THE X-RAY FLUORESCENCE ANALYSIS OF MEDIEVAL DURABLE BLUE SODA GLASS FROM YORK MINSTER

The chemical composition of durable blue soda glass dated to the twelfth century from York Minster, both from the windows and excavated within this building, has been determined by X-ray fluorescence spectrometry. The analytical data are compared with results from specimens of similar date, colour and composition from Old Sarum and Winchester in England and Chartres Cathedral in France. Multivariate analysis of the compositional data reveals that this unusual blue glass may be classified into three principal groups the possible origins of which are discussed. The specimens in one of them are of particular technological interest since they may have been produced from Roman, or slightly later, glass in a manner referred to by the twelfth century monk Theophilus. It is shown that medieval stained glass of the soda-lime-silicate type, vis-a-vis that containing potash as the predominant alkali, is not as rare as hitherto believed.     

RETHINKING THE SMALL PIG HORIZON AT YORK MINSTER

Summary.   The small pig horizon within the headquarters building of the legionary fortress of Eboracum (York) is a unique assemblage of early post-Roman animal bones. Originally interpreted as evidence of an impoverished Dark Age community scratching out a living within the ruined fortress, reinterpretation of this deposit suggests that it may be evidence of the economic power of a post-Roman elite conspicuously consuming suckling pig, perhaps in an echo of high-status Roman dietary preferences.     

SCIENTIFIC ANALYSIS OF ROMAN GLASS FROM AUGUSTA PRAETORIA

Fifty-five fragments of Roman glass from Augusta Praetoria (Aosta, Italy) were analysed by inductively coupled plasma optical emission spectroscopy determining 15 elements (Si, Na, Ca, Al, Fe, Mg, Mn, Ti, Sr, Ba, Cr, Ni, Cu, Co and Pb) on dissolved samples; in addition, potassium was determined by flame atomic absorption spectroscopy. The analytical results indicate that all the fragments, with one exception, are silica-soda-lime glasses; (he exception is a potash glass. Cluster analysis was performed on the analytical data by accounting for either 14 (all the elements searched for but Ni and Pb) or eight elements (after further removal of Si, Fe, Mn, Cr, Cu and Co from the data set). The results obtained indicate that, once colouring and decolouring agents are removed, the classification of the glasses seems to be mainly determined by chronology; separate groups within coeval fragments may indicate different provenances.     

SPECTROCHEMICAL ANALYSIS OF SOME MEDIAEV AL GLASS FRAGMENTS FROM CATALAN GOTHIC CHURCHES

AAS, FE and OES are each used in the analysis of thirteen samples of fragments of window glasses from three Catalan Gothic churches: Sta. Maria del Mar (Barcelona, Spain), Pedralbes Monastery (Barcelona, Spain) and Girona Cathedral (Spain). Two kinds of stained window glass are found. Special attention is paid to Co/Cu, Co/Ni and Cu/Ni ratios for blue glasses and Mn/Cu and Fe/Cu ratios for red glasses.     

CHEMICAL ANALYSIS OF GLASS BEADS FROM MEDIEVAL AL‐BASRA (MOROCCO)

This paper reports the results of elemental analysis, using laser ablation – inductively coupled plasma – mass spectrometry (LA–ICP–MS), of 30 glass beads from an assemblage of beads excavated at medieval al‐Basra, Morocco. Six chemical glass types are represented and their characteristics and geographical origins are discussed, with reference also to the techniques used to make the beads. The presence of numerous beads of lead–silica glasses is of particular interest. The morphological, technological and chemical analyses of the bead assemblage shed light on al‐Basra's trade connections.     

RAW MATERIALS OF GLASS FROM AMARNA AND IMPLICATIONS FOR THE ORIGINS OF EGYPTIAN GLASS*

Analysis has been conducted on 19 blue glasses from Amarna in Middle Egypt dated to around 1350 BC. The results suggest that these glasses fall into two distinct types: cobalt coloured glasses with a natron based alkali made from local Egyptian materials, and copper coloured glasses with a plant ash alkali, which follow a Mesopotamian tradition of glass making. It is suggested that at least some of this copper/plant ash glass is imported into Egypt during the Amarna period despite extensive local production of cobalt/natron glass. Existing analyses (Lilyquist and Brill 1995) of the earliest glass from the reign of Tuthmosis III (c. 1450 BC) suggest that during this period the same two types of glass are present. Local Egyptian cobalt and natron in these early glasses implies that, despite the lack of archaeological evidence for production sites, glass was produced from its raw materials in Egypt as early as the reign of Tuthmosis III.     

ANALYSIS OF FIRST MILLENNIUM bc GLASS VESSELS AND BEADS FROM THE PICHVNARI NECROPOLIS,GEORGIA*

The Pichvnari necropolis on the Black Sea coast of Georgia lies in an area known in the late first millennium as ‘Colchis’, on part of the trade route leading to the Orient. The burials of the necropolis date to the late fifth century bc and frequently contain grave goods, including extremely well‐preserved polychrome glass beads and core‐formed vessels. This paper presents a study of these vessels both stylistically and archaeologically and using SEM–WDS and LA–ICPMS. It reveals that the vessels have compositional differences that may point to multiple manufacturing sites. One of the vessels appears stylistically unique and may exhibit one of the earliest uses of manganese as a decolorizer. Major and minor element data for the vessels suggest that they may belong to the same ‘Levantine’ group as many Roman glass objects, suggesting that a source of sand on the coast of the Levant could have been used in their production. The beads clearly show glass with both natron‐ and plant ash‐based flux with distinct rare earth compositions, showing multiple sites of production, some of which were probably either in the Middle East or the Indian subcontinent.     

