The Production and Circulation of Carthaginian Glass Under the Rule of the Romans and the Vandals (Fourth to Sixth Century ad): A Chemical Investigation

Fifty‐seven glass samples from Carthage dating to the fourth to sixth century ad were analysed using the electron microprobe. The results show that these samples are all soda–lime–silica glass. Their MgO and K₂O values, which are below 1.5%, suggest that they were made from natron, a flux that was widely used during the Roman period. The major and minor elements show that these samples can be divided into four groups, three of which correspond to the late Roman period glass groups that were found throughout the Roman Empire: Levantine I, and ‘weak’ and ‘strong’ HIMT. Of particular interest is our Group 2, which is technologically and compositionally similar to HIMT glass and the CaO and Al₂O₃ values of which are similar to those of Levantine I. Glass of similar composition has been reported by several authors and is predominantly found dating from the late fifth to seventh century. This could represent a ‘new’ glass group; therefore further study is needed to determine its origin. Also, this study suggests that the Vandal invasion in North Africa did not disrupt the glass trade between Carthage and the Levantine coast.     

The So‐called Venetian Enamelled Copper Artworks of the Italian Renaissance: the Technology and Provenance of the Enamels—an Analytical Approach

The so‐called Venetian enamelled coppers are a group of objects produced in Italy during the 15th century. Up to now, about 300 objects have been recognized in private collections and in European and US museums. At the end of 19th century, a Venetian origin was suggested, but their provenance is still debated. In this study, the enamel compositions from 22 enamelled copper products from Italian and French collections have been analysed by invasive and non‐invasive techniques. A comparison of the results with Tuscan and Venetian glass databases reinforces the suggestion of a Tuscan (most probably Florentine) origin for these works of art.     

DISCOVERY,PRODUCTION AND USE OF TIN‐BASED OPACIFIERS IN GLASSES,ENAMELS AND GLAZES FROM THE LATE IRON AGE ONWARDS: A REASSESSMENT*

Tin‐based opacifiers (lead stannate yellow and tin oxide white) were first used in glass production for a short period in Europe from the second to the first centuries bc , and then again throughout the Roman and Byzantine Empires from the fourth century ad onwards. Tin oxide was also used in the production of Islamic opaque glazes from the ninth century ad , and subsequently in enamels applied to Islamic and Venetian glasses from the 12th century ad onwards. A selection of published analytical data for the tin‐opacified glasses, enamels and glazes is summarized, and the methods used in their production are reassessed. The phase transformations occurring when mixtures of lead oxide, tin oxide and silica are fired are investigated with high temperature X‐ray diffraction (XRD) using a synchrotron radiation source, and these results are used to explain the observed differences in the glass, enamel and glaze compositions. Possible reasons for the use of tin‐based opacifiers in the second to first centuries bc , and for the switch from antimony‐ to tin‐based opacifiers in the fourth century ad are suggested, and the possible contexts in which tin‐based opacifiers might have been discovered are considered. The introduction of tin‐opacified glazes by Islamic potters in the ninth century ad is discussed in terms of technological transfer or independent invention.     

Glass and glass production in the Oman peninsula in antiquity reconsidered – chemical and mineralogical investigation of sands

A batch of green‐ and amber‐coloured glass chunks and unguentaria dating from the first century CE was found in 2007 at Dibba al Hisn, a site on the Arabian Sea coast of the United Arab Emirates (UAE). Its elemental and isotopic composition revealed the glass to be of a previously unknown plant ash glass type, different from known contemporary Roman, Mesopotamian, and Indian glass. The Sr isotopic composition of the glass corresponds to locally available plants, pointing to the possible existence of a first‐century CE local glass production centre. To explore this possibility, sands from around the UAE were analysed to establish their suitability for glass making and correspondence with the Dibba finds. This paper presents the results of the elemental analysis of fourteen sands. The analysis, performed using inductively coupled plasma optical emission spectroscopy (ICP‐OES), revealed all sands to be rich in lime and alumina. X‐ray diffraction revealed the presence of calcite and other carbonate minerals, as well as antigorite and quartz. Comparison of the sand compositions to average first‐century CE non‐Roman glass found at Dibba showed them to be unsuitable as raw material for producing the glass of Dibba. The evidence thus identifies this glass batch as imported, contrary to what was suggested before. This paper also reviews the occurrence of thick‐walled unguentaria in the region.     

