Pre-Roman glass from Mozia (Sicily-Italy): the first archaeometrical data

This study present the results of an archaeometrical investigation performed on a series of opaque pre-Roman glass (vessels and ornaments) dated from the 6th to 4th century BC coming from Sicily. Sixteen core formed vessels, twelve beads, three pendants and one spindle-whorl recovered in the Phoenician-Punic sites of Mozia and Birgi were analysed thought a micro destructive approach. The complete chemical analyses and X-Ray diffraction analyses were performed on small fragments of glass. The aims of this work are: 1) to obtain a chemical characterization of these samples in order to understand the raw materials employed for their production; 2) to obtain information regarding the opacifying phases dispersed in the glass; 3) to make a comparison with the results recently obtained on coeval and similar finds recovered in other cultural context, in particular in Northern Italian Etruscan contexts in order to understand whether they could belong to the same Greek-Eastern production.     

Byzantine glass mosaic tesserae: some material considerations

Abstract

Issues about the manufacture of Byzantine mosaics and the implications of these in wider terms relating to social and economic questions about the art form have been little discussed. This paper brings together evidence about Byzantine glass mosaic tesserae gathered from archaeology, glass technology and glass analysis, and synthesizes these into a discussion of three aspects: distribution; manufacture; trade and price. It looks to examine how these different elements can be used to form a more detailed composite picture about the production and distribution of Byzantine mosaics. It also proposes ways in which glass analysis can be used in a more coherent way to extend our understanding of mosaic glass production.     

Chemical characterisation of glass mosaic tesserae from sixth-century Sagalassos (south-west Turkey): chronology and production techniques

Little is known about the origin, supply pattern and production technology of Byzantine glass mosaic tesserae. In this study, we have analysed forty-eight glass tesserae from Sagalassos (Asia Minor) of different colours and from two archaeological contexts that were stratigraphically dated to the sixth century CE. The main aim was to identify the raw materials, colourants and opacifiers as well as secondary working practices that are reflected in the composition (EPMA, LA-ICP-MS analyses) and the microstructure (XRD, SEM-BSE) of the tesserae. The set of samples retrieved from the Roman Baths complex at Sagalassos is compositionally very homogeneous, representing possibly a single commission, and can be tentatively dated to the late Roman period. In contrast, the assemblage associated with the construction of a Byzantine church around the turn of the sixth century CE is more diverse, suggesting that these tesserae were produced from more than one silica source. This highlights a diversification in the supply and manufacture of glass tesserae during the Byzantine period.     

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.     

The palaeo-Christian glass mosaic of St. Prosdocimus (Padova,Italy): archaeometric characterisation of tesserae with antimony- or phosphorus-based opacifiers

The present paper reports the results of archaeometric characterisation of the opaque tesserae, intentionally coloured with antimony- or phosphorus-based opacifiers, coming from one of the two only palaeo-Christian glass mosaics known in the Veneto region (Italy), i.e., the mosaic which decorated the votive chapel of St. Prosdocimus in Padova. In particular, 55 tesserae belonging to glass types “White”, “Blue”, “Yellow”, “Green” and “Brown” are examined here. The multi-methodological approach (SEM-EDS, EMPA, XRPD, imaging spectroscopy coupled, in some cases, with XAS) gave valuable insights into the complexities of palaeo-Christian glass mosaic production technologies. Two main groups are identified, one characterised by glassy matrixes and opacifiers (calcium or lead antimonate) typical of the Roman period and comprising all “White”, “Blue”, and “Yellow” tesserae and some “Green” ones, and the other characterised by glassy matrixes and an opacifier (calcium phosphate) typical of the 6th century AD, composed of “Green” and “Brown” tesserae. This suggests that, during that century there was a gradual change from older to “new” production technologies: although new opacifiers such as calcium phosphate started to be used, the frequent use of antimony-based ones (43/55 samples) supports the hypothesis that their systematic use was extended until the 6th century, although re-using old tesserae cannot be completely excluded. In addition, comparisons with compositional groups already identified in the “gold” tesserae of the same mosaic and tesserae from Ravenna demonstrate that both the same “base compositions” of the glass were used to produce transparent and opaque glass. This evidence, coupled with the results of the historical-artistic study, suggests technological connections between Padova and Ravenna, the capital of Byzantine mosaics in Italy. Micro-structural observations and chemical analyses of the Paduan antimony-based opacified glass demonstrate that different processes and raw materials were used in their production. Both in situ and ex situ crystallisation can be identified for calcium and lead antimonate in Paduan tesserae, whereas the production of tesserae opacified with calcium phosphate generally appears to be highly standardised. Although the opacifiers used in the Paduan tesserae support technological transitions, the colouring elements identified here, i.e., iron and manganese for white, yellow, brown and some green tesserae, cobalt for blue, and copper for blue and green, suggest continuity, because their use is widely testified in the production of both transparent and opaque glass artefacts dating from the Bronze Age until Medieval times, from whichever archaeological site the samples come. Peculiar relationships among the oxidation states of colouring elements, their contents in the glassy matrix, the types of opacifiers used, and the final colour of tesserae were identified. In addition, the correlations of cobalt and/or copper with other elements, together with identification of relics of colouring and “metallic” droplets, allow us to speculate on possible sources and production technologies. Lastly, identification of newly formed crystalline inclusions in tesserae also yields information on kiln temperatures, which ranged between 900 and 1150 °C, a range easily reached in the furnaces of the 6th century AD.     

