Aspects of the Production of Cobalt‐blue Glass in Egypt

Cobalt‐blue glass of the Near and Middle Eastern Late Bronze Age has long been recognized as compositionally distinct from other contemporary glasses (Sayre 1967; Lilyquist et al. 1993). It has been suggested recently by Shortland and Tite (2000) that this chemical distinction reflects the use of Egyptian raw materials for making these glasses, different from those used to make glass in Mesopotamia, or its manufacture by Mesopotamian workmen, possibly in Egypt. This assumed that cobalt‐bearing alum from the Western Oases and mineral natron from the Wadi Natrun were used for the cobalt‐blue glass, while the other, probably Mesopotamian, glasses were made using plant ash as the main alkali source. This note discusses some technical aspects of the possible ways in which the cobalt could have been added to the glass, and how this relates to the likely raw glass used in its making. Combining earlier suggestions by Noll (1981) and Brill in Lilyquist et al. (1993), an alternative explanation of the chemical characteristics is suggested, maintaining that all the glasses under discussion were made using plant ash. Differences in alkali concentrations probably reflect different soil and plant chemistries, and the colorant was probably added to the glass after being precipitated from the alum as a complex cobalt aluminium hydroxide.     

STATISTICAL EVALUATION OF THE PRESENTLY ACCUMULATED LEAD ISOTOPE DATA FROM ANATOLIA AND SURROUNDING REGIONS

Several hundred new stable lead isotope ratio determinations of ore and slag specimens from ancient mining sites throughout Anatolia and of samples of artefacts of the Chalcolithic, Bronze Age and Early Iron Age from museum collections in Turkey and the United States have been combined with the accumulated published isotope determinations of such specimens from throughout the eastern Mediterranean and Aegean regions to form a data base of nearly 1000 analyses. It is the purpose of this paper to evaluate the practical effectiveness of using this now extensive data base to discriminate between the many sources of metals throughout this region and to propose methods to enhance this discrimination. By using the full three-dimensional isotopic data in multivariate statistical treatments and by separating isotopically resolvable source groups within some of the source areas and isolating statistically outlying specimens from them, it has been possible to characterize some ore sources more precisely and compactly and thereby achieve better resolution between ore sources. It has also been possible to isolate isotopically compatible artefact groups which possibly relate to ore sources that, as yet, have not been well defined by isotopic analysis.     

CHEMICAL COMPOSITION OF A BOG BODY ADIPOCERE

Chemical analyses were carried out on adipocere obtained from a bog body recovered from a peat bog at Meenybradden, County Donegal, Ireland. Chromatographic (thin-layer chromatography and gas chromatography) and mass spectrometric analyses, combined with microanalytical chemical transformations, have yielded detailed compositional information. An absence of intact triacylglycerols, diacylglycerols and monoacylglycerols indicates that hydrolysis is complete. Consequently the adipocere is composed mainly of fatty carboxylic acids. The high proportion of palmitic and stearic acids, together with depleted oleic acid content, indicates that extensive reduction and, possibly, β-oxidation have occurred during burial in the peat bog. Hydration of the double-bond in oleic acid has also occurred, as is shown by the formation of 10-hydroxystearic acid. The monoenoic fatty carboxylic acids that are present, composed mainly of C₁₈ and C₁₆ compounds, comprise a mixture of positional isomers. The results are compared and contrasted with those obtained from previous studies of the lipid composition of other adipoceres and cadavers of archaeological interest.     

EVIDENCE FOR THE MIXING OF FATS AND WAXES IN ARCHAEOLOGICAL CERAMICS

Lipid residues from two Late Saxon/early medieval ceramic vessels recovered from excavations at West Cotton, Raunds, Northamptonshire, U.K., have been investigated by high-temperature gas chromatography (GC) and GC/mass spectrometry (GC/MS). The solvent extracts of sherds sampled from different points on each vessel (i.e., base, body and rim) were analysed quantitatively and qualitatively and compounds were identified which were characteristic of beeswax and animal fat. Furthermore, by determining the sites of accumulation of the specific lipid types and their concentrations in different parts of the vessels it can be inferred that the beeswax was added to the vessels prior to the addition of the fat. It was concluded that the two vessels performed different functions in antiquity.     

SHRINES AND CERAMICS IN CHALCOLITHIC ISRAEL: THE VIEW THROUGH THE PETROGRAPHIC MICROSCOPE

The question of the nature of social and economic life in the Chalcolithic southern Levant has recently been the subject of increasing interest. Several archaeological sites and features in Israel have been interpreted as elements of religion. These include the shrines at En-Gedi and Gilat and the Nahal Mishmar hoard. The results of petrographic analyses of the pottery assemblages of these three sites, as well as the ceramic cores of copper artefacts from Nahal Mishmar and additional sites, are presented. In light of these results some previous hypotheses are tested. Alternative suggestions are offered as to the role of these sites in the life of the inhabitants of the Chalcolithic southern Levant.     