SCIENTIFIC ANALYSIS OF SEVENTH‐CENTURY GLASS FRAGMENTS FROM THE CRYPTA BALBI IN ROME*

Inductively coupled plasma emission spectroscopy, reflectance spectroscopy and X‐ray diffraction were used to study seventh‐century AD glass fragments from the Crypta Balbi in Rome. All the samples were found to be silica‐soda‐lime glasses. Iron determines the colour of blue‐green, green and yellow‐green transparent glasses; chemical composition suggests deliberate addition of iron and/or manganese in about half the samples. Copper was found as the main colourant in red, pale blue and blue‐green opaque fragments; elemental copper acts as an opacifier in red glass, and calcium antimonate in white, pale blue and blue‐green glasses. Detection of antimony in transparent fragments suggests recycling of opaque mosaic tesserae.     

THE ANALYSIS OF SECOND MILLENNIUM GLASS FROM EGYPT AND MESOPOTAMIA,PART 1: NEW WDS ANALYSES*

A recent analytical study by SEM–WDS was carried out on 226 glasses from the Late Bronze Age, analysing each of the glasses for a total of at least 22 elements, the largest such analytical study conducted on these glasses. The aim of the analysis was first to identify which elements were brought in with each of the raw materials and, second, to accurately characterize those raw materials. Since different glassmaking sites in Egypt and the Near East would probably use at least some local raw materials and these raw materials will vary slightly from site to site, this has potential for provenancing the glass. Analysis showed new patterns in the compositions of glass from the various sites and led to new conclusions about the supply of raw materials and personnel for the glass workshops. This forms the basis for further work by LA–ICPMS to be presented in part 2 of this paper.     

PINE RESINS AND POTTERY SEALING: ANALYSIS OF ABSORBED AND VISIBLE POTTERY RESIDUES FROM CENTRAL NEW YORK STATE*

Analysis was performed on absorbed and visible residues from 21 New York State prehistoric pottery sherds dating from 2905 ± 35 bp (Intcal04) (1256–998 cal bc ) to 425 ± 40 bp (Intcal04) (1417–1626 cal ad ). The use of pine resin was detected in 10 of 12 absorbed residue samples and 11 of 17 sherds subjected to visible residue analysis. It seems likely that the pots were resin‐sealed to make them more impermeable, constituting the first chemical evidence of extensive resin‐sealing in North America. A comparison of the results of absorbed and visible residues from eight of the sherds indicates that the two kinds of residue provide complementary evidence of vessel use.     

THE OPAQUE RED GLASS OF CELTIC ENAMELS FROM CONTINENTAL EUROPE

Opaque red glass was used in the Celtic world for enamels and inlays. Forty artefacts, of various dates and found in various places, have been sampled and studied. They all belong to the same type, a soda-lime-silica high lead glass coloured by crystals of cuprous oxide. There is only one subgroup: glass lumps from the Mont-Beuvray oppidum contain manganese, less iron, and less lead. This change could be the result of Roman influence. Although most of these glasses form a surprisingly homogeneous group, no conclusions as to their origin can be inferred from our present knowledge.     

NEUTRON ACTIVATION ANALYSIS OF SIXTEENTH- AND SEVENTEENTH-CENTURY EUROPEAN BLUE GLASS TRADE BEADS FROM THE EASTERN GREAT LAKES AREA OF NORTH AMERICA*

Sixteenth- and seventeenth-century European blue glass trade beads from aboriginal sites in the eastern Great Lakes area of North America have been analysed non-destructively using low neutron dose instrumental neutron activation analysis, so that the beads could be returned to their keepers. Dark blue (cobalt-coloured) beads are readily separable from turquoise (copper-coloured) beads. Differences in the chemistries of the turquoise blue beads appear to be useful in separating glass beads from the two centuries. Low calcium, sixteenth-century turquoise beads tend to distintegrate by a leaching of the alkali metals.     

STAINING OF ARCHAEOLOGICAL GLASS FROM MANGANESE‐RICH ENVIRONMENTS*

It has been suggested that both internal and external sources of manganese may produce the black or brown staining that often occurs in buried archaeological glass. Modern potash glass of a manganese‐free medieval composition was scratched, etched and immersed in an aqueous solution containing dissolved manganese. After several weeks, immersion samples were sectioned and examined by SEM–EDX. Manganese was shown to be present in fissures and cracks within in the glass, where alkali had been depleted. Manganese from an external source is capable of blackening buried medieval potash glass.     

NEUTRON ACTIVATION ANALYSIS OF AD 1660–1930 EUROPEAN COPPER-COLOURED BLUE GLASS TRADE BEADS FROM ONTARIO,CANADA

Blue glass trade beads from well-dated late seventeenth- to early twentieth-century sites and collections have been analysed non-destructively by instrumental neutron activation analysis. The beads display enough variations in their elemental contents to allow us to characterize the different chemistries. The implication of these results is that similar chemical analyses of blue beads from undated archaeological sites may be used to help date the sites, since each bead chemistry has a specific earliest period.     

ARCHAEOMETRICAL STUDIES OF ROMAN IMPERIAL AGE GLASS FROM CANTON TICINO*

An archaeometrical study of Roman glass finds recovered in the Canton Ticino area was performed after the finding of traces of possible glass‐working at Muralto near Locarno. The aim of this work is to provide chemical characterization of these glass varieties—never analysed before—and to compare the results obtained with those for glass of the same period coming from other sites (Aquileia, Augusta Praetoria and Modena). The chemical data shows that the composition of Canton Ticino glass remained the same from the first to the fourth century ad . Moreover, the large amounts of Sb used as a decolouring agent in these samples represents a peculiar trait.