A Little More Reflection, a Little More Depth: Applications of Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) in Heritage Textile Conservation

Diffuse reflectance infrared spectroscopy (DRIFTS) overcomes the limitations in attenuated total reflectance Fourier transform IR (ATR FTIR) analysis of low beam penetration into materials, and reduced signal from scattered specular reflectance for thin layers on uneven surfaces. Using a handheld 4100 ExoScan FTIR spectrometer with a diffuse reflectance sample interface, in-situ non-invasive micro-analysis was successful in three fibre residue and fibre degradation studies: 1. Evaluating the non-ionic detergent Dehypon LS54 for wet cleaning. Dehypon LS54 is a new commercial detergent available for textile conservation. DRIFTS was used to assess its removal from fibres in the cleaning process. Detergent traces in washed but unrinsed fabrics showed characteristic spectral peaks. ATR FTIR could not detect any detergent. 2. Identification of oils characterising historical Turkey red (TR) calico dyeing. DRIFTS revealed traces of oils on calico fabric for historical TR manufactured in mid-19th century. Distinctive spectral absorbances for oil bonded to fibres were detected in known TR textiles. These were absent in un-oiled calico and textiles that looked like TR but not made by the process. Thus DRIFTS offers a quick, non-invasive analytical screening tool to identify historical TR textiles. 3.Degradation assessment for historical viscose rayon fibres. Viscose rayon is weak when wet - an issue for textile conservation. Its strength reflects excess hydroxyl groups, amorphous polymeric structure, and low degree of polymerisation, and is affected by manufacturing methods and ageing. DRIFTS enabled historical rayon yarns to be grouped as low, moderate and extensive degradation from spectral information of hydroxyl groups, and peak sizes and shapes