More Reliable Dating of Japanese Silk Mounting Textiles for Conservation Decisions: Effects of Silk Processing on Silk Surface Morphology and Aspartic Acid Racemization

Abstract

ABSTRACT Dating silk mounting textiles is important for understanding their condition and susceptibility to degradation. Amino acid racemization is a technique currently used for this purpose. The research presented here aimed to clarify when this technique is reliable and when it is not. Silk fibers taken from a cocoon and from Japanese mounting textiles were studied using optical microscopy to document surface roughness. Chiral capillary electrophoresis mass spectrometry for amino acid racemization dating (AAR), liquid chromatography mass spectrometry for dye analysis, and FTIR for analysis of sericin and other materials adhering to the silk were also used. A change from rough fiber surfaces (greater than a hundred years old) to smooth fiber surfaces (less than a hundred years) was found. This correlated with the time of the introduction of Western degumming methods in Japan. Synthetic dyes were not found on the earlier silk fibers with rough surfaces. AAR dating measurements on rough surfaced fibers with remaining sericin correlated better with the estimated age of the silk fabrics than fibers with smooth surfaces, suggesting the technique should only be used for silk fibers with rough surfaces. A screening method for fibers for AAR analysis was outlined.