ROMAN WINDOW GLASS: A COMPARISON OF FINDINGS FROM THREE DIFFERENT ITALIAN SITES

Thirty‐three samples of window glass and five glass lumps coming from three Italian archaeological sites—the Suasa excavations (Ancona, settled from the third century bc to the fifth to sixth centuries ad ), the Roman town of Mevaniola (Forlì‐Cesena, settled from the Imperial Age up to the fourth century ad ) and Theodoric's Villa of Galeata (Forlì‐Cesena, settled from the sixth century ad onwards)—were analysed to track the changes in the chemical composition and manufacturing technology of window glass through the centuries. The aims of this study were: (1) to establish the origin of the raw materials; (2) to verify the chemical homogeneity among samples coming from different sites and/or produced using different techniques; and (3) to sort the samples into the compositional groups of ancient glass. The analysis of all the chemical variables allowed two groups to be distinguished: (a) finds from Mevaniola and Suasa; and (b) finds from Galeata. All the samples had a silica–soda–lime composition, but the analysis of minor elements—in particular, of Fe, Mn, and Ti—made it possible to split the samples into two groups, with the higher levels of these elements always found in the Galeata samples (HIMT glass). In conclusion, it can be asserted that the main differences between the samples are related to their chronology.     

The Chronology of Insiza Cluster Khami‐Phase Sites in South‐Western Zimbabwe: Compositional Insights from pXRF and Raman Analysis of Excavated Exotic Glass Finds

Fourteen glass beads and one glass fragment from Khami‐period (ad 1400–1830) sites of Danamombe, Naletale, Gomoremhiko, Nharire and Zinjanja, in Zimbabwe, were analysed by pXRF and Raman spectroscopy with the intention of correlating the results with associated radiocarbon dates. The results show that Zinjanja and an earlier part of the Danamombe stratigraphic context had Khami Indo‐Pacific beads (15th–17th centuries) corresponding with Torwa occupational layers. Other European beads and one bottle fragment [high‐lime, low‐alkali (HLLA) glass] dating from the 16th to the 19th centuries were confined to the top stratigraphic layers of Danamombe and Naletale, which coincide with the later Rozvi occupational layers. Gomoremhiko had one Mapungubwe–Zimbabwe bead series (13th–15th centuries), which suggests that it was probably earlier than the other sites. All European beads are made of soda–lime plant‐ash glass with high alumina, which makes them comparable with glass produced through the Mediterranean traditions in Southern Europe.     

Composition of the Lustre Pigment Used in the Production Of 13th Century AD Raqqa Lustreware from Syria

The very rare find of the relic of the original lustre pigment attached to the glazed surface of a sherd of 13th century ad Raqqa type lustreware from Syria has been analysed using a combination of analytical scanning electron microscopy (SEM), micro‐X‐ray diffraction (XRD) and Rutherford backscattering spectroscopy (RBS). The composition of the pigment relic inferred from these analyses is shown to match those of recipes for lustre production given in the early treatises by Jazbir Ibn Hayyan (c. ad 721–c. ad 815) and Abū'l Qasim (ad 1301). Similarities and differences between this 13th century ad Syrian pigment and pigments used in the ninth century ad in Iraq, in the 14th century ad in Islamic and Hispano‐Moresque Spain, and in the 16th century ad in Renaissance Italy are discussed.     

A COMBINED MULTI‐ANALYTICAL APPROACH FOR THE STUDY OF ROMAN GLASS FROM SOUTH‐WEST IBERIA: SYNCHROTRON μ‐XRF,EXTERNAL‐PIXE/PIGE AND BSEM–EDS

