Towards on-site collections management: NIR characterisation and condition monitoring of textiles

Figure 1. In situ analysis of an early 19th Century shoe (Photography by Mike Halliwell, Textile Conservation Centre). (click image for larger version)

The ability to characterise and monitor the condition of artefacts on site should enable better informed collections management, such as improved storage, handling strategies and gallery rotations. Assessment requires minimum disturbance to objects, avoiding loss of key information, and integrity, whilst gaining maximum information. It is for this reason that I am presently investigating the application of Near-Infrared Spectroscopy (NIR) as a non-invasive, portable method of analysis for synthetic textile artefacts. This technique has already being successfully applied in situ within the food industry and agriculture, for example, and its possibilities for on site application within museums will form the major part of my Arts and Humanities Research Council funded PhD research.

Near Infrared Spectroscopy, as the name suggests, is concerned with the application of near infrared radiation (780-2500nm). NIR spectra are produced by the absorption of radiation at shorter wavelengths than that found in more conventional mid infrared spectroscopy. Due to the high energies involved the spectra are dominated by high frequency vibrations, primarily relating to hydrogen containing bonds, in particular C-H, N-H and O-H. Therefore organic materials are particularly suited to investigation. One key advantage of NIR is its non-contact application via a remote, flexible probe, removing the need for sampling (Figure 1). The ability to examine the entire surface of an object will ensure that the data are representative of the whole, rather than limited to areas of minimum disturbance. In addition, NIR can readily sample to depths of 1mm or more, allowing successful analysis of textile layers and interlinings and removing the need for intervention.

During the initial stages of my work, I will be compiling a spectral database of man-made and synthetic reference material, distinguishing between polymer classes and sub-classes. Subsequently, this will then be used to enable fast, reliable identification of textile material held within the Museum and other heritage collections. As with most collections, textiles are often complex in nature, so where possible I intend to take into account factors such as polymer blends, surface coatings, additives and age. These are bound to influence the results, so processing information will be required from manufacturers and suppliers, supplementing the data contained in the reference database and assisting in the interpretation of the spectra.

The later stages of my work will entail the application of NIR to identify markers of degradation within particular synthetic textile materials. I expect to define the precise area of study during my initial spectral survey. I am already in close dialogue with the Museum's Contemporary Textiles Department, to identify areas of the collection that would benefit from continuous condition monitoring. Suggestions to date have included de-lamination of coated textiles and the deterioration of synthetic painted textiles.  

Acknowledgements

I am grateful for the ongoing support of Professor Graham Martin at the V&A and Dr Paul Wyeth and Dr Paul Garside at the Textile Conservation Centre, University of Southampton. Nell Hoare, Director, Textile Conservation Centre, was kind enough to give permission for the inclusion of the action shot.  http://www.wsa.soton.ac.uk/conservation-and-museums/