Roman Glass Research Articles

Vidrios romanos de Bracara Augusta (Portugal): Análisis Arqueométrico = Roman glass from Bracara Augusta (Portugal): Archaeometric analysys

In this work Roman glass from Bracara Augusta, nowadays Braga (Portugal), were studied through their chemical composition, analyzing the major, minor and trace constituents using plasma-mass spectrometry (ICP-MS). The obtained data were statistically analysed, with the following statistical methodologies: (i) various univariate analyses and (ii) several multivariate analyses which gave rise to a sample classification using hierarchical classification and by multiple discriminant analyses. Results concluded that, while all the glass samples showed a similar composition in terms of major components, there were some significant differences in these and in the minor components that allowed their classification. Furthermore, discriminant analysis helped to establish groups based on the dating of the glass and include undated samples in the previous stated groups.

Thin films composed of Ag nanoclusters dispersed in TiO2: Influence of composition and thermal annealing on the microstructure and physical responses

Noble metal powders containing gold and silver have been used for many centuries, providing different colours in the windows of the medieval cathedrals and in ancient Roman glasses. Nowadays, the interest in nanocomposite materials containing noble nanoparticles embedded in dielectric matrices is related with their potential use for a wide range of advanced technological applications. They have been proposed for environmental and biological sensing, tailoring colour of functional coatings, or for surface enhanced Raman spectroscopy. Most of these applications rely on the so-called localised surface plasmon resonance absorption, which is governed by the type of the noble metal nanoparticles, their distribution, size and shape and as well as of the dielectric characteristics of the host matrix. The aim of this work is to study the influence of the composition and thermal annealing on the morphological and structural changes of thin films composed of Ag metal clusters embedded in a dielectric TiO2 matrix. Since changes in size, shape and distribution of the clusters are fundamental parameters for tailoring the properties of plasmonic materials, a set of films with different Ag concentrations was prepared. The optical properties and the thermal behaviour of the films were correlated with the structural and morphological changes promoted by annealing. The films were deposited by DC magnetron sputtering and in order to promote the clustering of the Ag nanoparticles the as-deposited samples were subjected to an in-air annealing protocol. It was demonstrated that the clustering of metallic Ag affects the optical response spectrum and the thermal behaviour of the films.

Roman and late-Roman glass from north-eastern Italy: The isotopic perspective to provenance its raw materials

In this study, the strontium, neodymium and oxygen isotopic composition of Roman (1st–3rd century AD) and late-Roman glass (4th–6th century AD) from Adria and Aquileia, two of the most important archaeological sites of north-eastern Italy, is discussed.The majority of glass analysed, independent from age, shows values of strontium isotope ratios close to that of modern seawater, indicating that the source of lime in the glass was marine shell, and likely coastal sands were used in its production. The Nd signature of all late-Roman glasses from Aquileia and of the majority of the Roman ones from Adria, independent from their chemical composition, is homogeneous and higher than −6 εNd, supporting the hypothesis of an eastern Mediterranean origin, probably located on Syro-Palestinian coast. However, the composition of late-Roman samples with HIMT signature, with lower 87Sr/86Sr values correlated to higher contents in Fe2O3, TiO2, MgO and lower contents in CaO, suggests an area of origin for this glass on the Egyptian coast. In addition, the different Nd signatures of two Adria Roman glasses (εNd < −7) suggest their primary production in western Mediterranean. Oxygen isotopes proved to be a further diagnostic method to discriminate natron and soda plant ash glass, and different silica sources, in the case of the soda plant ash glass. The combination of isotopic and chemical data supports the hypothesis of an eastern Mediterranean origin for late-Roman glass, which may be produced in few primary workshops on the Syro-Palestinian and Egyptian coast, although not necessarily in the same ateliers as have been identified so far. In the case of the Roman glass investigated, although the majority of data suggests an eastern Mediterranean origin, on the basis of Nd isotopes and chemical compositions, the existence of other primary glass producers located in the western Mediterranean can be suggested.

Roman coloured glass in the Western provinces: The glass cakes and tesserae from West Clacton in England

A collection of tesserae and two fragments from rounded cakes of coloured glass, probably dating to the 2nd century AD, were found at West Clacton Reservoir, Essex, in the UK, by Colchester Archaeological Trust. A selection of the finds were analysed using SEM-EDS and ICP-MS. This paper provides data on the composition of the different glass colours and discusses how each colour was made. Colourants and opacifiers were added to a base glass, most often one of the transparent, naturally coloured (blue-green) natron glass types widely available at the time, but there appear to be preferences in the type of base glass used for certain colours, which affects the type of antimonate opacifier precipitated. Possible reasons for using different types of base glass to make strongly coloured Roman glass are discussed.

‘A green thought in a green shade’; Compositional and typological observations concerning the production of emerald green glass vessels in the 1st century A.D.