An integrated, multi‐analytical approach combining the high sensitivity of SR‐μXRF, the light element capability of PIXE/PIGE under a helium flux and the spatial resolution of BSEM + EDS was used to characterize chemical composition and corrosion of glass samples (first to fourth centuries ad ) from an important, but scarcely investigated, Roman region of south‐west Iberia (southern Portugal). The geochemical trends and associations of major, minor and trace elements were investigated to shed light on production techniques, the provenance of raw materials and decay mechanisms. The results, while confirming a production technique common to Roman glasses throughout the Empire—that is, a silica‐soda‐lime low‐Mg, low‐K composition, with glass additives as colouring and/or decolouring agents (Fe, Cu, Mn, Sb)—show at one site high Zr–Ti contents, suggesting a more precise dating for these glasses to the second half of the fourth century. The Ti–Fe–Zr–Nb geochemical correlations in the pristine glass indicate the presence of minerals such as ilmenite, zircon, Ti‐rich Fe oxides and columbite in the sands used as raw materials for the glass former: these minerals are typical of granitic‐type source rocks. The unusually high K content in the corrosion layers is consistent with burial conditions in K‐rich soils derived from the alteration of 2:1 clays in K‐bearing rock sequences.     

Tesserae Recycling in the Production of Medieval Blue Window Glass

The purpose of this paper is to develop a means of quantifying glass recycling and to discuss the ‘anachronistic’ chemical composition of medieval blue window glass. This method relies on a new numerical method using kernel density estimates and is based on a database of published glass chemical compositions. It seeks to reveal when, to what extent and why blue tesserae were recycled for the production of French and English blue glass. First, it is suggested that blue glass had an ‘anachronistic’ chemical composition only before the 13th century. Second, the ‘anachronistic’ chemical composition of 12th‐century blue glass comes from the recycling of both blue tesserae and non‐coloured glass. Finally, this recycling was motivated by the scarcity of cobalt sources until mines were found in the 13th century.     

DEEPLY COLOURED AND BLACK GLASS IN THE NORTHERN PROVINCES OF THE ROMAN EMPIRE: DIFFERENCES AND SIMILARITIES IN CHEMICAL COMPOSITION BEFORE AND AFTER ad 150*

In this work we attempt to elucidate the chronological and geographical origin of deeply coloured and black glass dating between 100 bc and ad 300 on the basis of their major and trace element compositions. Samples from the western and eastern parts of the Roman Empire were analysed. Analytical data were obtained by means of a scanning electron microscope – energy‐dispersive system (SEM–EDS, 63 samples analysed) and laser ablation – inductively coupled plasma – mass spectrometry (LA–ICP–MS, 41 samples analysed). Among the glass fragments analysed, dark brown, dark purple and dark green hues could be distinguished. Only among the dark green fragments could a clear compositional distinction be observed between fragments dated to the periods before and after ad 150. In the early samples (first century bc to first century ad ), iron, responsible for the green hue, was introduced by using impure sand containing relatively high amounts of Ti. In contrast, a Ti‐poor source of iron was employed, containing Sb, Co and Pb in trace quantities, in order to obtain the dark green colour in the later glass samples. The analytical results obtained by combining SEM–EDS and LA–ICP–MS are therefore consistent with a differentiation of glassmaking recipes, detectable in glass composition, occurring in the period around ad 150.     

A TECHNOLOGICAL EXAMINATION OF NINTH–TENTH CENTURY AD ABBASID BLUE‐AND‐WHITE WARE FROM IRAQ,AND ITS COMPARISON WITH EIGHTH CENTURY AD CHINESE BLUE‐AND‐WHITE SANCAI WARE*

Eight sherds of ninth–tenth century ad Abbaesid blue‐and‐white glazed earthenware, excavated in 1931 at Hira in western Iraq, were analysed using, variously, quantitative wavelength‐dispersive spectrometry (WDS) and energy‐dispersive spectrometry (EDS) in association with scanning electron microscopes (SEM), and semi‐quantitative X‐ray fluorescence spectrometry (XRF). In order to compare the compositions of the cobalt pigments used, the glazes of seven complete vessels of eighth century ad Chinese Tang blue‐and‐white sancai were also analysed semi‐quantitatively using XRF. The Abbasid wares were shown to have used traditional Mesopotamian alkali–lime glazes applied to calcareous clay bodies. Half the glazes examined were opacified with tin oxide. Three types of blue decoration (i.e., raised; spreading; and flat, non‐spreading) were produced using a variety of formulations, including a mixture of cobalt pigment with lead oxide. The sources of the ores used for the cobalt pigments have not been identified. However, the analytical data showed that the cobalt ore used for the Abbasid blue‐and‐white ware could be distinguished from that used for the Tang blue‐and‐white sancai by its higher iron content and by the presence of a significant amount of zinc. The use of cobalt‐blue decoration on the ninth–tenth century ad Abbasid ware was anticipated in China by eighth century ad Tang blue‐and‐white sancai wares. However, whether its introduction by the Abbasid potters should be seen as an independent invention that followed the introduction of tin‐opacified glazes in Iraq, or whether it was influenced in some way by Chinese originals, is still unresolved.     

