New Data on the Soda Flux Used in the Production of Iznik Glazes and Byzantine Glasses

Previous research has shown that Iznik glazes are characterized by low potash and magnesia contents. It was therefore suggested that the flux used was either a purified plant ash or some unidentified mineral source of soda. More recently, as a result of the detection of small, but significant, amounts of boron and lithium in Byzantine glasses from western Turkey, which also exhibit low potash and magnesia contents, it has been suggested that the source of the flux used was a soda‐rich evaporite associated in some way with the extensive borax deposits in the region. LA–ICP–MS has been used to establish that Iznik glazes also contain similarly small amounts of boron and lithium. The Na/K, Na/Mg, Na/Ca and Na/B ratios for these Iznik glazes are shown to be comparable to the equivalent ratios calculated from published data for waters from a range of Na–HCO₃ type hot springs in western Turkey, with the closest match being to the hot springs around Afyon‐Gazligöl, which is consistent with documentary evidence. It is therefore proposed that the soda‐rich salts produced by evaporating water from these springs to dryness would have provided the flux required for the production of Iznik glazes and high‐boron Byzantine glasses.     

Analytical investigation on Renaissance Venetian enamelled glasses from the Louvre collections

Venetian enamelled glass is one of the most significant subjects of the art and technology of Renaissance glassmaking. These items were made in Venice from the second half of the 15th through the 17th centuries and were imitated in other European glassmaking centers during this period and again in Murano during the 19th century. Only a limited number of analyses of these masterpieces have been published up to now.     

Chemical characterisation and manufacturing technology of late Roman to early Byzantine glass from Beit Ras/Capitolias,Northern Jordan

The finding of considerable collections of glass artefacts, together with considerable lumps of glass chunks, fuel ash slag and kiln fragments related to glass processing strongly suggests a local secondary production (working) of glass at the Beit Ras/Capitolias archaeological site in northern Jordan from the late Roman to the early Byzantine period. The chemical analysis of ancient glasses can provide important information regarding the manufacturing technology of the glass made during a specific period. The aim of this study is to characterise the chemical and technological aspects of late Roman to early Byzantine glasses excavated from this main archaeological site. Furthermore, the present paper aims to provide incontrovertible evidence that this site must be considered as a major centre for the secondary production of glass during a period between the 3rd and the 6th centuries. For this purpose, a considerable group of raw glass chunks and vessel fragments of different colours and typologies were collected. The results of chemical analyses indicated that the glass did not show a clear difference in chemical composition between late Roman and early Byzantine times. All the glasses (artefacts and chunks) are of the soda-lime-silica type and correspond to the previously defined Levantine I glass group. The chemical composition of the glass chunks, identical to that of contemporary glass of the same colour, strongly suggests that these chunks were used for the manufacture of late Roman to early Byzantine glass at Beit Ras. The observation of technological features indicates that glass chunks were produced in massive tank furnaces in other primary production centres elsewhere, and were meant for local reworking. According to the microscopic examination, it can also be observed that mould-blowing was the main technique used for forming glass.     

The glass of Nogara (Verona): a “window” on production technology of mid-Medieval times in Northern Italy

The site of Nogara (province of Verona, Italy) provides valuable insights into the complexities of the glass industry in mid-Medieval times, due to its timing, which ranges mainly between the 10th and 11th centuries AD, and to the great quantity of glass findings, mainly tableware. In the present paper, the combination of archaeological, chemical and textural data allows us to identify production technologies in a time-interval perceived to be a period of technological transition for glass. In particular, the frequent occurrence of recycled natron glass and only a few glass samples made with soda plant ash indicate that recycling of earlier glass was common in inland Northern Italy in the 10th–11th centuries AD. In addition, blue and reticello decorations were obtained by recycling earlier glass mosaic tesserae, as shown by much Co, Cu, Sn, Sb and Pb and the presence of crystallised calcium antimonates. A few glass samples with chemical compositions intermediate between natron and soda plant ash glass were also identified, suggesting a gradual change in glass composition from natron-based towards soda ash-based production technology, which prevailed in the 13th-14th centuries. In conclusion, the difficulty in describing mid-Medieval glass as a well-defined entity, due to the great propensity for recycling earlier glass samples which causes variability in chemical compositions, particularly those of trace elements, is clearly documented here. In any case, this paper contributes to a new type of chrono-typological scanning and to more detailed knowledge of glass production technology during mid-Medieval times in Northern Italy, little found in the literature until now.     