The results of a programme of compositional analysis on a series of emerald green glass vessels of known form and date suggest that emerald green vessels have distinct characteristics that set them apart from most contemporary glasses. These specific compositional peculiarities presented here will be evaluated in the context of the varieties of vessel forms produced in the colour. In the light of our findings we will suggest a number of ways forward in the understanding of the structure of the early Roman glass industry.

Caracterización y estado de conservación de vidrios tardorromanos del Museo Arqueológico Regional de Madrid procedentes de las necrópolis de Cubas de la Sagra

A set of late Roman glasses found in the graveyards of Cubas de la Sagra and nowadays conserved in the Archaeological Regional Museum of Alcalá de Henares (Madrid) has been characterized. The glass set is from the Camino de Santa Juana site, located in the South of the Community of Madrid. The objectives were, on the one hand, to determine the chemical composition and the chromophores responsible for the the glasses colour, and, on the other hand, to evaluate their conservation state to select the best preventive conservation strategy for their deposit or exhibition in the museum. For the first part, 14 samples from both graveyards were analyzed. For the second part, samples of soil near the glasses were studied to determine pH, mineralogical phases and influence on the glasses deterioration. The research was carried out by using conventional techniques: binocular microscope, X-ray fluorescence spectrometry, X-ray diffraction, field emission scanning electron microscopy equiped with X-ray energy dispersive spectrometry and visible spectrophotometry. The results allowed the glasses archaeometric contextualization in the whole late Roman ensemble of glasses of the Iberian Peninsula that have been analyzed by X-ray fluorescence and X-ray energy dispersive spectrometry up to now.

Changes in glass consumption in Pergamon (Turkey) from Hellenistic to late Byzantine and Islamic times

We present compositional data for nearly 100 glass samples from Pergamon, western Turkey, spanning 1500 years from the Hellenistic to Late Byzantine and Islamic periods. The data shows the use of already-known Roman glass groups during the first half of the time frame, for imported vessels as well as locally worked glass. No compositional change is seen related to the introduction of glass blowing for either of the glass groups in use during this time. During the first half of the 1st millennium AD, two previously little-known boron- and alumina-rich compositional groups emerge. These glass groups, thought to be regionally produced, dominate glass compositions in Pergamon during the mid-to late Byzantine and Islamic periods, indicating a major shift in glass supply and a fragmentation of the economy into more regional units. Plant-ash glass, from the 9th century AD replacing mineral natron glass in the Levant, plays only a minor role in Byzantine and Islamic Pergamon.

Ennion, Master of Roman Glass: Further Thoughts

Ennion, Master of Roman Glass: Further Thoughts

Multianalytical characterization of Late Roman glasses including nanosecond and femtosecond laser induced breakdown spectroscopy

Nanosecond and femtosecond laser induced breakdown spectroscopy, X-ray fluorescence, ultraviolet-visible spectroscopy and laser induced fluorescence were combined for the analysis of Late Roman glasses.

Validation of the determination of the B isotopic composition in Roman glasses with laser ablation multi-collector inductively coupled plasma-mass spectrometry

The applicability of laser ablation multi-collector inductively coupled plasma-mass spectrometry (LA-MC-ICP-MS) for the determination of the B isotopic composition in Roman glasses was investigated. The δ11B values thus obtained provide information on the natron flux used during the glass-making process. The glass samples used for this purpose were previously characterized using pneumatic nebulization (PN) MC-ICP-MS. Unfortunately, this method is time-consuming and labor-intensive and consumes some 100mg of sample, which is a rather high amount for ancient materials. Therefore, the use of the less invasive and faster LA-MC-ICP-MS approach was explored. In this work, the results for 29 Roman glasses and 4 home-made glasses obtained using both techniques were compared to assess the suitability of LA-MC-ICP-MS in this context. The results are in excellent agreement within experimental uncertainty. No difference in overall mass discrimination was observed between the Roman glasses, NIST SRM 610 reference glass and B6 obsidian. The expanded uncertainty of the LA-MC-ICP-MS approach was estimated to be <2‰, which is similar to that obtained upon sample digestion and PN-MC-ICP-MS measurement.

HERODIAN INNOVATION: The Glass Industry

When timing, location, resources, experience, and inspiration coincide, a phenomenon can occur such as the invention of glass blowing and its impact on the development of the Roman glass industry. The impetus for this new industry came from Hellenistic glass production, particularly in Israel where Herod's personal relationship with Augustus assured economic, social, and political strength. The Herodian period is marked by creative energy, manifested in the technology of the time and demonstrated in remarkable advancements in the glass industry. New technology, originating in Jerusalem, spread so rapidly that it is difficult to track. This paper examines the late Hellenistic, Herodian and Augustan history of glass and how technical advancements coincided with improved Roman sea trade to transform glass making into a global industry. Earlier technical advancements had previously allowed greater production and lower prices, but it was the invention of glass blowing that truly revolutionized glass making.