QUANTIFICATION AND DISTRIBUTION OF LIPID IN ARCHAEOLOGICAL CERAMICS: IMPLICATIONS FOR SAMPLING POTSHERDS FOR ORGANIC RESIDUE ANALYSIS AND THE CLASSIFICATION OF VESSEL USE

Organic residue analysis has been performed on 62 reconstructed vessels from a single archaeological site (Rounds, Northamptonshire, U.K.). In order to establish regions of lipid accumulation within a vessel, sherds were sampled from different parts of a vessel, for example base, body and rim, and submitted to lipid extraction procedures. The techniques of high-temperature gas chromatography (GC) and GC/mass spectrometry (GC/MS) were then used to analyse the sherd lipid extracts. The quantitative results obtained show differential accumulation and preservation of lipid in various parts of the same vessel. This latter observation has serious implications for the sampling of potsherds for organic residue analysis. Furthermore, the amount of absorbed lipid varies quite considerably between vessel types. On this basis, a new method is proposed for classifying vessel use by comparing the concentration of lipid present in different parts of individual vessels.     

Rationales in Old World Base Glass Compositions

It is long known that most Egyptian and Roman base glass compositions show a remarkably small scatter in their chemical composition. By plotting appropriately reduced base glass compositions in ternary phase diagrams it is demonstrated that the compositional fields defined by the compositional scatter are closely related to eutectic regions within the relevant phase diagrams. This is interpreted as to be due to an eutectic melting regime, i.e. partial melting in the presence of a crystalline buffer or residuum, and not primarily a result of strict recipe and raw material control. Furthermore, it is demonstrated that possibly two independent melting temperature indicators are correlated, suggesting a factual relationship between melting temperature and melt composition. This evidence is taken to develop a “partial batch melting model” for these early glasses, as opposed to the “total batch melting model” of Mediaeval and early modern glasses. Some archaeological implications of this model are briefly discussed.     

A COMPARISON OF METHODS FOR ESTABLISHING FATTY ACID CONCENTRATION GRADIENTS ACROSS POTSHERDS: A CASE STUDY USING LATE BRONZE AGE CANAANITE AMPHORAE*

Canaanite amphorae fragments in fabrics believed to be associated with the bulk transport of vegetable oils from the fourteenth‐century BC site of Amarna, Egypt, have been examined. A comparison is made between solvent extraction, saponification and the use of TMTFTH (m‐trifluoromethylphenyl)trimethylammomum hydroxide, used here for the combined extraction and derivatization of ceramic‐absorbed organic residues. Extracts were studied using gas chromatography and gas chromatography‐mass spectrometry. The extraction of fatty acids from small ceramic samples has established concentration gradients of absorbed organic matter from the inner to the outer surfaces of the sherds.     

Glass Fragments from the Crypta Balbi in Rome: the Composition of Eighth‐century Fragments

Eighth‐century glass fragments from the Crypta Balbi in Rome were analysed by inductively coupled plasma emission spectroscopy. The samples included fragments of artefacts as well as ingots of raw glass and wasters. All the fragments proved to be soda–lime glasses. Manganese‐to‐iron atomic ratios are highly variable and determine the colour of a large number of samples. Fairly high copper contents, generally associated with relatively high amounts of antimony and lead, were detected in some green and blue–green samples: this suggests recycling of glass in the form of opaque mosaic tesserae. All three elements are higher in eighth‐century than in previously analysed seventh‐century fragments. This may indicate greater recourse to recycled glass, related to a reduction in trade exchanges in the Mediterranean.     

DIRECT EVIDENCE OF PRIMARY GLASS PRODUCTION IN LATE BRONZE AGE AMARNA,EGYPT

This paper presents direct archaeological evidence for the primary production of glass at the LBA site of Tell el‐Amarna, in the form of numerous finds of semi‐finished glass. The diagnostic microstructural and chemical composition of these finds is presented alongside macroscopically similar finds, of shapeless lumps of finished white glass. The semi‐finished glass was found to contain numerous inclusions of residual quartz and newly formed lime‐rich crystal phases, but no added colorant. However, several samples of semi‐finished glass have antimony oxide levels comparable to those of finished white glass, suggesting that the opacifier was added to the initial glass‐making batch. The results are discussed in comparison with the evidence for glass‐making from Qantir – Pi‐Ramesse, identifying some close technical similarities, which indicate that the same technological processes were used at both sites for the production of glass.