One hundred and ninety three glass fragments from the canabae in York were analysed (first to fourth centuries). They fall into six compositional groups: antimony colourless (Sb), highmanganese (high-Mn), low-manganese (low-Mn), mixed antimony and manganese (Sb-Mn), high iron, manganese and titanium (HIMT) and plant ash. Some groups represent production groups, some of which appear to be in limited supply in this western outpost, but are more prevalent elsewhere, and others reflect changing supply mechanisms. The majority of glasses fall into groups that demonstrate extensive recycling of glass. This has important implications for determining provenance using trace elements and isotopes. KEYWORDS: ROMAN GLASS, NATURALLY COLOURED, COLOURLESS, ANTIMONY, MANGANESE, PRODUCTION GROUPS, RECYCLING, BRITAIN, ICP-AES THE ROMAN GLASS FROM COPPERGATEAlthough perhaps best known for its Viking deposits (Hall 1984), the site at 16-22 Coppergate, York also produced deposits rich in Roman finds, including glass. The putative glass-making or glassworking remains have already been published (Jackson et al. 2003), but the site also yielded a large assemblage of glass fragments, typical of a consumption assemblage from the first to fourth centuries and which is probably unrelated to the glassworking debris found at the site (Jackson 1992). The assemblage comprises forms that can be dated from the first to fourth centuries and represents a microcosm of glass found in the western provinces at this period. The scale of the assemblage is not surprising: Eboracum (Roman York) was an important Roman centre in Britain, occupied from ad 71 to 410, housing a fortress and large manufacturing and civilian districts. Coppergate was outside the fortress, within the city walls, and is likely to have been a trading or manufacturing area as part of the canabae, although Roman remains from the site have been largely robbed (Mainman 1990). Within scientific research into Roman glass, the composition of colourless glass has been well studied, as has later glass from the mid-third and fourth centuries onwards (e.g., Freestone et al. 2005;Jackson 2005;Paynter 2006;Silvestri et al. 2008; Jackson 2009, 2010;Gallo et al. 2013), but naturally coloured glass of the first to third centuries has often been neglected. 'Naturally coloured' here describes transparent glass with a range of mostly 58, 1 (2016) 68-95blue-green hues caused by small amounts of iron oxide in the glass (Price and Cottam 1998), as opposed to containing intentionally added colourants. The Coppergate assemblage is significant because it includes naturally coloured, as well as colourless, glass in many common forms from a long-lived site, including many fragments that date from the second and third centuries. This study is therefore able to analyse a large corpus of material from a single site to demonstrate the availability of different raw glass types, and the extent of recycled glass within the trading network operating throughout the Roman world. By identifying changing glass composi...

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This study highlights regional variation in the composition of iron‐smelting slag produced in England prior to the medieval period and attempts to link slag composition to the type of ore smelted. For many sites, the slag compositions were consistent with the use of limonite ore, but there is evidence that siderite ore was smelted at sites in Sussex in the late Iron Age/Romano‐British periods. A compositional comparison of smelting slags and slag inclusions in Iron Age currency bars, using data from Hedges and Salter (1979), illustrates the potential of smelting slag compositional data in provenance studies of early iron objects.

A collection of tesserae and two fragments from rounded cakes of coloured glass, probably dating to the 2nd century AD, were found at West Clacton Reservoir, Essex, in the UK, by Colchester Archaeological Trust. A selection of the finds were analysed using SEM-EDS and ICP-MS. This paper provides data on the composition of the different glass colours and discusses how each colour was made. Colourants and opacifiers were added to a base glass, most often one of the transparent, naturally coloured (blue-green) natron glass types widely available at the time, but there appear to be preferences in the type of base glass used for certain colours, which affects the type of antimonate opacifier precipitated. Possible reasons for using different types of base glass to make strongly coloured Roman glass are discussed.

Previous research has established that Iznik pottery differs from other Islamic stonepaste pottery in that its stonepaste bodies contain lead oxide as well as soda and lime, and that a significant proportion of the tin oxide in its glaze is present in solution rather than as tin oxide particles. In order to better understand these distinguishing features, the chemical compositions and microstructures of Iznik pottery and tile samples, together with those of lumps of glass found in association, were investigated using both scanning electron and optical microscopy. These data have been supplemented by the study of replicate lead-alkali glazes produced in the laboratory with a range of different compositions. The results demonstrate that separate soda-lime and high-lead glasses were used in the production of Iznik stonepaste bodies, and that the total glass contents of the bodies were significantly higher than those quoted by Ab ¨ 'l-Q å sim, who was writing in about AD 1300. The very high purity of the lead-soda Iznik glazes indicated that the alkali flux used was either a purified plant ash or an as yet unidentified mineral source of soda. Replication experiments established that the high solubility of tin oxide in the glaze was due to the high purity of the glaze constituents. Furthermore, it is suggested that tin oxide was added to the glaze in order to give it a very slight opacity and thus obscure any blemishes in the underlying body.

In the Near East and Egypt, vitreous materials in the form of glazed stones and faience were first produced from about the 4th millennium B.C. Subsequently, the period around 1500 BC saw major developments in the range of vitreous materials with the production of glass vessels and glazed clay objects and an extension in the range of colorants used. This paper first describes how the examination of artifacts has been used to reconstruct the processes involved in the production of these different vitreous materials. This information is then used to try to understand how the new technologies were discovered and why they were adopted.

This paper discusses the development of Roman antimony decolourised natron glass, its dominance, and subsequent decline, using new trace element data for colourless glass found in Britain. Experimental glasses are used to investigate the influence of different proportions of raw materials (particularly the ratio of natron to calcium carbonate) on the resulting transparency or opacity of glass when antimony is added. Focusing on the 1st to 3rd centuries AD, the study has found that (1) There are chronological differences in antimony colourless glass compositions including (a) some early vessels have abnormally low calcium, aluminium and barium levels; (b) 1st/mid-2nd-century AD vessels in Britain may also contain up to 0.6 wt% lead oxide whereas mid-2nd/3rd-century AD vessels contain less than 300 ppm, and (c) the antimony content tends to decline over time. (2) These developments can be linked to production and recycling practices; but trace elements suggest that all of these antimony colourless glasses share an origin, probably Egypt. (3) Crucially, production of experimental glasses illustrates the inherent suitability of a sodium-rich, calcium-poor base glass composition for making antimony colourless glass, as it readily dissolves added antimony; conversely lower-sodium, higher-calcium glasses start to form opacifying calcium-antimonate crystals with the same quantities of antimony. Thus, the sodium-rich, calcium-poor glass composition from Egypt was ideally suited for decolourising with antimony and formed a water-clear glass. The calcium-rich Syro-Palestine glasses were more easily opacified with antimony to make opaque glass, but were decolourised with manganese, not antimony.

As part of a multidisciplinary programme of research on Islamic glazed pottery, the development of polychrome decoration during the 12th century AD has been investigated by examining polished sections through glazed pottery in an analytical scanning electron microscope. The two main decorative techniques used were underglaze and overglaze painting. The results suggest that true underglaze decoration, involving the application of pigment without any associated slip, was ®rst developed in Syria, from where it spread to Iran, on to China and ultimately across wide areas of the world. In contrast, the overglaze technique used on mina'i ware was both very short-lived and con®ned to Iran. The analytical results suggest that the probable explanation for this was the technical problems associated with maturing the overglaze paint and the consequent risk of unsatisfactory products.