Roman glasses coloured by dissolved transition metal ions: redox-reactions, optical spectroscopy and ligand field theory

A collection of Roman glass samples from Ancient Messene, Greece, was analysed non-destructively for colouring elements and non-colouring additives such as fining agents, opacifiers and decolourizers, by comparing the chemical composition with the observed optical spectra. The resulting information on ion speciation is important for the discussion of technological parameters such as the applied melting temperatures or the prevalent redox conditions. Speciation also helps to distinguish intentionally added dopants from impurities. This knowledge might be used in provenancing the raw materials. The Roman assemblage under study included purple coloured Mn3+-containing glasses, but also samples with high levels of colourless Mn2+. Manganese ions can either be considered a residue of recycling, or are indicative of an intentional addition, either as a fining or as a decolouring agent. Antimony oxide was either added as a fining agent, resulting in good quality transparent glasses, or as crystalline antimonates which act in glass mosaic tesserae as opacifiers. The much weaker molar extinction coefficient and the partial reduction of blue Cu2+ to colourless Cu+ explain why CuO is a weaker colouring agent than CoO. The colours of iron-bearing glasses range from light blue to green and from yellow to dark brown, reflecting a complex interplay between redox conditions and the presence of sulphur in the glass melt.Quantitative speciation of dopants will be reviewed on the basis of the ligand field theory. The different transition probabilities will be demonstrated on differently doped soda lime silicate glasses which were prepared for this purpose in the laboratory.

Characterization of colorants and opacifiers in roman glass mosaic tesserae through spectroscopic and spectrometric techniques

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 (Cu0) and Cu2O particles (cuprite) in red and orange tesserae, respectively. These results confirm the high technological level reached by the glassmakers of the Imperial Age. Copyright © 2014 John Wiley &amp; Sons, Ltd.

Copper and antimony isotopic analysis via multi-collector ICP-mass spectrometry for provenancing ancient glass

Variations in the isotopic composition of Cu and Sb as determined using multi-collector ICP-mass spectrometry (MC-ICPMS) have been investigated as a proxy for provenancing ancient glass. Cu and Sb were added during the manufacturing of ancient (pre-Roman and Roman) glass to obtain colour and opacity. In previous work, the analytical methodology for sample digestion and isolation of Sb preceding isotopic analysis via multi-collector ICP-MS was developed. Although applications of Cu isotopic analysis can be found in the literature, this approach has not been used for provenancing glass raw materials yet. Therefore, the protocols for digestion and Cu isolation were optimized and validated, relying on the use of both an in-house multi-elemental standard and NIST SRM 610 glass reference material. The methods for Sb and Cu isotopic analysis were subsequently applied to a series of late Bronze Age Mesopotamian–Egyptian to Hellenistic–Roman glasses. Results obtained show that the isotopic composition of Cu, expressed as δ65Cu, varies from −1.9 to −0.2‰, thus covering a range of approximately 2‰. Unfortunately, the use of Cu isotope ratios to characterize raw materials used in glass manufacturing is complicated by the fact that Cu ores from within a single deposit can exhibit a similar range in δ65Cu values, certainly for co-existing Cu sulfides and oxides. Sb in stibnite ore, on the other hand, only shows a variance in isotopic composition of ∼10 e units (or 0.1‰), but Sb isotopic analysis offers more potential to pinpoint the location of an antimony source used in antiquity.

Composition data of a large collection of black-appearing Roman glass

Jewels and tableware made of black-appearing glass were popular in the Roman Empire. Compositional changes (due to modifications in glassmaking technology and use of raw materials) over the period considered (1st-5th century AD) have been investigated on a large number of samples originating from various archaeological excavations in Europe, Northern Africa and the Near East. In the course of this work, over 400 samples of Roman glass, the greatest part of them deeply coloured glass fragments, were embedded into acrylic resin and mechanically ground and polished in order to obtain flat surfaces of unaltered glass. The samples were analysed with scanning electron microscopy/energy dispersive X-ray spectroscopy and the quantification was performed by using a standard-less ZAF software. The trace elements contained in a selection of glass samples were determined via laser ablation-inductively coupled plasmamass spectrometry. The data collected in this study show that from about 150 AD a change in the black glass production process occurred, involving coloration of raw glass made with iron in the secondary workshops. Furthermore, from the 4th century AD on we can observe a change in the type of raw glass used, while the colouring process was maintained. The main aim of this paper is to provide glass scholars with the analysis results, as reference and comparison for further studies.

