A Great Big Melting Pot: Exploring Patterns of Glass Supply, Consumption and Recycling in Roman Coppergate, York*

Abstract

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...

Glassmaking using natron from el-Barnugi (Egypt); Pliny and the Roman glass industry

“…The composition also confirms that the trona was the only significant reactive component in the natron. The glass produced mimics a typical Roman glass composition of the first to third centuries (Jackson and Paynter 2015), which suggests that such a glass can easily be produced at temperatures of 1100°C using these proportions of raw materials in a single stage without natron pre-treatment. Some chlorine is present from the sodium chloride, which is known to aid the glass forming process, and SO 3 from the sodium sulphate.…”

A Mosaic of Colors: Investigating Production Technologies of Roman Glass Tesserae from Northeastern Italy

“…The reduced compositions are then compared against literature compositional groups for the period of interest; in particular, the main compositional groups dominating the Roman period (1st-3rd century AD) are Sb-colorless, Mn-colorless, Sb/Mn colorless, and unintentionally colored glass. They differ in antimony and manganese contents, being Sb-colorless characterized by high antimony content (Sb 2 O 3 = 0.81 ± 0.16 wt %) and no manganese, Mn-colorless by very high manganese (MnO = 1.41 ± 0.27 wt %) and no antimony, Sb/Mn colorless glass by the presence of both manganese (MnO = 0.41 ± 0.16 wt %) and antimony (Sb 2 O 3 = 0.43 ± 0.15 wt %), and unintentionally colored glass by generally low manganese (MnO < 1 wt %) and negligible antimony [37][38][39]. In addition to different ratios of manganese and antimony, which are not considered in the reduced compositions, the other key characteristics of these groups are the different contents of SiO 2 , Na 2 O, CaO and Al 2 O 3 [37,39]: Sb-colorless glass is characterized by high silica and soda (SiO 2 : 69 ÷ 73 wt %; Na 2 O: 18.5 ÷ 20.5 wt %) and low lime and alumina (CaO: 4 ÷ 5.5 wt % and Al 2 O 3 : 1.6 ÷ 2.2 wt %), Mn-colorless and unintentionally colored glass by low silica and soda (SiO 2 : 67 ÷ 71 wt %; Na 2 O: 14.5 ÷ 17 wt %) and high lime and alumina (CaO: 7 ÷ 9. wt % and Al 2 O 3 : 2.5 ÷ 3 wt %), and Sb/Mn colorless glass by intermediate contents of the above elements (SiO 2 : 68.5 ÷ 71 wt %; Na 2 O: 16.5 ÷ 18.5 wt %; CaO: 5.5 ÷ 7 wt %; Al 2 O 3 : 2 ÷ 2.5 wt %).…”

Characterization of Roman glass tesserae from the Coriglia excavation site (Italy) via energy-dispersive X-ray fluorescence spectrometry and Raman spectroscopy

“…(KNa) 2? (SO 4 ) 2 4-being the model compound, in which a partial substitution with Co may be possible. In this study, from the EDXRF measurements we can observe that cobalt was not present, or only in very small amounts making it not detectable.…”

“…Glasses are commonly found within archeological excavation sites in various forms from large vessels to jewelry to small tesserae cubes used to construct mosaics [1][2][3][4].…”

“…Recent examples include X-ray fluorescence spectrometry [9][10][11][12], Raman spectroscopy [12,13], inductively coupled plasma mass spectrometry [1], laser ablation inductively coupled plasma mass spectrometry [7,14,15], inductively coupled plasma atomic emission spectroscopy [2], scanning electron microscopy with energy-dispersive X-ray spectroscopy [3,7,11,16], X-ray photoelectron spectroscopy [10], particle-induced X-ray/ gamma ray emission [3,10], laser-induced breakdown spectroscopy [17,18], electron microprobe analysis [16,19], and X-ray powder diffraction [16]. Some of these studies were conducted with portable instrumentation, thus permitting on-site and/or in situ analyses of the artifacts [9][10][11][12][13]20].…”