Search Results (23)

Museums may acquire archaeological artefacts discovered by non-specialists or amateur archaeologists, holding the potential to promote the safeguarding of cultural heritage by integrating the local community in their activities. However, this also creates an opportunity for the fraudulent sale of modern forgeries presented as archaeological artefacts, resulting in the need for a critical assessment of the artefact’s authenticity prior to acquisition by the museum. In 2019, the regional museum in Cáceres (Spain) was offered the opportunity to acquire a Phoenician-Punic head pendant, allegedly discovered in the vicinity of the city. The artefact’s authenticity was assessed by traditional approaches, including typological analysis and analysis of manufacture technique, which raised doubts about its purported age. VP-SEM-EDS analysis of the chemical composition of the different glass portions comprising the pendant was used for non-invasive determination of glassmaking recipes, enabling the identification of glass components incompatible with known Iron Age glassmaking recipes from the Mediterranean. Further comparison with historical and modern glassmaking recipes allowed for the identification of the artefact as a recent forgery made from glasses employing modern colouring and opacifying techniques. Full article

Recent archaeological sites dating to the late 19th and early 20th centuries have rarely been studied to date. Among the 500 “glassy” beads excavated from Dohouan (Côte d’Ivoire), elemental analyses reveal that fewer than half contain abnormally high alumina contents, associated with a soda–potash–lime flux (three compositional groups). The remaining beads are typical lead-based glass. The Raman spectra of the alumina-rich beads are quite complex due to their glass–ceramic nature, combining features similar to the vitreous phase of porcelain glaze with the presence of various crystalline phases (quartz, wollastonite, calcium phosphate, calcite). Organic residues are also observed. Colors are primarily produced by transition metal ions, although some specific pigments have also been identified. These characteristics suggest that the alumina-rich beads were manufactured by pressing followed by sintering, as described in patents by Richard Prosser (1840, UK) and Jean Félix Bapterosse (1844, France). A comparison is made with beads from scrap piles at the site of the former Bapterosse factory in Briare, France. This process represents one of the earliest examples of replacing traditional glassmaking with a ceramic process to enhance productivity and reduce costs. Full article

A series (n = 22) of glasses from the site Kapucinski vrt (garden of the Capuchin monastery, 5th–17th c. CE) in Koper (Capodistria), a port town in the northern Adriatic, was measured using a combined PIXE and PIGE method. Koper has been continuously populated since the late Roman period, with a rich medieval history, thus offering an opportunity to study Early Medieval glass. Stemmed goblet fragments, in the original publication dated between the 6th–9th centuries CE, and several other vessel types (beakers and flasks or bottles and lamps) were selected for analysis. The measurements were expected to show the trends in glass production and consumption from Late Antiquity until the Middle Ages, notably the transition between natron to plant ash glass and the supply of fresh glass. Among the set of 22 glass vessel fragments, both natron and plant ash glass were identified. For finer classification, we relied on a newly developed method of Euclidean distances with respect to major concentrations. Natron glass of the types Foy 2.1 (9 examples), Magby (2 examples), and Levantine I (Apollonia; 2 examples) was found. Two glasses remain undetermined but testify to an Egyptian origin. Most natron glasses show signs of recycling. Among the three unrecycled glasses (about 20% of the whole set), there are two examples of Levantine glass and a Magby glass lamp; this may indicate a modest supply of fresh glass during the period. Plant ash glass may be attributed to the Early or High Middle Ages, exploiting the purified alkalis of the Levantine coasts (known as alume catino in later Venetian glassmaking), and the admixture of impurities in the siliceous sands suggests the circulation and consumption of glass that was produced and traded in the eastern Mediterranean since the 10th century CE. Full article

