Structure and stable isotope ratios of ancient and artificially aged silk fabrics

Understanding the degradation of silk fibers and tracing silk fabrics from archeological sites have always been challenging. The stable isotope technique provides the possibility to trace ancient textiles, especially for the controversial issue of the silk origin. Chinese historic silk fabrics from the Xia dynasty (about 4000 years ago), Warring States period (B.C. 475- B.C. 221), Tang dynasty (A.D. 618- A.D. 907), Southern Song period (A.D. 1127A.D. 1279), Ming dynasty (A.D. 1368- A.D.1644), and Qing dynasty (A.D. 1636- A.D. 1912) as well as some artificially aged silk specimens have been examined by scanning electron microscopy (SEM), attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy, and isotope ratio mass spectrometry (IRMS) to investigate their degradation for traceability and preservation. It has been found that the surface morphology and secondary structure of silk were destroyed in the degradation process. Under most aging modes, the silk fabrics were enriched with heavy stable isotopes after degradation. In the case of charring, the isotopic ratios of heavy hydrogen and oxygen isotopes showed different variation tendencies, which need to be further studied for better understanding. The results revealed that stable isotope ratios of silk fabrics are affected by different aging conditions. The degradation of silk fabrics is an important cause of stable isotope offset in historical silk fabrics. Overall, this study provides useful insights into the silk degradation mechanism and can serve as a useful reference for tracing the rich textile heritage.