The Ancient Monuments Laboratory, Conservation

The Ancient Monuments Laboratory

Conservation

Investigations have continued into the nature of the waterlogged burial environment and the changes that might affect the preservation of organic materials. Monitoring is now being undertaken at Willingham/Over near Cambridge in advance of a major gravel extraction programme. The initial results show up the effects of different soils: the Willingham/Over site has a topsoil of heavy organic clay silt over sandy loam and silty sand with soil moisture high in the topsoil and low in the sandy layers over the watertable. In contrast, the soil at our monitoring station at Market Deeping is more uniformly sandy loam throughout the profile, with lower soil moisture in the topsoil than at depth.

Research has been commissioned from Durham University to investigate further the nature of the anaerobic environment and the methods used to measure it; this is showing the variability in different waterlogged environments in respect of their pH and redox potential. How some of these results translate into actual preservation conditions will be seen in the forthcoming evaluations at the Sweet Track. We have also undertaken a preliminary study of the effects of sewage on waterlogged environments at Flag Fen, in collaboration with the Robens Institute at Surrey University, work also supported by Anglia Water.

In collaboration with colleagues we are seeking minimally interventive solutions to preserve exposed archaeological sites as visitor attractions. A new preservation hall has been built at Flag Fen in which a section of the wooden structure has been exposed. We have assisted in the design of the spraying system, incorporating a silver ion injection system to inhibit bacterial and algal activity.

At Brading on the Isle of Wight the mosaics exposed for about 100 years under a covering building are deteriorating. The floors have been subjected to floods, they have suffered from algal growth when damp and from salt crystallisation when dry, and are buckling. We are working with others, including the Brading Roman Villa Trust, to devise a conservation programme that will enable us to retain the floors in situ and avoid the loss of character that would result from lifting and relaying them. Our contribution involves some novel environmental monitoring including that of the soil moisture content to assess the effectiveness of measures taken to improve groundwater drainage.

A series of seminars on Finds and Conservation was held during the year to encourage dialogue between conservators and finds personnel and lead to a better understanding between the two disciplines. The team of archaeological conservators and the Technology Section produced notes to accompany the seminars and demonstrated topics including marking, storage and packaging, agents of decay, on-site lifting, and aspects of technology. Questionnaires issued after each meeting enabled us to adapt future ones, X-radiography and current conservation practice proving particularly popular topics. Comments also showed that the participants found the days useful and interesting and they stimulated many interesting discussions.

Conservation assessments were carried out on material from two large projects, the Roman York project and the Roman site at Elms Farm, Essex. The latter has initiated discussions on the production of a computer programme for rapid conservation assessment where large quantities of artefacts are involved. Advice and assistance continued to be given during the pre-treatment phase of the Dover boat. Among waterlogged wooden artefacts being treated in the laboratory is an early wheel from Flag Fen which has been placed in a pre-treatment solution prior to freeze drying. A replica was made of a copper alloy spearhead from Flag Fen for display as the original was too vulnerable for this purpose. Artefacts from Birdoswald have also been replicated for display at that site, including gemstone intaglios, bone, and metal artefacts.

A study of the organic material associated with the metalwork from the Anglo-Saxon cemetery at Barrington, Cambridgeshire, is now under way. The site has produced two bed burials and the evidence preserved on the fittings suggests that they were originally complex wooden structures lined with textile. A Bronze Age dagger from Gravelly Guy has also been examined and the organic remains indicate that it originally had a two piece horn hilt with an antler pommel.