The inaugural meeting of the infrared users group

Philadelphia Museum of Art, March 1994

The inaugural meeting of the Infrared Users Group (IRUG) for the Analysis of Artistic and Historic Materials was held at the Philadelphia Museum of Art on the 24 and 25 March this year. The meeting was organised by Michele Derrick (Getty Conservation Institute) and Beth Price Philadelphia Museum of Art). It follows on from Michele's earlier work in compiling an Infrared Spectral Library of Artist and Artisan Materials,' currently with contributions from over 12 laboratories chiefly in the US.

The meeting was organised with the aim of sharing expertise in various infrared techniques and also to further the collection of reference spectra for the library. Each of the two days had a morning session of presentations followed by a demonstration of techniques and their uses in the afternoon.

The V&A's Conservation Department has a long history of sharing expertise and knowledge. The Science Group have developed expertise in the measurement of spectra directly from samples taken by abrasion using silicon carbide paper. Although not widely used in the conservation field, the technique provides rapid sampling for characterisation of organic materials on surfaces.

The technique was first suggested by Spragg2 in 1984. Graham Martin first suggested its use for the examination of organic compounds in museum artefacts. Gretchen Shearer (at the time studying for her PhD3 at the Institute of Archaeology in collaboration with the V&A) took up the suggestion and compiled a library of reference spectra of materials commonly found in museum artefacts using the technique. Although we have made the library available to interested parties on an individual basis, it has always been the intention to share the information on a wider scale.

The proximity of Easter meant that the air fares to the USA were monstrously expensive. I was therefore fortunate to be able to attend the meeting, not only to represent the V&A but also, as it happened, as the only European! I gave a short talk on the development of the silicon carbide sampling technique and its applicability to conservation. I was also able to show its use in practice.

In all, 15 presentations were given by representatives from conservation, forensic science, academic institutions and manufacturers of infrared equipment. The presentations covered a variety of topics, including specialist sampling and measuring techniques, details of developments in instrumentation and accessories, and future developments for increasing the spatial resolution of spectroscopic measurement beyond the diffraction limits (occurring for samples smaller than 10 gm) by using mathematical manipulation and masking techniques.

The meeting ended with an open discussion on the future of the group and the collection of reference spectra for the 'Artist and Artisan Materials: Infrared Spectral Library'. Appropriate spectral manipulations and formats for data transfer for spectra for the library were also discussed.

For the library to be a useful a reference source, spectra would need to be checked and edited as necessary. As this greatly increases the work involved in compiling the library, spectra will be divided into groups according to material and/or specialist techniques. Volunteers were chosen to look after particular parts of the library, the V&A taking over the responsibility for diffuse reflectance spectra. Further, it was agreed that the library would be made available through Internet, thereby avoiding the administration involved with repeatedly sending out disks of the digital information.

A resounding chant of 'good spectroscopy first' came from all participants. Data contained in the library should, therefore, as far as possible be raw data; no smoothing or baseline correction should be applied.

The library will be very useful for conservation as it contains spectra of aged, degraded materials as encountered on many artefacts. Distribution will be free but limited to individuals and organisations who have contributed to it. In this way the group hopes to expand further on the benefits of such large scale co-operation. The group will meet every one or two years with the V&A suggested as host for one of the future meetings.

References

1. Derrick, M. et al in 'Preprints, ICOM-C C 10th Triennial Meeting, Washington, US, August 1993, Poster Session Abstracts.'
2. Spragg, R.A. 'A rapid sample preparation technique for diffuse reflectance measurements'. Applied Spectroscopy 38, 1984, pp.604-605.
3. Shearer, G.L., 'An evaluation of Fourrier Transform Infrared Spectroscopy for the Characterisation of Organic Compounds in Art and Archaeology', PhD Thesis submitted to Department of Conservation and Materials Science, Institute of Archaeology, University College, London, 1989.