Amber glass has been produced since at least the 6th century BC. Its value derives from its ability to mimic natural amber and, later, from its ultraviolet filtering properties. Until the 19th century, amber glass was widely used for the storage of food and medicines because its protective properties had been empirically recognized. This study investigates historical methods of amber glass production by using glass recipes from four Portuguese arcana (1793–1975) and focusing on Fe-S and Fe-Mn chromophores. Five recipes were reproduced under controlled laboratory conditions, resulting in 21 experiments. Of these, only 10 produced amber glasses were with different shades. Chemical compositions were analysed by WDXRF, while DSC and dilatometry were used to assess thermal properties. Vickers hardness tests and UV–visible absorption spectroscopy provided insight into mechanical strength and chromophore presence. The study found that FeS amber glass was more difficult to produce than Fe-Mn amber glass, given the complex variables involved in the former, such as SO₃ volatility affecting the final product. Reproduction of historical recipes showed that, even without modern chemical knowledge, historical glassmakers developed practical, empirical methods for making amber glass. These findings contribute to a broader understanding of glass conservation and highlight the importance of historical glass recipes for the interpretation and conservation of glass objects. Full article

Recent research conducted by Heritage Crafts, a prominent national advocacy organisation dedicated to preserving traditional heritage crafts in the UK, has unveiled a concerning trend: several traditional craft skills teeter on the edge of extinction within the UK. This revelation stems from the Heritage Crafts Red List of Endangered Crafts, an initiative which identifies crafts facing the risk of endangerment. In their recent 2023 publication, Heritage Crafts highlighted the distressing decline of cut and engraved glass craftsmanship in the UK, categorising and placing both brilliant cutting (as endangered) and copper wheel engraving (as critically endangered) on the Red List of Endangered Crafts in the UK. This means that these crafts pose the risk of not being actively practised. In December 2023, the alarming downturn of these crafts in the UK was explored and discussed during a conference held at Edinburgh College of Art (ECA), entitled Edo-Kiriko: The Art of Japanese Cut Crystal. This event explored the cross-cultural connection and exchange that exists between Scotland and Japan, drawing upon a rich historical exchange that saw the transmission of Western-style glassmaking from Scotland to Japan in the 1870s–1880s. It also details the more recent exchange that has been in place between Edinburgh College of Art (ECA) and the Horiguchi Kiriko glass studio in Tokyo, Japan. This modern-day exchange has seen the recent transmission of glass-cutting skills through a masterclass led by Toru Horiguchi at ECA. This paper presents this conference, introducing the invited speakers and creating a commentary on the proceedings and the plenary discussions that unfolded. Focus and discussion will be given to the factors that have contributed to the current decline of cut and engraved glassmaking in the UK and the possible measures that could be taken to support and safeguard this field. The final part of this paper will offer a reflection on the conference proceedings and will conclude by making an urgent call for the future of cut and engraved glass craftsmanship in the UK. It is hoped this paper will draw attention to the urgent need for support from education and funding bodies, to safeguard and protect these vital heritage crafts, which boast a rich history in the UK. Full article

Labradorite is a beautiful and popular mineral known for its iridescent play of colour. It is commonly found in igneous rocks and belongs to the feldspar group of minerals which are common in sulfidic Cu-Ni-PGM ores in South Africa. Labradorite primarily consists of calcium, sodium, aluminum, and silicon. There are various uses for labradorite, these range from its use as an ornamental stone to being an additive in ceramics and in glassmaking. Therefore understanding its behaviour under various water conditions is therefore important not only for froth flotation where process water of high ionic strength is used but also important for the question of how ceramics with labradorite as an additive would be affected when subjected to water of high ionic strength and water containing Ca²⁺, Mg²⁺, Cl⁻ and SO₄²⁻ ions in significant quantities. This study therefore examined the behaviour of labradorite in changing water quality, specifically of increasing ionic strength. Labradorite particles were investigated for their behaviour under varying ionic strength of water using two techniques, namely the zeta potential analyser and UV-vis spectroscopy in order to understand the impact of water quality on surface chemistry of labradorite. The zeta potential analyser was used to understand effects on the surface charge of the mineral whilst UV-vis spectroscopy was used to determine the adsorption of sodium carboxymethyl cellulose (CMC) at the mineral surface. CMC was important in this study not only because of its use in flotation as a depressant but also due to its role in materials manufacturing as a binder and rheology modifier, both of which are significant properties in the production of ceramics and pellets. The results of this study showed that the adsorption of CMC, is enhanced in water of high ionic strength. It was also shown that the electrokinetic potential of labradorite increased and became less nagative in water of higher ionic strength, thus demonstrating a passivation effect at the labradorite mineral surface. The findings of this study imply that gangue minerals associated with or of a similar nature to labradorite, such as the feldspar group of minerals in sulfide ore flotation, are likely to be depressed in flotation. Furthermore, the results from this study may be valuable for the ceramics and glassmaking industries, where labradorite is used as an additive, especially in cases where their products are exposed to harsh water conditions. Full article

