EMF - Abstracts

Analysis of Silk Deterioration for Informed Conservation.

Paul Garside and Paul Wyeth (Southampton University)

The ability to identify fibres in historic textiles and to characterise their state of degradation is essential when considering potential conservation treatments. Silk fibres, found in many important artefacts, are particularly susceptible to deterioration and so are a special area of concern. From the middle ages, silk processing, and especially the use of metal salt weighting agents, lead to catastrophic damage.

Silk deterioration is generally assumed to proceed from the accessible, amorphous regions of the fibroin aggregates, in which the metal salts are believed to accumulate. Our research has concentrated on developing a micro-methodology to assess the ageing of these materials, and specifically to identify spectroscopic signatures that correlate to compromised physical properties.

To monitor the process of degradation, samples of habutae silk were weighted using various historic methods and subsequently subjected to accelerated ageing, either by exposure to elevated temperatures or high intensity illumination. Physical parameters of the materials were then determined, including the breaking strength and viscoelastic properties. The samples were subsequently investigated by polarised-ATR-FTIR spectroscopy, HPLC, thermogravimmetric analysis and SEM-EDS examination.

Polarised-ATR spectroscopy allowed the degree of crystallinity and orientational order of the material to be assessed. The ATR spectra of silk fibres showed marked changes as they were turned with respect to the polariser, reflecting ordered crystallinity but disruption of this layered, -pleated sheet arrangement with ageing. The correlation of these results with the mechanical properties of the silks, and the impact on choice of conservation treatment, will be discussed.