by heavy restorations affecting the gold background, the faces of the two male side figures, and the lower band of the mosaic. The present work describes how multispectral imaging provided significant guidance in the preliminary identification of possible original areas in this ancient wall mosaic. Through an interdisciplinary approach, the art historical background and historical graphic documentation of known restorations supported the use of multispectral imaging to recognize original parts. The initial results of the lab analyses (SEM-EDS and EMPA) of supposed original tesserae validated the hypothesis made a priori thanks to multispectral acquisition, opening up new application possibilities for use of this noninvasive technique in the preliminary in situ identification of original parts in restored glass wall mosaics. Full article

Glass can be considered a locus of meaning, a material which has been the repository of traditional knowledge and technological expertise for at least three millennia. The history of glass speaks of know-how, technological transitions, and contaminations of recipes for its manufacture, which have changed across the world over the centuries. As the amount of recovered glass from archaeological contexts is much lower compared to ceramic and metal finds, research has often considered glass as a rare material. Furthermore, glass production, in ancient times as in the present day, requires the use of selected raw materials and noticeable amounts of fuel, making reuse and recycling practices necessary to foster sustainability, from both an economical and an environmental perspective. Latin authors, such as Juvenal and Martial, reported buyers of broken glass in Imperial Rome, presumably destined for recycling. Archaeometry has also provided data that allow, today, to clarify different aspects related to production cycles, uses and reuses of a material that, starting from the Roman age, became as common as modern plastics. From beakers and goblets reused with different purposes to mosaic tesserae detached for making new mosaics or to be refused and employed as “pigments” for colouring glass, this paper aims to provide an overview of reuse and recycling practices of ancient glass through a discussion of selected case studies from Roman to Middle Ages, showing how the cycle of this material can be framed as an actual example of sustainable circular economy in the past. Full article

The church of S. Mary of the Admiral in Palermo, known as “La Martorana” and very famous for its Byzantine mosaics, has been a World Heritage site since 2015. The mosaic system of the church includes several groups of figures and scenes from the life of the Virgin Mary. From the western part of the ancient church only two mosaics survive, detached from their original position, and are now located in two internal chapels. On the occasion of several restoration works, these two mosaic panels were investigated with non-invasive techniques, in order to provide diagnostic support to the restoration and consolidation interventions. The investigations were aimed at detecting any air pockets that could cause the detachment of the tesserae or of possible differences between cement mortars under the tesserae. For this purpose, the integrated use of two non-invasive techniques namely infrared thermography (IRT) and ground penetrating radar (GPR) was considered. The joint analysis of IRT and GPR data allowed the interpretative uncertainties inherent in each technique to be reduced. Furthermore, for both techniques differentiated analyses were performed for layers at different depths under the mosaic surface. The results of these analyses were found to be more reliable regarding GPR data, compared to infrared thermography, the latter being more influenced by the reflectivity of the tesserae. However, the results partially confirmed the restorers’ diagnosis, also allowing the identification of further critical areas that could be affected by deterioration or compositional differences in the layers supporting the mosaics Full article

The archaeological excavations at Villa San Pancrazio (Taormina, Italy) are bringing to light a vast Roman-Imperial residential quarter featuring luxurious dwellings decorated with wall paintings and mosaic floors, pointing it out as one of the most significant archaeological sites of the city. The polychrome and black and white mosaics recovered date back to the middle Imperial period, during the 2nd century AD. This work deals with the first archaeometric investigations of the materials employed for the tesserae production with the aim of elucidating the mineralogical composition and obtaining analytical evidence that can contribute to extracting information related to their production technology. For that purpose, a non-invasive methodology, based on micro energy dispersive X-ray fluorescence (μ-EDXRF) spectrometry and Raman spectroscopy, was used to characterize a wide selection of stone, ceramic and glass tesserae. Chemometric tools were exploited to manage the large set of elemental data collected on black and white lithic samples, providing essential clues for the subsequent investigations. The results evidenced the employment of natural lithotypes (calcareous sedimentary, dolomitic and volcanic) local and imported, and also artificial materials, such as ceramic made firing magnesium-rich clays, soda-lime-silica glasses made with different opacifying and coloring agents (such as calcium antimoniate, cobalt and copper). Full article

