TOWARDS A ROUTINE METHODOLOGY FOR ASSESSING THE CONDITION OF HISTORIC SILK

To ensure continued access and long-term preser vation itis essential to understand the condition of an artefact, andthe behaviour of its component materials, in order to setlimits on display and handling. In support of curators andconservators of collections with historic textiles, we aredeveloping rapid and routine technology, involving nearinfrared spectroscopy coupled with multivariate analysis,which, when applied non-invasively on-site, will allow theestimation of the state of deterioration of silk fabrics.Pursuing this aim, we have now carried out further analyticalstudies on silks artificially aged under different regimesfor up to 20 days: dry thermal, high heat and humidity, andsunlight equivalent irradiation. The tensile strengths, yellownessindices, apparent molecular weights of fibroin, andnear infrared spectral sorbed moisture parameters for theaged silks were determined. The mechanical performanceof silk diminished exponentially over each ageing timecourse. For the various silks, the increases in yellownessindices and decreases in fibroin molecular weights andmoisture contents showed similar kinetics to the mechanicalchanges. While each parameter was correlated with thetensile strength, silks exposed to the different acceleratedageing factors exhibited diverse correlations. It is concludedthat, when formulating a general model for characterisingthe condition of silk using chemometrics, the referenceset should include examples of silks which have beenexposed to the full variety of ageing factors.