Analysis of Degraded State of Excavated Archaeological Silk Fibers using FT-IR Microscopy

Abstract

Excavated organic materials such as textile fabrics are usually heavily degraded and hence their scientific identification is rather difficult. The authors are continuing the analysis of degraded natural textile fibers using FT-IR microscopy to clarify their general characteristics at molecular level. In this report, the infrared spectra of silk fibers found at the Fujinoki tumulus were analyzed in detail. The most remarkable change of spectral patterns in degraded silk fibers compared with those of modern silk fibers was the broad superposed appearance of amide I and II absorption peaks. As a result of the investigation of the secondary structure of fibroin molecules, the main reason for the spectral deformation was found to be the increase in crystallinity associated with degradations.
In this research, the FT-IR microscope at JASRI was used. It requires only very minute samples due to the bright IR light source using synchrotron radiation. This makes it convenient for the study of cultural properties.
The identification of silk fibers in degraded state undoubtedly contributes to the understanding of historical features of the remains at a particular tumulus.