The first archaeometric data on polychrome Iron Age glass from sites located in northern Italy

A large sample set of transparent and opaque glass artefacts recovered from Etruscan contexts in northern Italy (Bologna and Spina (FE) necropoleis) and dated to a period between the 6th and 4th century BC are analysed in this paper. Samples of highly decorated beads, spindle whorls and vessels of the ‘Mediterranean Group I’ (Alabastron, Oinochoes, Amphoriskos) were selected in order to determine whether these different glass artefacts were produced at the same manufacturing site. While the vessels almost certainly originate from Greece, the beads could derive from a more ancient local production ascertained at the site of Frattesina (Rovigo, Italy) and dated to the Bronze Age.     

Glass and metal analyses of gold leaf tesserae from 1st to 9th century mosaics. A contribution to technological and chronological knowledge

An archaeometric study was carried out on 40 gold leaf tesserae from mosaics in Italy dated 1st to the 9th century AD. Glass layers and gold leaf were both analysed by X-ray microanalysis. The main aim was the identification of the composition of the glass and of the gold leaf, in order to assess the variations in composition and nature of the tesserae in the examined period.     

The Mediterranean Group II: analyses of vessels from Etruscan contexts in northern Italy

A large number of Mediterranean Group vessels were recovered at the Etruscan site of Spina in northern Italy and dated from the 6th to the 3rd century BC. In this work a number of vessels belonging to the so-called “Group II” were analysed. The samples are mainly Alabastra, Oinochoai, Amphoriskoi, and Hydriai, in general opaque and deeply coloured. The aims of this study are: 1) to characterize these samples since there is a lack of data in literature regarding Mediterranean Group II; and 2) to compare the data obtained with that of glass for previous centuries (Mediterranean Group I) recovered at the same site in order to establish whether they could have the same origin. The chemical analyses of major and minor elements were carried out by electron microprobe and the nature of the opacifying and colouring agents was determined by X-ray diffraction. The sample set is relatively homogeneous and most of the samples can be classified as Low Magnesium Glass produced with natron and a calcareous silicatic sand. The XRD analyses proved the use of lead antimonates in the manufacture of yellow decorations and of calcium antimonates in the white and light blue decorations. The consistency of the chemical compositions of Mediterranean Groups I and II samples makes it possible to hypothesize a common origin.     

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.     

New insights into Byzantine glass technology from loose mosaic tesserae from Hierapolis (Turkey): PIXE/PIGE and EPMA analyses

This study focuses on the Byzantine glass tesserae from Hierapolis (Phrygia, central Turkey). Fifty-seven samples of loose tesserae from two sites in the town (the theatre and the church of St. Philip) are analysed by particule-induced X-ray emission and particule-induced gamma ray emission and electron probe X-ray microanalysis to obtain the chemical composition and identify the colourants and opacifiers. The aims are to add new information to the scant knowledge of the Byzantine glassmaking technology, to constrain the chronology of the mosaics and to trace the supply routes of the tesserae. In the destruction layers of the theatre, tesserae produced following the Roman glassmaking technology (natron glass opacified by calcium and lead antimonate) were found. They were made using a Levantine 1 raw glass, generally attributed to the early Byzantine period (fifth to sixth c.). In the church, the samples attest a technological change from Roman tradition, and a complex pattern according to building history (two phases are attested, probably in the sixth and eighth to ninth c.), and a multiplicity of supply. Three glass types and some recipes not attested before in this chronological range for the production of tesserae are documented, such as the use of a local low-chlorine natron glass for the production of black and red tesserae, the blue colouring by a source of cobalt with zinc in a natron glass tessera and the opacification with tin oxide (both in a lead-free and in a high-lead natron glass), as well as with quartz.     

