Heritage conservation

Parchment

Hydration and relative humidity has a significant effect on the molecular and mesoscopic structure of parchment, with the surface-ink interface often undergoing degradation as a result of environmental damage ^[4,5]. Analysis of such ink-surface interactions on parchment using micro-focused X-ray spectroscopies to probe the upper few microns of the surface where writing is found will allow local changes at the surface of parchment to be probed shedding light on the mechanism of this important degradation process ^[6]. Given this information, new protocols for archive record maintenance, storage and novel cleaning techniques can be established.

Ivory

A pressing current challenge in conservation, archaeology, anthropology and art history is the fully-integrated study and management of artefacts made from animal tissues such as ivory. These materials are inherently complex and the authenticity and origin of the source of the material is often problematic and requires a non-destructive approach to more accurately catalogue the materials according to their elemental composition. It is essential that our ability to determine the origins, authenticity and date of ivory objects and working residues is substantially enhanced. μ-XRF and XAS analysis will a powerful method to map the elemental compositions and local structures of ivory-based materials.

Metallic and wooden artefacts

Many metallic artefacts are found to decay post-excavation, which is related to the presence of Chlorine. The processes by which corrosion phases form, and later evolve, strongly influence the conservation and restoration of these metal artefacts. The microscale variations of iron and chlorine speciation along the depth of the corrosion crust could be determined using μ-XAS. Furthermore environmental XPS would allow a greater understanding of the surface chemistry and dynamics of the initial stages of the decay process. Distribution of metals in composite materials can be probed by μ-XRF, μ-XAS. e.g. swords comprised of Fe, As, Ni composites, or Fe and Cu in Egyptian bronzes where changes in oxidation state can be observed by deterioration.

Synchrotron studies at also revealed the origins of decay in timber frame of the salvaged Tudor warship The Mary Rose. Sulphuric acid formation, identified deep within the timbers, was observed to react with the timber surface leading to its decay. Unfortunately existing preservation methods are unable to prevent the acid formation, however, having identified the problem, new preservation methods can be sought to prevent the formation of sulphuric acid and retard the decay within the timbers and so save the historic remains of this ship.

Masonry and sculptures

An understanding of how to combat pollution induced weathering of masonry from historic buildings and sculptures,such as York Minster ^[7] requires access to XAS facilities capable of measuring light elements (e.g. C, S, Mg, Al, Ca) and is ideally suited for the soft x-ray specification of the proposed VERSOX beamline. Imaging of light elements will prove valuable for mapping local regions of decay and elemental distribution within masonry samples and identifying the local structure of amorphous salts. XPS will permit the interaction of atmospheric gases with historic masonry to be examined to aid our understanding of the influence of hydration (relative humidity) upon salt formation. In addition the effect of organic acids with surfaces of building materials can also be investigated to assess the effect of modern day pollutants on historic buildings.

Glass

The effect of weathering on medieval stained glasses can result in changes in glass colour, as well as the formation of surface weathered phases. The combination of μXRF and μXAS information contributes to our understanding of the way chemical phases react as a function of the long-term weathering, but also to the conservation of these stained glasses ^[8,9].

Photographs

An improved understanding of the effects of micro- and macro-environmental conditions on the degradation of colour photographic media is essential for the preservation and management of colour photograph collections for future generations ^[10,11]. Artificial ageing methods are being employed to follow the aging of colour photographs under different environments. Analysis of the resulting changes requires by an array of spectroscopic techniques to map out the changes as the photographic dyes degrade. By constructing a model of the environmental effects on the stability of colour photographs using such non-invasive measurements will allow the life expectancy of colour photographs from The National Archives to be estimated.

Polymers and plastics

Heat-set tissues were once applied to paper as a remedial conservation treatment. The nature of the substrate and adhesive, combined with the application of heat, can be detrimental to the long-term stability of laminated documents. The issues surrounding the identification and deterioration of synthetic polymers are of growing concern within the heritage sector. They pose significant stabilisation problems because of the processing methods, additives and treatments used. The routes of degradation are often complex, requiring an intimate knowledge of the interfacial chemistry between the paper and laminate in order to develop conservation and preservation protocols.