Analyses of Early Medieval Stained Window Glass From the Monastery of Baume‐Les‐Messieurs (Jura,France)

The collection of early medieval window glass found in the abbey of Baume‐les‐Messieurs (Jura, France) is exceptional because it dates to the end of the eighth century, and due to the number of fragments as well as their state of conservation. Different colours and forms have been identified. These pieces are a rare opportunity to address the glass craft, its recipes and techniques for a phase of its history that has remained little known. Analyses in PIXE–PIGE prove that, in addition to fragments from two soda glass items, the pieces are made from wood‐ash glass. Most of them probably came from the same production and the raw material is present in the region. At this early stage of wood‐ash glass production, the glassmakers had mastered the glass as well as the colour processes.     

CHARACTERIZATION OF ARCHAEOLOGICAL AND IN SITU SCOTTISH WINDOW GLASS

Scottish window glass from both archaeological sites and historic buildings was examined using portable X‐ray fluorescence (pXRF) and scanning electron microscopy – energy‐dispersive X‐ray micro‐analysis (SEM–EDX). The elemental composition of the glass provides information regarding the materials used and, subsequently, an approximate range of dates of manufacture. pXRF is shown to be more vulnerable than SEM–EDX to the effects of surface corrosion and matrix effects in archaeological samples. The study showed that the production of window glass in Scotland from the 17th century onwards appears to closely parallel that in England. It also demonstrated the potential of pXRF for in situ studies of window glass in historic buildings. pXRF was used to assess two Scottish buildings; one in state care and one in private ownership. The building in state care, the Abbot's House at Arbroath Abbey, showed a uniform glass type, suggesting that the building was re‐glazed completely at some point during the late 19th or early 20th century. The building in private ownership, Traquair House, had a range of glass types and ages, demonstrating a different maintenance and repair regime. This type of data can be useful in understanding historic buildings in the future, particularly if re‐glazing is being considered.     

THE RADIOCARBON CHRONOLOGY OF KOPIA,AN EARLY GLASS MANUFACTURING CENTRE IN INDIA

Right from the time of the Painted Grey Ware (PGW) culture, dating to c. 1200–600 bce , more than 210 archaeological sites in India have provided evidence of glass, but there has been no attempt to date the glass‐yielding layers by radiometric techniques. This has hampered the establishment of a chronology for the beginning and evolution of glass‐making in India. The site of Kopia was excavated by the first author for three seasons from 2004 to 2006 to understand the history, development and technology of glass production in India. The excavation produced evidence of a long period of occupation, covering the Fine Grey Ware (FGW), Northern Black Polished Ware (NBP), Sunga–Kushana and Gupta periods. Twenty accelerator mass spectrometry (AMS) and radiocarbon dates, all derived from charcoal samples and processed independently by three laboratories, are available from the site. The dates range in their calibrated form on average from the ninth to the second century bce in locality I and from the second century bce to the second century ad in locality II.     

Wine Bottles From Lisbon: Archaeometric Studies Of Two Archaeological Sites Dated From The 17th To The 19th Century

Two sets of wine bottles dated between the end of the 17th and the 19th centuries were characterized by means of μ‐PIXE (major and minor elements) and LA–ICP–MS (trace and REE elements). The fragmented wine bottles were recovered from two archaeological contexts in Lisbon and reach a total of 79 fragments. One of the archaeological bottle sets comes from a house structure that collapsed during the major earthquake in 1755, providing a precise terminus ante quem. The second set comes from the exploratory archaeological intervention performed in Rua do Arsenal, where the Côrte‐Real Palace (built in the 16th century), was discovered. From this site, posterior contexts dated up to the 19th century were considered. This systematic study allowed the glass to be identified as high‐lime, low‐alkali (HLLA) for all the considered chronologies. However, the 19th‐century bottles have a different HLLA composition, suggesting the use of synthetic soda. Comparison with data from literature showed some similarity with English, Belgium and French reported compositions. This is the first systematic attempt to characterize the composition of glass wine bottles circulating in Portugal, giving new insights into their probable provenances, and on the exchange between Portugal and its trading allies.     

