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The team assesses and analyses finds from excavations to increase knowledge of the materials and techniques used in their manufacture, and to reveal the skills and craftsmanship of the people who used them. Mostly we rely on visual examination and our experience of other objects previously examined, but radiography is an important tool which enables us to see the shape of the object beneath the concealing corrosion and soil accretions. Coupled with judicious removal of the accretions, these techniques, referred to as investigative conservation, are currently being applied to material recovered from the Middle Saxon settlement at Flixborough (North Lincolnshire). This includes the study of the hoard of carpenter's tools which were recovered after the completion of the excavation; they are well preserved with remains of wooden handles still present in many of the sockets. The preservation of organic materials on the metal artefacts from this site is more extensive than expected, especially on the iron, and it is hoped that the examination and identification of these remains will complement the work that has already been carried out on Saxon cemetery material. Another opportunity to look at the phenomenon of mineral preservation of organic materials in a more controlled environment has been provided by the experimental earthwork on Morden Bog, Wareham, Dorset, where leather with metal discs placed on the surface was buried when the earthwork was constructed. Radiography of the samples excavated after 32 years has shown that the steel discs have corroded extensively and the corrosion has spread through the leather. Further study of the recovered samples will enable us to understand better the mineralisation process.
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At Ingleby Barwick, Cleveland, part of an early Bronze Age inhumation was recovered using a freeze lifting technique. Working with colleagues from Durham University, the soil matrix was frozen using solid carbon dioxide and this enabled the inhumation to be lifted intact. Subsequent excavation in the controlled conditions of the laboratory enabled the precise location of the jet beads and metal artefacts buried with the body. Personal items from another burial, this time an Iron Age female grave at Portesham, Dorset, have also been investigated. The finds included a number of brooches and an engraved mirror which was examined in conjunction with our colleagues from the Technology Team. They analysed its component parts and showed it was high tin bronze, though the minor elements present indicated multiple sources for the metal.
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The team has been closely involved in all stages of the recovery and conservation of the Bronze Age boat from Dover, and the freeze drying, which was undertaken by the Mary Rose Trust, has now been completed. The next stage will be the reconstruction of the boat on a supporting cradle. Tests are being carried out to determine how different materials react to contact with the conserved wood. This has enabled us to identify a much cheaper alternative to the titanium which was originally specified as the least prone to corrosion, but we were surprised to discover that polyethylene glycol treated freeze-dried wood is aggressive to many materials. With the approval of the Dover Boat Trust's application to the Heritage Lottery Fund for the development of a purpose built display gallery in Dover Museum for the boat, we look forward to the successful completion of this project, one of the few that the Laboratory will have been involved in from the first discovery through to the final display, and one which will have been completed more quickly than that of any previously recovered boat remains.
Waterlogged wood: guidelines on the recording, sampling, conservation, and curation of waterlogged wood were published in August 1996 to coincide with the conference of the International Council of Museums Conservation Committee (ICOM-CC) Working Group on Wet Organic Archaeological Materials, which was held in York. Delegates from many countries around the world attended and five members of the team presented papers on their current research.
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