The connection between Umayyad and Byzantine mosaic manufacture is a debated issue: on the one hand, Arab sources report that Umayyad caliphs received craftspeople and materials to adorn religious buildings from the Byzantine emperor; on the other hand, the reliability of these texts has long been disputed among scholars, and other possible influences have been hypothesised. Was early Islamic mosaic manufacture related to Byzantine tradition and to what extent? Were materials and artisans gathered from Byzantium and/or territories under the Byzantine control? Based on a multi-analytical approach, glass tesserae from Khirbat al-Mafjar, the Great Mosque of Damascus, and the Dome of the Rock have been analysed. Results speak of a tale of two legacies, demonstrating that, parallel to a continuity with the manufacture of glass tesserae in the late antique Levant—pointing, more specifically, to a re-use of materials from abandoned buildings—legacies other than Byzantine occurred. It emerged that Egypt definitively played a role in mosaic making during the Umayyad caliphate, acting as a supplier of skilled artisans and materials. Full article

The Antas site (SW Sardinia, Italy) is of fundamental cultural importance because it testifies the presence of Nuragic, Punic and Roman civilizations from the second millennium to the third century BC. This work focuses on the Punic and the Roman temples and aims to define their conservation state and provenance of construction materials through their minero-petrographic and physical-mechanical characterization. In addition, artificial geomaterials used in restoration works comprising a partial anastylosis and a consolidation intervention on the monument, were investigated to evaluate the aesthetic, petrographic and petrophysical compatibility with the original materials. The results indicate that Punic builders preferred to use a porous sandstone coming from at least few kilometres away from the site. By contrast, Roman builders opted for the use of the less porous and harder local metadolostones, more difficult to quarry and to hew but promptly available in the surrounding area. The Roman temple still preserves decorative architectural elements (as the Pronao threshold and the mosaic tesserae) whose source is definitely not local, suggesting the import of these materials. As regards artificial materials, a new material was found within the Punic temple consisting of a sandstone-like rock (i.e., lime based sandy-conglomeratic geomaterial) and characterized by higher mechanical strength and lower porosity. Full article

In recent years, the interest of institutions in land use has increased, creating the need to determine the changes in use through spatial-temporal and statistical analysis. This study analyzes the changes over the last 40 years, based on a cartography of landscape units obtained from the study of geo-environmental parameters in the Jerte Valley (Spain) with satellite images, Landsat 5 and 7. Subsequently, through the analysis of spatial patterns and diversity and fragmentation indices, and with the Fragstat software, the landscape was characterized from 1994 to the present. The results show that wooded areas decreased slightly, crops increased in altitude and major environmental disturbances (mainly forest fires) negatively affected the environmental mosaic. Land uses affect the landscape by developing larger tesserae (+5 ha), which are less fragmented (−0.15), but more isolated (0.12). This study demonstrates that landscape metrics can be used to understand changes in spatial pattern, help in decision making to implement appropriate management measures in the conservation of traditional land uses, and allow the maintenance of connecting areas between fragments to avoid the loss of natural corridors to increase landscape quality. Full article

Archaeometric studies on mosaics often concentrate only on glass tesserae, while comprehensive studies including both stone and glass tesserae are scarce; however, both types of tesserae can sometimes bring relevant data to elaborate archaeological knowledge on a studied mosaic. In this paper, a representative set of tesserae from a large polychrome Roman mosaic retrieved in Barcelona (NE Spain) is investigated using various methods. Most of the techniques were directly applied on samples prepared as petrographic thin sections (including polarized-light, cathodoluminescence and electron microscopies, and synchrotron through-the-substrate μX-ray diffraction). The results indicate that, from the ten sampled stone tesserae, there are (i) seven limestones, one of them identified as Alveolina limestone (early Eocene) from the southern Pyrenees (ii) two sandstones from Barcelona’s Montjuïc hill (Miocene) and, (iii) a Carrara white marble from the Apuan Alps (Italy). The profuse presence of tesserae of both local and imported materials with well-known uses in architecture, epigraphy, and sculpture could imply that tesserae were a by-product of their main use. Two different production technologies were identified for the three sampled glass tesserae. The concurrent use of antimony- and tin-based opacifiers is in agreement with the accepted archaeological chronology of the mosaic (4th century AD). Full article