THE COMPOSITION AND MANUFACTURE OF EARLY MEDIEVAL COLOURED WINDOW GLASS FROM SION (VALAIS,SWITZERLAND)—A ROMAN GLASS‐MAKING TRADITION OR INNOVATIVE CRAFTSMANSHIP?*

Archaeological excavations between 1984 and 2001 at the early Christian cemetery church in Sion, Sous‐le‐Scex (Rhône Valley, Switzerland), brought to light more than 400 pieces of coloured window glass dating from the fifth or sixth centuries ad . The aims of this paper are threefold: first, to characterize the shape, colour and chemical composition of the glass; secondly, to understand whether the production of the coloured window panes followed traditional Roman glazing techniques or was of a more innovative nature; and, thirdly, to provide some indications as to the overall design of these early ornamental glass windows. Forty samples of coloured glass have been analysed by wavelength‐dispersive X‐ray fluorescence. The results of the chemical and the technological studies showed that most of the glass was produced using recycled glass, particularly as a colouring agent. Some of the glass was made of essentially unmodified glass of the Levantine I type. The results taken together seem to confirm that raw glass from this region was widely traded and used between the fourth and seventh centuries ad . The artisans at Sion were apparently still making use of the highly developed techniques of Roman glass production. The colour spectrum, manufacture and design of the windows, however, suggest that they represent early examples of ornamental coloured glass windows.     

COLOUR ATTRIBUTES OF MEDIEVAL WINDOW PANES: ELECTRON PARAMAGNETIC RESONANCE AND PROBE MICROANALYSES ON STAINED GLASS WINDOWS FROM PAVIA CARTHUSIAN MONASTERY*

Stained glass windows from the Carthusian Monastery of Pavia, dating back to the 15th century, were studied by combining two analytical techniques: electron probe micro‐analysis (EPMA) and electron paramagnetic resonance (EPR). Chemical compositions and oxidation states of the transition ions, present as minor elements, were investigated by EPMA and EPR, respectively, in order to ascertain the role played by chromophorous ions in the glass coloration. The investigated glass can be defined as K–Ca glass, and the panes with red, green and blue colours were produced using flashing techniques.     

Glass Beads from 15th–17th Century CE Jar Burial Sites in Cambodia's Cardamom Mountains

A total of 74 glass beads, included as grave goods in 15th–17th century CE jar burials from Cambodia's Cardamom Mountains, were analysed using laser ablation – inductively coupled plasma – mass spectrometry (LA–ICP–MS). Several glass types were identified, including two subtypes of high‐alumina mineral soda glass, and lead–potash glass. The final glass type represents a newly discovered and previously unidentified type of high‐alumina soda glass, with high magnesia (m‐Na–Al Mg>). This study represents the first glass data from the mid‐second millennium CE from Cambodia and sheds light on the multiple long‐distance maritime exchange networks in which the upland people buried in the jars were participating.     

Archaeometric investigation of Roman tesserae from Herculaneum (Italy) by the combined use of complementary micro-destructive analytical techniques

Vitreous tesserae from two mosaics in Herculaneum (Italy) dating from the 1st century AD have been investigated in order to gather information on Imperial Age opaque glass. The combined use of complementary micro-destructive analytical techniques, namely optical microscopy (OM), scanning electron microscopy (SEM) with energy dispersive spectrometry (EDS), inductively coupled plasma-mass spectrometry (ICP-MS), transmission electron microscopy (TEM), and X-ray powder diffraction (XRPD) allowed to define the nature of formers, fluxes, chromophores and opacifying compounds and to determine the type of raw materials employed for their introduction. The results confirmed the high technological level of Imperial Age glassmakers and clarified some details of the production processes. Experimental data have been obtained concerning formation of antimony-based opacifiers. The presence of tin-containing Ca- and Pb-antimonates has been ascertained in various green, yellow and turquoise tesserae. Moreover, unusual divergences from the established Roman age ‘low magnesia–low potash’ (LMLK) glass composition have been found for some red and green samples.