Development of a Novel Method for Unraveling the Origin of Natron Flux Used in Roman Glass Production Based on B Isotopic Analysis via Multicollector Inductively Coupled Plasma Mass Spectrometry

The provenance of the flux raw material used in the manufacturing of Roman glass is an understudied topic in archaeology. Whether one or multiple sources of natron mineral salts were exploited during this period is still open for debate, largely because of the lack of a good provenance indicator. The flux is the major source of B in Roman glass. Therefore, B isotopic analysis of a sufficiently large collection and variety (origin and age) of such glass samples might give an indication of the number of flux sources used. For this purpose, a method based on acid digestion, chromatographic B isolation and B isotopic analysis using multicollector inductively coupled plasma mass spectrometry was developed. B isolation was accomplished using a combination of strong cation exchange and strong anion exchange chromatography. Although the B fraction was not completely matrix-free, the remaining Sb was shown not to affect the δ(11)B result. The method was validated using obsidian and archaeological glass samples that were stripped of their B content, after which an isotopic reference material with known B isotopic composition was added. Absence of artificial B isotope fractionation was demonstrated, and the total uncertainty was shown to be <2‰. A proof-of-concept application to natron glass samples showed a narrow range of δ(11)B, whereas first results for natron salt samples do show a larger difference in δ(11)B. These results suggest the use of only one natron source or of several sources with similar δ(11)B. This indicates that B isotopic analysis is a promising tool for the provenance determination of this flux raw material.

Deeply colored and black-appearing Roman glass: a continued research

In the context of archaeological and historical assessment of Roman black-appearing glass, the chemical and physical characterization of a large collection of samples originating from various areas of the Roman Empire has been gathered over the past years to (i) verify whether a minor segment of the overall Roman glass production can help in determining possible diachronic changes in Roman imperial glass production (1st century AD – 5th century AD) and (ii) reveal regional compositional differences. In this paper, the latest results on the chemical composition of an additional 44 black-appearing Roman glass samples are presented, together with general conclusions based upon the entire compositional dataset of over 400 analyzed black glass samples. The results show that the Roman black glass is obtained through several glass compositions with a specific chronological, geographical and typological distribution.

Trace Element Analysis in Provenancing Roman Glass‐Making

In this study, the use of trace elements as a provenance indicator for Roman natron glass is evaluated. Suitable glass‐making sand raw materials are analysed for their trace elemental composition and compared to glass from known production centres. It is shown that the combined use of Nd isotopic and trace element analysis can be efficient for the provenancing of Roman glass. Trace elements associated with (de)colourants of glass are only present in small concentrations in glass‐making sands. Background levels introduced to the glass by the sand raw material are defined and a lower threshold for the concentrations influenced by recycling is determined.

Composition, Production and Procurement of Glass at San Vincenzo al Volturno: An Early Medieval Monastic Complex in Southern Italy

136 glasses from the ninth-century monastery of San Vincenzo and its workshops have been analysed by electron microprobe in order to situate the assemblage within the first millennium CE glass making tradition. The majority of the glass compositions can be paralleled by Roman glass from the first to third centuries, with very few samples consistent with later compositional groups. Colours for trailed decoration on vessels, for vessel bodies and for sheet glass for windows were largely produced by melting the glass tesserae from old Roman mosaics. Some weakly-coloured transparent glass was obtained by re-melting Roman window glass, while some was produced by melting and mixing of tesserae, excluding the strongly coloured cobalt blues. Our data suggest that to feed the needs of the glass workshop, the bulk of the glass was removed as tesserae and windows from a large Roman building. This is consistent with a historical account according to which the granite columns of the monastic church were spolia from a Roman temple in the region. The purported shortage of natron from Egypt does not appear to explain the dependency of San Vincenzo on old Roman glass. Rather, the absence of contemporary primary glass may reflect the downturn in long-distance trade in the later first millennium C.E., and the role of patronage in the “ritual economy” founded upon donations and gift-giving of the time.

GOLD GLASS TESSERAE SAID TO BE FROM THE ROMAN VILLA SITE AT SOUTHWICK, WEST SUSSEX

This paper seeks to characterise through elemental analysis some unusual gold glass tesserae said to have been found at a Roman villa site in Southwick, West Sussex. The site is no longer accessible, being underneath a Methodist chapel, but it has been excavated, to some extent, on several occasions. Glass tesserae are not common in a British setting but they are by no means unusual in Roman mosaics. Gold glass tesserae, however, in which gold leaf is sandwiched between two layers of glass, are very unusual: fewer than twenty such tesserae are known from Roman Britain and the seven examples from Southwick make up the largest single group. However, the provenance of these Southwick tesserae remains doubtful and so they were analysed and compared to gold glass tesserae from Roman London to try and establish whether they are compositionally related to typical Roman glass. For comparative reasons, the handful of coloured glass tesserae from Southwick were also analysed. Our results suggest that the tesserae said to be from Southwick are anomalous in relation to the other material and cannot be assigned to the Roman period.