Southern African glass beads: chemistry,glass sources and patterns of trade

Three-hundred-and-sixty glass beads from 19 archaeological sites in southern Africa dating between about the 8th and 16th centuries AD were analyzed using LA-ICP-MS, determining 47 chemical elements. The eight different bead series, previously defined on morphological characteristics, possess different glass chemistries. Some bead series were made from plant-ash glasses, others from soda-alumina glasses. Zhizo series beads of the late 1st millennium AD were probably made from Iranian glass. Later bead series were made of glass probably manufactured in South Asia, though there are changes through time in both South Asian glass recipes and bead morphologies.     

新疆宋元时期也木勒遗址出土玻璃的工艺与成分研究

也木勒遗址位于新疆维吾尔自治区塔城地区额敏县,是北方丝绸之路上的重镇,考古发掘确定其为宋元时期的大型遗址。为探讨该遗址出土玻璃的成型工艺和来源,本研究以该遗址中的9个玻璃碎片作为对象,通过观察成型工艺,并利用激光剥蚀电感耦合等离子体原子发射光谱(LA-ICP-AES)技术分析样品的化学成分。结果显示,这批素面透明的玻璃片为无模吹制而成的日常实用器皿,成分上属于钠钙玻璃体系,Na_2O含量低,K_2O含量较高,并含有P_2O_5,助熔剂可能是含有草木灰的混合碱,成分特征与同时期葱岭以西中亚地区、新疆地区生产的玻璃器相似。结合新疆同时期玻璃器发现,多是装饰简洁,出土地点等级一般的普通实用性器皿,说明玻璃器已进入平民的日常生活之中,反映出新疆地方民族政权较中原地区先融合了中西亚将玻璃器作为日常生活用具的文化,形成了与中原玻璃器功用的差异之处。研究结果为丰富国内宋元时期新疆玻璃器的研究资料,揭示新疆地区玻璃器的使用面貌,探讨宋元时期少数民族地方政权的文化交流提供重要信息。     

A non-invasive study of Roman Age mosaic glass tesserae by means of Raman spectroscopy

Ancient mosaic tesserae are a range of materials of very varied and complex nature, including pottery, stone and glass. Raman spectroscopy is a powerful tool for the analysis of all these kinds of materials. In the particular case of glasses, this technique can be used both for a study of surface weathering and for the characterization of bulk structure, but it has not yet been extensively used for the characterization of mosaic glass tesserae. We carried out Raman analyses on a set of Roman and Late Antiquity period mosaic glass samples, which allowed a good characterization of both the glass matrix and the crystalline inclusions. All the samples show the typical Raman signatures of soda-lime-silicate glasses. Several crystalline phases were also identified, being relics of raw materials used during the glass manufacturing process, such as quartz and feldspars, or linked to the glass color/opacification, such as bindheimite and cuprite. The analyses also led to the identification in some blue, turquoise and green tesserae of calcium antimonate, whose Raman signature has only recently been recognized in the scientific literature on mosaic glasses. Some emphasis is given to the analysis of red lead-containing tesserae, colored with Cu⁺ ions or even Cu⁰ (or Au⁰) metal nanoparticles. Samples with peculiar compositions, as well as “modern” (and restoration) samples, could quite easily be distinguished from the ancient ones by their Raman spectra.     

The mosaic of the crypt of St. Nicholas in Bari (Italy): integrated GPR and laboratory diagnostic study

The crypt of St. Nicholas in Bari, Southern Italy, is a building of cultural worldwide importance. Inside the crypt a mosaic develops on the apsidal floor and along a parietal seat placed along the apsidal masonry, in the form of cladding. A surviving portion of the mosaic pavement is also preserved in the right lateral chapel. Integrated non-destructive survey and laboratory analyses were undertaken for the diagnostic study of the mosaic. GPR prospection was successfully applied to the study of its conservation state, that is strictly related to the condition of the subsoil, in particular to the presence and distribution of water. The presence of water, whose rise interests also some portions of the masonry and water content distribution were identified by the results of electromagnetic wave velocity analysis in GPR data.     

