British Middle and Late Bronze Age Metalwork: Some Reanalyses

Abstract

IntroductionA study of major importance for our understanding of the composition of bronze artefacts of the Middle and Late Bronze Ages in Britain is the group of 438 analyses carried out by optical emission spectrometry by Brown and Blin-Stoyle (1959). Their description of the project and its conclusions were presented in that paper, and in a subsequent paper by Blin-Stoyle (1 959) the full analytical results for nine elements were published together with a comprehensive description of the emission spectrometry procedure which followed. The aim of the study was to look for perceptible variations in metal composition which might correlate with changes of bronze types or with the successive industries of the archaeological sequence. One of their findings which was of major importance was that there was a clear technological distinction between MiddIe and Late Bronze material, namely the presence of substantial lead concentrations in the Late as opposed to the Middle Bronze Age when lead was present in the bronzes in only minor, i.e. accidental, concentrations. The Late Bronze material was clearly intended to contain a substantial deliberate addition of lead to the bronze, resulting in easier casting properties including a lower melting point for the alloy.The technique of emission spectrometry has played an important part in the development of archaeological science, being capable of analysing for a wide range of both elements and concentrations of elements in ancient artefacts. Tite (1972) has discussed its applications to both metals and non-metals in archaeology, Britton and Richards (1969) have reviewed its particular application to the study of metallurgy in the European Bronze Age while both give accounts of the principles and practice of emission spectrometry for these particular applications. The initial setting-up of the spectrochemical procedure, including standardisation of the arcing conditions and calibration with standards is an elaborate process, resulting in typical reproducibilities of better that f. 25% (Freeth 1969).During the course of further research into Middle and Late Bronze Age artefacts, Mrs M. A. Brown, one of the co-authors of the original major study on this subject, requested analyses on a number of artefacts in the collections of the Department of Prehistoric and Romano-British Antiquities at the British Museum, London and this resulted in atomic absorption analyses being made by the Research Laboratory at the Museum on drilled samples taken from these objects. The drillings were taken by the Research Laboratory using the same type of drill and yielding approximately the same weight of sample (10-20 mg) as used for the original work (Blin-Stoyle 1959); drillings from the first 1-2 mm were discarded to avoid the corroded metal surface of the bronzes. The intention in having these analyses made was to look for further examples of some of the distinctive subgroups (IIa and IIb: Brown and Blin-Stoyle 1959) found by emission spectrometry to have higher than average

THE METALLURGY of the WILBURTON HOARDS

“…The opportunity is also taken to publish a number of relevant analyses carried out in the Research Laboratory for Archaeology and History of Art in the University of Oxford in the early 1960's. It has since been suggested that some analyses made earlier in that laboratory (Brown and Blin-Stoyle 1959) used, at least in part, a wrong method for the determination of lead (Hughes 1979). However, re-analyses of some of the same material from the Selborne hoard for this project shows that there are several difficulties in accepting the Hughes analyses and the present analyses match those of Brown and Blin-Stoyle rather better.…”

“…This encourages the belief that it was in the Guilsfield area that lead entered the Wilburton distribution system, accumulating in thoseobjects where high lead contents were an advantage and being kept out of those where it was not desired. This pattern may have changed in the Ewart Park period with more lead sources being used and lead appearing in hoards (Lawson 1979). In the Wilburton period lead entered the system in finished objects and, at the end, in plate scrap.…”

The Production of Copper Alloys in Iron Age Britain

“…This alloy is broadly similar to that used in the Late Bronze Age (Brown & Blin-Stoyle 1959;Hughes 1979;Northover 1982a) while objects from the Iron Age proper (see below) only rarely contain appreciable amounts of lead. This alloy is broadly similar to that used in the Late Bronze Age (Brown & Blin-Stoyle 1959;Hughes 1979;Northover 1982a) while objects from the Iron Age proper (see below) only rarely contain appreciable amounts of lead.…”

Beyond Provenance

“…Because NAA is insensitive to lead, the Heidelberg lead analyses were conducted using isotope dilution mass spectrometry. As seen by Hughes (1979), there was a larger disagreement in lead concentration results between the earlier and later analyses. Although the overall impression from this comparison is good, we should note that agreement to within a factor of three is not a very high level of consistency.…”

“…As well as these 'round robins', where several laboratories are invited to analyse the same materials, a number of targeted data inter-comparisons have been carried out, with the specific objective of assessing whether data produced by one method can be directly compared with those produced by another. For example, Hughes (1979) reanalysed using AAS some Middle and Late Bronze Age objects previously measured by OES, reported in Brown and Blin-Stoyle (1959), and found comparability for the elements Sb, Ag, Ni, Bi, Fe, As. However, the disagreement in the concentration of lead by these two techniques was shown to be large.…”