Conservation and computational imaging technologies

Silver roman imperatorial denarius of Julius Caesar, CAESAR /Aeneas advancing to front, holding Palladium in palm of right hand and carrying father Anchises on left shoulder (O 19 mm), Archaeological Museum of Amphipolis, clockwise from top left: digital image, comparison between PTM (top) and a standard computer graphic approximation (below), normal map and RTI visualization in specular enhancement rendering mode (c) Eleni Kotoula
Silver roman imperatorial denarius of Julius Caesar, CAESAR /Aeneas advancing to front, holding Palladium in palm of right hand and carrying father Anchises on left shoulder (O 19 mm), Archaeological Museum of Amphipolis, clockwise from top left: digital image, comparison between PTM (top) and a standard computer graphic approximation (below), normal map and RTI visualization in specular enhancement rendering mode (c) Eleni Kotoula

I’m Eleni Kotoula, a PhD student in the Archaeological Computing Research Group, University of Southampton.  I am a conservator of antiquities and works of art and I have worked in practical conservation since 2004 in museums and cultural organizations in Greece. My conservation research is focused on non-destructive analysis of archaeological material and accelerating ageing of adhesives/ consolidants used in conservation.

I hope you agree that many interesting finds, covering a variety of materials and artefacts types have been presented so far in the course. In Week Five processing (Processing the finds) and registering of finds (Registering the finds) are discussed. What’s next? Conservation!  But what is conservation? How does computational imaging assists study and conservation of finds?

The conservation of antiquities lies on the edges of the double function of artefacts as resources for archaeological and historical information and as displayable objects, while it attempts to pace the rate of the processes of decay, minimise the deterioration effects and prevent alterations and damage. The cornerstone of conservation is the requirement for long term preservation, balanced with the needs to investigate and interpret, access, use, display and reveal objects and their values.

Undoubtedly visual analysis is a milestone in conservation practice which seeks to provide data relevant to structure, manufacture, damage and use of the object as well as materials identification. All surviving evidence is examined in order to lead to conclusions regarding characterization of the object and its condition. The findings of the visual analysis determine the goal of treatment and treatment type (conservation decision making). The changes introduced during treatment, after discovery, and throughout the artefact’s museum life, not only in appearance (including geometry, colour and texture), but also in chemical structure, are among the most influential processes that determine the artefact’s future, and dramatically affect its interpretation. Remedial treatment has a direct influence on chemical and physical properties of the objects, while preventive conservation or environmental preservation activities affect the object indirectly, as they can change its condition by altering its environment.

Application of digital recording methodologies help conservators perform visual analysis, document and monitor the condition of artefacts and the conservation operations. A characteristic example is the application of RTI in ancient Greek and Roman coins before, during and after cleaning. Also, the integration of imaging techniques offers advanced alternatives to traditional conservation methodologies. Considering the objectives of a conservation project RTI and photogrammetry can contribute significantly in: prevention, investigation, examination and analysis, documentation, communication, dissemination and presentation.

RTI helps exploration of artefacts’ biographies by enabling advanced examination of manufacture and use evidence, decay and conservation operations. Integration of microscopy and RTI makes it possible to catalogue the shape and topography of the various components of artefacts at a microscopic scale. Moreover, the synergy of infrared imaging and RTI highlights the texture and three dimensionality features of the inner layer in case of painted surfaces and assisted the examination of documentary artefacts. In the case of translucent materials the transmitted RTI method is a useful complementary technique. Photogrammetry (as you have learned on the course in Photogrammetry and laser scanning of artefacts) can also be used for 3d digitisation, enabling virtual examination of finds and offering possibilities for virtual reconstruction of incomplete finds. Similarly to RTI, the integration of photogrammetry, multispectral imaging and microscopy provides useful information and enable the user to examine these features in 3d space.

For an introduction to conservation I propose The elements of archaeological conservation by Cronyn, J. M., & Robinson, W. S. published by Routledge. For an intoduction to conservation Imaging  you can have a look at The AIC Guide to Digital Photography and Conservation Documentation edited by J. Warda published by the American Institute for Conservation.

Open access resources for conservation
1. Canadian Conservation Institute
2. Institute of Conservation
3. The Getty Conservation Institute
4. Posts on the ACRG site about RTI 
5. We work very closely with Cultural Heritage Imaging who have many resources on RTI.

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