Mineral soda alumina glass: occurence and meaning

Mineral soda–alumina (m-Na–Al) glass has been found across a vast area stretching from Africa to East Asia. m-Na–Al glass appears around the 5th c. B.C. and is relatively common for periods as late as the 19th c. A.D. It is particularly abundant in South Asia, where raw materials to produce m-Na–Al glass are readily available, and was likely manufactured there; however, the number and the importance of the manufacturing centers is unknown as archaeological information are extremely scarce. The interpretation of data obtained using compositional analysis on a large corpus of artifacts (486) shows that at least five sub-groups of m-Na–Al glass can be identified using the concentrations of calcium, magnesium, uranium, barium, strontium, zirconium and cesium measured with laser ablation – inductively coupled plasma – mass spectrometry (LA-ICP-MS). From this data, it is possible to infer the existence of several m-Na-Al glass making centers, not all of them located in South Asia as previously assumed. They were operating over different time periods and were connected to different exchange networks.     

Late antique glass from Salapia: Tracking production and trading networks

The investigation of 38 late antique vessels from the archaeological excavation of Salapia has been performed using EMPA and LA-ICP-MS. The collection was made using impure sands and mineral soda. Among coloured glass, most vessels were made of ‘fresh’ glass. The use of colouring agents is rare, and most decoloured glass is obtained by Mn addition. Sb-decolouration is limited to one cup, and two colourless vessels show both manganese and antimony. As for provenance, the prevalence of Egyptian-HIMT glass over the Levantine is evident. Among Levantine glass, Jalame glass is represented, whereas Apollonia glass is absent. Among Egyptian (and deemed Egyptian) glass, the prevalence of HIMT glass over the other types has been observed. The high attestation of fresh glass, most notable in the earlier centuries, suggests the importation of glass in the form of finished objects, especially luxury vessels.     

益门二号墓出土红色粉末的化学与矿物学性质

为了解宝鸡益门二号墓出土的红色粉末的化学组成及作用,使用X射线衍射仪和扫描电子显微镜(SEM)以其配备的能谱仪(EDS),对它们进行了分析研究。结果表明,此红色粉末为纯朱砂。它对墓藏中的尸体和棺木有防虫防腐的作用。     

Innovation and tradition in the fourth century mosaic of the <Emphasis Type="Italic">Casa delle Bestie Ferite</Emphasis> in Aquileia,Italy: archaeometric characterisation of the glass tesserae

The present paper focuses on the archaeometric characterisation of 38 glass tesserae of various colours from an in situ mosaic in Aquileia, Italy, dated to the second half of the fourth century AD. The examination of the textural, mineralogical and chemical features, conducted by means of a multi-methodological approach (optical microscopy (OM), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), electron probe micro analysis (EPMA), X-ray diffraction (XRD) and Fibre Optic Reflectance Spectrophotometer (FORS)), has provided valuable insights into the changes in the production technology during the transition between the Roman and the Late Antique periods. The assemblage is heterogeneous, and each chromatic group is composed of tesserae produced with different base glasses and colouring/opacifying techniques, suggesting diverse supplies. A small group of tesserae shows strict links to the Roman tradition in terms of both base glass and colouring/opacifying techniques and was probably obtained by re-using tesserae from older mosaics. Conversely, a larger group of tesserae shows textural and chemical evidence of recycling and indicates the prompt use of “new” opacifying technologies (such as the use of tin compounds) or uncommon technological solutions (such as the use of quartz and bubbles as opacifiers or the addition of metallurgical slags in red tesserae), suggesting a specific production in the fourth century AD.     

Analyses of colourless Roman glass from Binchester,County Durham

Forty samples of Roman colourless glass tableware from Binchester, dating from the 1st to mid-3rd centuries AD, were analysed using ICP spectrometry and parallels were sought with similar studies of Roman glass from Colchester and Lincoln [C. Mortimer, M.J. Baxter, Analysis of Samples of Colourless Roman Vessel Glass from Lincoln, Ancient Monuments Laboratory Report 44/1996, 1996; H.E.M. Cool, J. Price, Roman vessel glass from excavations in Colchester, 1971–1985, Colchester Archaeological Report 8, Colchester Archaeological Trust Ltd. and English Heritage, Colchester, 1995; M.P. Heyworth, M.J. Baxter, H. Cool, Compositional Analysis of Roman Glass from Colchester Essex, Ancient Monuments Laboratory Report 53/1990, 1990]. Some samples from the Binchester, Colchester and Lincoln (BCL) groups were re-analysed using energy dispersive spectrometry (SEM–EDS) and the results were used to compensate for the differences in reproducibility between the ICP data sets, so that these could be directly compared. The majority of the glass from all three sites was similar but some distinct compositional characteristics were identified that were specific to certain types of ware. There were differences in the concentration of lead in the samples, which appear to be to some extent chronological. The compositional data for the glass from Binchester, Colchester and Lincoln were also compared to literature data for various types of natron glass produced in the 1st millennium AD.