Highlights of the year include the acquisition of a new Scanning Electron Microscope (SEM) with Energy Dispersive X-ray Analysis (EDXA), and its use on current research projects examining silver refining debris and the analysis of punchmarks on Saxon metalwork. We have also published guidelines for archaeometallurgy, have successfully organised a conference on pre-industrial glassworking, and have established training sessions on archaeotechnology for archaeologists.
The new SEM is now being widely used by staff from different sections and by visiting researchers for a variety of applications, including the study of corrosion products on glass and metals and the examination of fibres and textiles. Using some of the more advanced functions of the equipment, decorative punchmarks on Anglo-Saxon metal artefacts are being recorded and analysed. This information on decorative practices will form part of the technological study of these objects. The debris from silver refining is now easily recognised but the exact details of the processes involved are not so well understood. Investigation of finds from a number of Roman and medieval sites using the new SEM, in collaboration with a German research fellow, have unravelled many of the mysteries, but also posed additional questions.
Petrological analysis of the only sherd of pottery associated with the Dover Bronze Age boat has shown that the clay fabric contained frequent irregular-sized pieces of grog (crushed pottery). Several of these fragments contained small fragments of lighter-coloured grog within them, demonstrating an early form of recycling. Grog-tempered pottery, which was common in the Bronze Age, is usually difficult to source. However, frequent microfossils were visible in the thin section and these are being studied in collaboration with the British Museum (Natural History) to see if it is possible to say whether the pot was made on the British or continental side of the Channel.
Ancient technology has often been seen as the Cinderella of the archaeological sciences, though nowadays most archaeologists are aware that it can show how and where objects were made. In order to capitalise on this increasing interest and awareness, guidelines were published jointly with the Historical Metallurgy Society, demonstrating the benefits of treating metallurgical studies as an integral part of most archaeological projects. The demand for information on metalworking evidence has been met by the production, again in conjunction with the Historical Metallurgy Society, of a series of data sheets which provide back-up for sessions of practical training in the identification of slags and other metallurgical debris.
Examination and identification of metalworking debris continued. An in-depth study was completed on a range of residues from an historical blast furnace at Rockley, South Yorkshire. The aim was a better understanding of the important transition from charcoal to coke smelting, which the Rockley furnace appears to have successfully spanned. An unexpected outcome of the analytical programme was the realisation that an additional manganese-rich `ingredient' was missing from the raw materials found during the excavation. This almost certainly points to the re-smelting of slag from an earlier bloomery furnace, which would have provided a valuable supplement to the ore.
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SEM image of a section through silver refining debris showing dark bone
ash particles surrounded by a mixture of pale lead-copper oxides and white lead oxide
(litharge) crystals
Thin section of grog-tempered pottery from the Dover boat