Compositional identification of 6th c. AD glass from the Lower Danube

A group of finds (vessels, raw glass chunks, window panes) from three sites in present-day Bulgaria was selected as representative of the circulation and usage of glass in the Lower Danube region during the 6th c. AD. In total, 79 samples were analysed by EPMA and/or LA-ICP-MS techniques. The data quality was assessed for each analytical run according to the measurement of reference glasses and to pairs of results obtained from representative samples of archaeological glass analysed by both techniques. Combining EPMA and LA-ICP-MS data allowed a sufficiently consistent and unified set of primary results to be formed. As already suggested in an earlier preliminary paper, only a single glass composition was found to dominate the 6th c. contexts in the region. The current study recognises this 6th c. glass from the Lower Danube as identical with the so called 'Serie 2.1.' defined by D. Foy and co-workers (2003) in various assemblages in Southern France and North Africa. The major, minor and trace oxide evidence presented here indicates that this is a distinct primary glass composition, with an iron-rich sub-group tentatively differentiated within the main group. Accordingly, an attempt is made to situate it relative to the other main primary compositions in the region. The proposed interpretation is that the 6th c. glass should not be linked to the HIMT glass despite the nominal similarity between them due to their elevated iron oxide, manganese, and titania concentrations. Instead, a possible link between the geochemical characteristics of the 6th c. glass and an earlier group of manganese decolourised glass, equivalent to 'Serie 3.2.' outlined by D. Foy and co-workers (2003) is suggested. This may imply the use of sand from a broadly identical geological area, hence it is possible that both the 6th c. glass and the manganese decolourised composition are likely to share a common origin

The early Byzantine HIMT glass from Dichin, Northern Bulgaria / Ранновизантийско Стъкло тип HIMT от Градището При С. Дичин

The archaeological site of Dichin (named after the nearest modern village) is a relatively small but well-fortified settlement from the Late Roman/ Early Byzantine period. It is situated in present-day central Northern Bulgaria, district of Veliko Tarnovo, and lies about 10 km from the Roman town of Nicopolis ad Istrum (Fig. 1). The site has been excavated by a joint British-Bulgarian team in 1996- 2003. The dating of finds from Dichin is restricted to the 5th – 6th centuries AD with two main periods of occupation – ca AD 410-490 and ca AD 540-580 (Poulter 2007, 82-94; Динчев и др. 2009, 15-26). The excavations have produced numerous glass fragments, mostly of bowls, cups and beakers in a range of hues spanning from yellowish and “aqua”, i. e. natural light blue and transparent green to a more yellow amber colour, as well as few examples of coloured glass. In total, 119 fragments are studied in a detailed archaeological catalogue, separated into ca 15 categories and variants according to the morphological and typological features of the vessels, technique of their manufacture and decoration, and glass colour (Чолакова 2009). For this preliminary study, two different types of glass were selected – transparent green and olive-amber glass. Initially they were macroscopically differentiated as opposites on the basis of their colour, production techniques and quality. Both groups belong to the first main period of the site (5th century). These were studied as part of the post-excavation processing of finds, and a brief report on types and their chemical composition is presented here; a fuller programme of analysis and interpretation is currently under way. The current study focuses on ten fragments (samples G 1-3, G 11-17) found in the North-Western area of the site, excavated by the Bulgarian part of the team (Динчев и др. 2009)

Shape-Shifting Polyhedral Droplets

Cooled oil emulsion droplets in aqueous surfactant solution have been observed to flatten into a remarkable host of polygonal shapes with straight edges and sharp corners, but different driving mechanisms - (i) a partial phase transition of the liquid bulk oil into a plastic rotator phase near the droplet interface and (ii) buckling of the interfacially frozen surfactant monolayer enabled by drastic lowering of surface tension - have been proposed. Here, combining experiment and theory, we analyse the hitherto unexplored initial stages of the evolution of these 'shape-shifting' droplets, during which a polyhedral droplet flattens into a polygonal platelet under cooling and gravity. Using reflected-light microscopy, we reveal how icosahedral droplets evolve through an intermediate octahedral stage to flatten into hexagonal platelets. This behaviour is reproduced by a theoretical model of the phase transition mechanism, but the buckling mechanism can only reproduce the flattening if surface tension decreases by several orders of magnitude during cooling so that the flattening is driven by buoyancy. The analysis thus provides further evidence that the first mechanism underlies the 'shape-shifting' phenomena.Comment: 11 pages, 12 figure

Seventh to eleventh century CE glass from Northern Italy: between continuity and innovation

Previous analytical studies show that most of Northern Italian glass has been heavily recycled and that mixing of natron and plant ash glass was occurring (Verità and Toninato 1990; Verità et al. 2002; Uboldi and Verità 2003; Andreescu-Treadgold and Henderson 2006; Silvestri and Marcante 2011). The re-use of “old Roman glass” has been interpreted as stagnation in glass trade from the primary production areas. However, the reintroduction of plant ash glass on sites such as Torcello, Nogara, and in Lombardy at the same time as it was reintroduced in the Levant, strongly indicates long-distance contacts with the Levant at least from the eighth century CE. This paper addresses the key issue of recycling by focusing on the compositional nature of glass traded and reworked in Northern Italy after the seventh century CE set in a broad Mediterranean context by analysing major, minor, and trace elements in eighty-nine glass samples (seventh to the eleventh century AD) from the glass workshop of Piazza XX Settembre, Comacchio. Five major previously proposed compositional groups of glass have been identified from Comacchio (Levantine Apollonia and Jalame types, HIMT, Foy-2, and plant ash glass). The impact of recycling and mixing practices in Comacchio glass is also discussed with the help of known recycling markers and selected ratios (major and trace elements). The mixing between Levantine, HIMT, and plant ash glass is highlighted and end-members of potential natron to natron mixing compositional groups have been identified. The compositional nature of plant ash glass from Northern Italy is discussed in light of their trace element content and production areas