A COMPARATIVE ANALYSIS OF DEGRADATION IN NATURALLY AGED AND EXPERIMENTALLY DEGRADED SILK (TEXTILE CONSERVATION, AMINO ACID, HISTORIC)

In order to develop effective methods for preserving historic silk, it is necessary to determine why some silk fabrics deteriorate while others endure. This research characterized the physical and chemical degradation that has occurred in naturally aged silk, and studied variables and conditions known to degrade silk.; Fifty four undyed, historic silks (10 to 400 years of age) were analyzed and the physical morphology and chemical composition compared to that of new silk to determine the extent of degradation. New silk was subjected to 12 chemical, heat, and light treatments that simulated manufacture, care, and use, and damage was assessed. Cocoon silks (new, 15-20 and 40 years old) were analyzed to determine degradation resulting from natural conditions. Evaluation methods included breaking strength tests, dilute solution viscometry, amino acid analysis, microscopy, photoacoustical infrared spectrophotometry, and neutron activation analysis.; Among the historic silk fabrics, significant differences (p < .05) in tenacity were found between weighted and unweighted fabrics and among different age groups. Strength losses increased with greater age. Significant decreases in viscosity were related to increasing age. Experimental treatments caused significant tenacity losses. Xenon light exposure and NaOH produced strength losses of 20% or greater and significant decreases in elongation. Boiling water, NaOH, and xenon light treatments caused significant decreases in viscosity. Amino acid analysis suggested that experimental treatments attacked amorphous regions of fibroin, producing significant losses of long side-chain amino acid residues. Significant increases of glycine, alanine, and serine; significant decreases of seven amino acids; and significant increases in NH(,3) resulted from light degradation. Photoacoustical infrared subtraction analysis showed different modes of degradation in fibroin by acid, alkali, and light.; Viscosity differences between new and 15-20 year old and new and 40 year old cocoons were highly significant (p < 0.003 and p < 0.001). No significant amino acid differences were found among cocoon silks age groups.; This research suggests that silk degradation may be initiated by manufacturing processes and exacerbated by light and oxidation over time. The importance of protecting silk from light exposure is emphasized.