Lost-wax glass casting, an esteemed yet technically demanding art form, traditionally relies on specialized, costly kiln equipment, presenting significant barriers to artists regarding equipment affordability, energy efficiency, and the technical mastery required for temperature control. Therefore, this study introduces an innovative approach by integrating a microwave kiln with standard household microwave ovens, thus facilitating the lost-wax glass casting process. This methodological adaptation allows artists to employ readily available home appliances for glass creation, significantly reducing the process’s cost and complexity. Our experimental investigations reveal that, by using a 500W household microwave oven for heating, the silicon carbide (SiC) in microwave kilns can efficiently absorb microwave energy, allowing the kilns to reach temperatures exceeding 700 °C, a critical threshold for casting glass softening. We further demonstrate that by adjusting the number of heating cycles, producing high-quality, three-dimensional(3D) glass artworks is feasible, even for large-scale projects. In addition, the microwave kiln can be used as an effective cooling tool to uniformly cool the formed casting glass. This study presents a possible alternative to conventional kiln technology and marks a paradigm shift in glassmaking, offering a more accessible and sustainable avenue for artists and practitioners. Full article

Phoenician colonisation of the Iberian Peninsula in the 1st millennium BCE introduced many novel and luxurious goods to the local populations of the Western Mediterranean. Among them, black-appearing glass beads are characteristic of indigenous female burials in Southern Portugal during the 6th century BCE. This study presents the results of the first comprehensive archaeometric investigation of black-appearing glass from Vinha das Caliças 4 (Portugal), and of black-appearing glass from the Iberian Peninsula in general. A multi-analytical approach employing Stereomicroscopic observation of manufacture and use traces, VP-SEM-EDS, μ-XRD, and LA-ICP-MS was used to cover a wide range of questions regarding technology and provenance. All analysed samples are natron glass. All samples of black and white beads are characterized by high Zr and low Sr values typically ascribed to the use of Egyptian sands. A comparison of the results of previous studies from the same site clearly demonstrates at least two geochemical provenances for Phoenician-traded glass beads, located in the Levantine region and Egypt, respectively. Furthermore, different colours of glass in individual polychrome beads exhibit similar trace element patterns, which might suggest these beads could have been produced close to glassmaking sites/regions. Full article

Glass is made from sand—a finite resource. Hence, there is a need to maintain glass in the industrial cycle as described in the Ellen MacArthur Foundation’s circular-economy diagram. This research project examines the reallocation of material resources in the form of waste glass fines from the industrial recycling process for soda-lime glass. According to the plant manager of Reiling Glasrecycling Danmark ApS, the fines are currently sold to be used for insulation. Although this process prolongs the lifespan of the fines before they become landfill waste, a closed-loop circular option would be preferable. In order to establish a closed-loop circular model for waste glass fines, this research investigates their material and aesthetic qualities and proposes a strategy for maintaining the fines in the closed loop cycle together with the soda-lime glass. The fines are manipulated through robotic deposition and formed into 3D geometries. To expand the aesthetic applications for the material, an investigation is conducted by combining 3D geometries with the traditional glassmaking techniques of glassblowing and casting. The research contributes knowledge of the materials’ technical qualities including printability, durability and workability of the 3D prints combined with cast or blown recycled container glass as well as with blown waste glass fines. Technical obstacles are revealed and alternative routes for further explorations are suggested. Finally, the performative and aesthetic qualities of the results are discussed, while artistic applications for recycled soda-lime glass fines remain to be explored in future research. Full article

