4.14 The Ancient Monuments Laboratory
Conservation
The Archaeological Conservation team continues to work with the Central Archaeology Service on their projects. X-ray fluorescence analysis has been carried out on the coins from Owmby, while some of the corrosion products from them have been analysed with X-ray diffraction in an attempt to understand the reason for the marked variation in condition within the collection. Packaging systems were devised for the brick and tile recovered from the fire-damaged areas at Windsor Castle for safe long-term storage. The bricks are important reference material and the system also had to ensure they could be used as a reference collection.
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Contributions to the Archaeology Commissions programme have included work during the analysis phase on material from Ickham and Elms Farm, where investigative conservation has been carried out on a collection of pewter vessels. The conservation of material from the Saxon settlement at Flixborough has been completed and work has continued on the examination of mineral-preserved organic material on the metal artefacts from the site. A third of the knives have remains of the handles, in most cases of horn, just like the evidence from Saxon cemeteries. Leather from their sheaths is also preserved in a few cases, one example being decorated with incised lines.
Work has also been undertaken on material from excavations at our own properties. Assessments have been completed on material from Wharram Percy and St Peter's Church, Barton upon Humber. The latter site produced a large number of coffin fittings and it was noted that some of the coffin plates are identical to examples found at Spitalfields in London. Remains of the wood from the coffins are preserved on the metal fittings and there is also evidence for textiles used as coverings and the remains of shrouds on pins and buttons; there is even a pair of earrings with traces of human hair. Conservation of material from Camber Castle has been completed and the site produced an interesting collection of jack plates, a form of armour, which have the remains of textile, padding, and even the stitches tat attached the plates to the fabric. Staff assisted the Historic Royal Palaces Agency to lift a fish trap that had been discovered in excavations in the moat of the Tower of London. The clay was carefully removed from the trap and an ingenious system of supporting the fragile structure devised. Another wooden find was an unusual implement with an integral handle and a notched end discovered at Yarnton, Oxfordshire, at the base of a well, and thought to be Bronze Age. Samples have been taken for radiocarbon dating and other possible analysis. Both these items are undergoing pre-treatment before freeze drying.
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A project analysing corrosion layers on iron artefacts from waterlogged sites found corrosion products that had contributed to the preservation of original surface marks and decoration even though the artefacts themselves had sometimes become voided. X-Ray diffraction analysis detected the iron sulphides mackinawite, greigite, and pyrite. Their formation requires anaerobic bacteria to reduce sulphates in soils to sulphides, which then create biogenic iron sulphide. They are thus indicative of waterlogged anoxic conditions, so their presence can be used as markers for these conditions, even on sites that are now dry.
Collections conservation
A major effort has been made this year to return archaeological archives held in our stores to the appropriate archive holders in advance of the relocation of the store's from Nottingham to Fort Cumberland. This has involved considerable research to identify the sites from which the material originated and to establish its ownership. As a result, several thousand boxes have been returned.
Continuing work begun in 1996, a condition audit of works of art on paper at Audley End has been carried out, and an audit of all the collections, fixtures, and fittings at Eltham Palace is in progress prior to major works on the building. In both cases the aim is to identify and prioritise the items most in need of conservation. This is done not only by assessing the condition of each item, but also by considering its importance in the context of the collection. A simple database enables lists of priority objects to be produced, together with estimates of time required and costs. Following our involvement with the Down House conservation project and the St Augustine's Abbey new museum project, we commissioned a report on the role of collections conservation in major projects managed by English Heritage. This identified a number of key issues that need to be addressed so that the team can offer an appropriate level of service to Major Projects without an undue impact on their other work.
We organised a training course on the identification of museum insect pests for 15 curators and custodians from all the Historic Properties regions. This has enabled them to monitor for insects in the properties for which they are responsible, identify the species present, and develop control strategies. The course was very well received by the participants and will serve as a model for future courses in collections conservation.
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It is very important to maintain an environment in historic houses that will be appropriate for the collections, the buildings themselves, and the people who visit and work in them. In the past very tight specifications were set for the environment in museums, but it is clear that it is almost impossible to achieve these in historic buildings, and there is very little information about how historic artefacts react to changes in their environment. In order to supply some of this basic data an experiment has been setup at Kenwood to record changes in weight in a chair as it absorbs and desorbs water, and simultaneously to monitor changes in width of part of the frame. These changes can be correlated with changes in the ambient temperature and relative humidity. Thus far, it is clear that this object hardly responds at all to changes in relative humidity lasting less than 24 hours, and is only affected by slower changes taking place over a period of several days. This experiment will be extended to other classes of artefact and to building fabric, and will eventually lead to the definition of more realistic ranges of relative humidity and rates of change, which will minimise damage to historic artefacts and buildings.
Wall painting conservation
Two exciting projects were initiated this year as part of our contract with the Courtauld Institute of Art. At Castle Acre Priory, Norfolk, the extent and condition of the medieval decoration in the Prior's Chapel was recorded.
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Here the remains of painting are extremely fragmentary but of very high quality and this project enabled an in-depth investigation to be made, including examination on-site using a video microscope. At Portchester Castle, Hampshire, extensive remains of an eighteenth-, or possibly nineteenth-century, decorative scheme survive on the second floor of the keep. The condition audit highlighted the serious condition of the painting, which consists of a large fictive hanging with decorative cartouches, one of which contains a depiction of Portchester Castle itself, possibly based on an engraving. The aim of this initial programme of conservation was to record the extent and condition of the surviving decoration and to undertake emergency remedial treatment to stabilise the painting. Cleaning and presentation issues will be addressed at a later stage. It has always been assumed that the scheme was painted by inmates when the castle was used as a prison during the Napoleonic Wars, and that it was painted as a theatre backdrop. This is not certain, however, and further research is being undertaken as part of this preliminary phase of conservation.
Architectural paint research
This year has seen yet another increase in demand for the service provided by the Architectural Paint Research Unit. The increased awareness of the potential of architectural paint research has been promoted by the recommendations of PPG-15 and architectural projects funded by the European Community and the National Lottery. English Heritage clearly has a strategic role to play in these projects, identifying paint research needs, preparing briefs, and monitoring research consultants. Over the past months the unit has been closely involved in a wide variety of joint funded schemes, which has included the restoration the Reading Room of the British Museum, the plans for the redisplay of the Russell Coates Museum at Bournemouth, and the opening of the Assize Court, Bodmin as a living history museum.
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The unit has continued to carry out research on English Heritage properties. This year we been part of the multidisciplinary team working on the display of the late eighteenth-century dairy complex at Kenwood House. The unit has also undertaken a major research commitment at Bolsover Castle. This year Bolsover has received substantial English Heritage and European funding with over 1 million reserved for the conservation and redisplay of the Little Castle. Our research to date has already discovered early seventeenth-century decorative finishes that have survived later overpainting and established a greater understanding of the architect's original design concept. The unit is formulating a conservation plan for the interior, which will form the basis of the works programme, and will be heavily involved in overseeing the project. At Eltham Palace, the unit is supporting Major Projects in establishing the original Art Deco decorations in the Courtauld wing.
The unit is developing its role as the national lead organisation for architectural paint research standards. In our various forthcoming publications we are highlighting the fact that despite a growth of available funding there is an acute shortage of qualified researchers, as there are no training courses available in this field. In response to this, the unit attempts to provide some limited training. Last year the unit offered an internship to a Dutch student and this autumn we will be joined by a student from Sweden and a researcher from Historic Scotland. This is clearly one of the archaeological disciplines that needs to be developed if we are to realise the full potential of our built heritage.
Archaeometry
Environmental Studies
Technology
Conservation