Heat and moisture promoted deterioration of raw silk estimated by amino acid analysis

Silks are amongst the most precious artifacts of our textile heritage. While most silk fabrics are made from degummed silk, some in collections, such as ancient Chinese Juan, are composed of raw or just partially degummed silk. Such silks with remnant sericin gum may require special consideration for their optimum preservation. Conservators and curators then need to know which of the silks in their collections are in this category, and what effect the sericin has on the ageing of silk fibres. In the study reported here, the artificial heat and moisture ageing of raw silk was investigated by means of amino acid analysis. Amongst various amino acid molar ratios, Asp/Gly proved a valuable indicator of residual sericin gum on aged silk. Measurement of the tyrosine content was also useful for gauging the conservation state of silk in some circumstances. The results of the amino acid analyses when combined with those for tensile tests suggested that sericin did not inhibit fibroin deterioration under the ageing conditions employed.