Ancient glass has been extensively studied from a technological and raw material provenance perspective since the middle of the 20th century. With the rising applications of analytical techniques in the field of Heritage Studies, the last two decades saw an exponential increase in publications on ancient and historical glass technology from around the globe. Given the amount of works on glass chemical composition, it is surprising to note that the long-held production model for Iron Age glasses found in Europe has only recently been challenged by the publication of uncharacteristic glass compositions. Traditionally, LBA glass industries based on plant-ash fluxes/HMG (Egypt and the Levant) and mixed-alkali fluxes/LMHK (Italy) are thought to be supplanted by natron-fluxed/LMG production operating in Egypt and the Levant since around the 9th century BCE. Recently, however, arguments have been put forth for a more diversified network of glassmaking traditions, including small-scale autonomous European workshops. This article reviews the current state of research into Iron Age (1st millennium BCE) glasses in Europe by examining the available published data on glass compositions to critically assess some practical and theoretical issues stemming from this heterogenous field of research. Key questions are addressed, and future lanes of research are proposed. Full article

Roman glass is well studied and known to have been produced from a mineral soda source and calcareous sand with variation between elements relating to naturally occurring minerals in the sands. While the common characteristics of colourants and opacifiers used in opaque and translucent glasses are well understood, the diverse elemental composition of colouring agents associated with the highly specialised, and largely unexplored, technique of enamel-painted glass has never been firmly established. There remains a significant gap in knowledge of pigments used for this technological innovation which is here addressed through the deployment of non-invasive portable X-ray Flourescence (pXRF) analysis and microphotography on a unique Roman enamel-painted gladiator glass from Vindolanda fort. This vanguard research has successfully established, for the first time, a palette of pigments associated with this specialist technique. It is now possible to unravel previously unknown information on complex manufacturing processes and significantly expand the repertoire of the pigments bound up in enamelling recipes used to depict the striking iconographic scenes on the Vindolanda vessel and, potentially, other Roman enamelled glassware. The detection of Cinnabar, Egyptian blue, Orpiment and other pigments are ground-breaking discoveries that will have a transformative impact on early glassmaking studies and push the boundaries of scholarship into new directions of analytical approaches in heritage materials science to complement recent success in this field with Raman spectroscopy and other techniques. The methodology is unprecedented and has been validated through the high quality of the resulting data which permits the extrapolation of elemental compositions of enamelling materials from those associated with the base vessel. This unique approach provides remarkable insights that will revolutionise our understanding of enamelling technologies using the Vindolanda vessel as the investigative platform for forgotten practice. Full article

In industrial applications such as chemical plants, cement factories, and glassmakers, large-sized centrifugal fans are commonly used for dust-laden flow processing. In many cases, the contamination is due to solid particles responsible for fouling and erosion issues. Erosion induces the reduction of mechanical resistance and, at the same time, the modification of the geometry and the surface characteristics of the internal flow path. The process works according to the characteristics of the erodent particles, such as dimension and hardness, which have to be coupled with the mechanical properties of the substrate, like hardness and roughness level. In addition to this, the intensity of the erosion depends on the dynamic characteristics of particles, especially velocity and impact angle. For these reasons, erosion-related issues are difficult predict and reduce. In an attempt to preserve the structural integrity of the internal walls, wear-resistant plates are positioned where the impacting contaminants are supposed to be more detrimental. In the present work, a combined experimental and numerical approach is proposed to evaluate the proper setup of wear-resistance plates over the flow path of a large-sized centrifugal fan. The results show how different regions (rotating and stationary walls) are subjected to different impact behavior, determining that the design of the position of the wear-resistant plate is not straightforward. Suggestions related to reducing the erosion intensity are reported, highlighting the possibility of designing the best compromise between erosion, performance, and costs. Full article