Identifying expedient glass tools from a post-contact Tsimshian village using low power (10–100×) magnification

Glass shards from post-contact contexts at the Northern Tsimshian site of Ginakangeek, on the north coast of British Columbia Canada, are identifiable as expedient tool artifacts through analysis of usewear patterns. In this study, we have examined the nature of glass and argued that its mineralogical properties make it analogous to other lithic materials. Although other researchers have found evidence of a lithic-like industry of glass artifacts based on macroscopic features, we have demonstrated that expedient artifacts are identifiable even in the absence of macroscopic traits, through low-power magnification of usewear. We have also tested this thesis against the possibility that microscopic usewear-like patterns were the product of fragmentation or post-depositional effects, and argued that a suite of usewear traits correlates only with use activity. Our experimental suite of glass artifacts indicates that specific actions (such as cutting, scraping, sawing, and chiseling) and the relative hardness of specific substrates produce particular usewear patterns. A number of potential explanations are considered for the appearance of such an industry on the Northwest Coast more than a century after contact with Europeans.     

The composition of the soda-rich and mixed alkali plant ashes used in the production of glass

Soda-rich plant ashes have been used in the Near East and Egypt in the production of glass and faience from the 4th millennium BC onwards, and mixed alkali plant ashes have been similarly used in western Europe during the 2nd and first half of the 1st millennia BC. In the production of these ashes, the plants of interest are salt resistant, halophytic plants of the Chenopodiaceae family, growing in coastal, salt marsh and desert regions. A primary criterion in selecting ashes for glass and faience production is that the alkalis are predominantly in the form of carbonates, bicarbonates and hydroxides rather than either chlorides or sulphates. In the current paper, previously published data for such ashes are brought together and re-assessed, and new analytical data are presented for ashes produced from plants collected in Egypt, Greece and the UK. For the ashes produced from Salsola kali plants collected from Greece and the UK, the soda to potash ratios (0.3–1.8) do not show any systematic differences between the regions in which the plant was growing, but instead reflect the fact that this species favours the accumulation of K⁺ over Na⁺ ions. Further, the results suggest that S. kali could have been the source of the mixed alkali ashes used in western Europe, if the ashes had first been treated in some way in order to reduce their lime-plus-magnesia contents.     

Trace element discriminants between Egyptian and Mesopotamian Late Bronze Age glasses

The origins of Late Bronze Age glass artefacts found throughout the Mediterranean and Near and Middle East remain controversial. Previous analyses of major and minor elements in both Egyptian and Mesopotamian glasses have proven equivocal, revealing no significant compositional differences between glasses from these two regions. Here we present new Laser ablation-ICPMS analyses of 32 trace elements in 54 samples of both Egyptian and Mesopotamian blue and colourless glasses. Our results show that there are consistent differences between these two suites, which are not related to the colorant and clearly indicate the use of different raw materials and/or manufacturing processes. Compositional variations are related to geological controls, hence this method holds promise for the development of a minimally destructive technique for discriminating between archaeological glasses of different provenance, which will be essential in the interpretation of ancient trade patterns and contacts.     

岭南汉墓出土玻璃珠饰与汉代海上丝绸之路中外交流

汉代海上丝绸之路,通过海路沟通了我国岭南与东南亚、南亚,以及地中海沿岸等地区。岭南地区作为汉代海上丝绸之路始发港所在地,对于研究汉代中西交流具有重要意义。玻璃珠饰是岭南汉墓出土器物中最为典型的一类。本工作对岭南汉墓出土玻璃珠饰的玻璃成分体系和制作工艺进行了总结,并基于化学成分和器型风格,对玻璃珠饰的产地来源进行了探讨,进一步阐明了汉代岭南地区与东南亚、南亚以及地中海沿岸等地区之间的交流。岭南汉墓出土玻璃珠饰为汉代海上丝绸之路中西交流提供了确凿可信的实物证据,对研究汉代中外交流具有重要的学术价值和研究意义。     

Glass beads and pendants from Meroitic and Nobadian Lower Nubia,Sudan: Chemical compositional analysis using laser ablation‐inductively coupled plasma‐mass spectrometry

This paper presents a detailed elemental analysis of 64 glass beads and pendants dated to the Meroitic period (first–third centuries ad ) and the Nobadian period (fourth–sixth centuries) from burial sites in the Lower Nubian Nile Valley region. Laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) was used to determine the chemical composition of the glass and to gain knowledge about its origin. Four main glass types were identified: low‐alumina soda‐lime glass, high‐alumina glass, plant‐ash soda‐lime glass, and mixed‐alkali glass. Mineral soda‐lime glass (m‐Na‐Ca) of East Mediterranean/Egyptian provenance is dominant within the low‐alumina glass group from Meroitic and Nobadian periods. Mineral soda high‐alumina glass (m‐Na‐Al) appeared in the Nobadian bead assemblages, and the m‐Na‐Al 1 subtype was produced in Sri Lanka/South India. An initial insight into the origin of the glass beads in Nubia from the first to sixth centuries is described, indicating the first evidence for the presence of Asian objects in Nubia. The data obtained for the bead trade in North‐east Africa in this study has allowed a new light to be shed on the westward flow of Asian glass during a time of intensive maritime trade contacts with the wider Indian Ocean world.     

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.