Three major corpora of architectural glazed bricks from Ancient Mesopotamia dating to the Neo-Assyrian (Aššur and Khorsabad sites) and the Neo-Babylonian (Babylon site) Periods have been submitted to an in-depth comparative study of the orange–yellow and black glazes. Distinct hues in the orange–yellow range were observed according to the archaeological site. They appear to have been well mastered by the glassmakers, consisting in the ex situ preparation of the antique lead antimonate pigment and its mixing with transparent soda-lime glass frit or with the glass-forming components. The intentional addition of hematite or of Cu²⁺ colouring ions in a controlled amount is suggested in two cases. SEM-EDX and Raman analysis of the lead antimonate pigments have pointed out different chemical substitutions in their pyrochlore structure, mainly Fe³⁺ in the Sb⁵⁺ site and Ca²⁺ in the Pb²⁺ site, the proportion of which being correlated to the pigment shade (from pale yellow to orange–red). Part of these substitutions arises from the chemical reaction of the pigment with the hematite and glass melt during firing. Regarding the black glazes, an unexpected colouring technique involving copper sulphide nanoparticles together with the chromophore Fe³⁺-S²⁻ is highlighted for Khorsabad (8th century BC) and for Babylon (6th century BC). For Aššur blacks, the study reveals a change in their colouring technique between the 9th and 8th centuries BC, from a colouration with Mn oxides to an enigmatic one that could also have involved copper sulphide nanoparticles. Full article

Portuguese archaeological excavations dated to the 17th century onwards are extremely rich in glass artefacts, with this being a reality from the north to the south of the territory. Contrasting with this reality, no glass production locations from this period have been discovered or excavated so far, which makes the provenance attribution a challenging endeavour. One specific archaeological location, the Monastery of Santa Clara-a-Velha in Coimbra, held one of the largest glass archaeological assemblages dated to the 17th century unearthed in Portugal so far. Due to the large variety of objects’ shapes, glass colours and decorative features, this assemblage is a valuable candidate to hold glass artefacts produced in Portugal. Lacking archaeological excavation on glass furnaces in Portugal, the study of glassmaking raw materials is the most promising research line to investigate the provenance of glass circulating in Portugal. In this study, sand and pebbles from six different locations in the north/centre of Portugal were collected and melted to produce glass samples. The resulting glass samples were chemically characterised using LA-ICP-MS, to obtain the composition of the samples in major, minor and trace elements. The obtained results were compared with the composition of 37 historical samples from the Monastery of Santa Clara-a-Velha previously studied. Additionally, the thermal properties of selected synthesised glasses were analysed by Differential Scanning Calorimetry, allowing new insights on melting temperatures and glass workability. Results indicate that three artefacts with stylistic features attributed to a Portuguese production were locally made with sands collected in Coimbra. Full article

The contribution that materials science has made to the understanding of ancient glassmaking is unquestionable, as research undertaken in recent decades has extensively demonstrated. Archaeological glass is far from being a homogeneous class of materials, encompassing objects made for different uses, manufactured in different periods and geographic areas, with a variety of tools and working techniques. If all these factors are not adequately considered when approaching the study of ancient glasses from an archaeometric perspective, data obtained by analyses can incur the risk of being less informative or even misinterpreted. Moving from previously performed research, this paper is aimed at reflecting on the potential of synergistic approaches for the study of archeological glasses, based on the interrelation among different disciplines and fostering the integration of archaeological and historical knowledge with data-driven scientific analyses. Full article