Ancient Chinese Silk Fabrics

Understanding and quantifying decay processes within silk fabrics is of prime importance for their restoration and conservation. Detailed models of decay require an understanding of the effects of light, humidity and/or microbes. With this aim, scanning microdiffraction has been used to characterize the microstructure of archaeological silk fabrics from the Famen temple, China. The temple is situated 120 km west of the ancient Chinese capital Xi’an, and is one of China’s most important Buddhist sanctuaries. The silk fabrics were once part of a treasure laid down by the T’ang dynasty emperors as a gift to the temple (618-907 AD).

The information provided by “WAXS imaging” on ID13 is very much complimentary to optical microscopy and SEM studies. Whilst these methods can only visualize the surface morphology of materials, “WAXS imaging” provides additional structural information from the entire sample thickness. Meanwhile, its ability to cover extended areas, very much like the other techniques, ensures a statistically significant number of fibers can be sampled.

The optical microscopy images on the right show a modern plain-weave silk fabric (top left), and three archeological plain-weave silk fabrics from the Famensi site in varying states of decay.

From the silk fabric's diffraction pattern, the azimuthal width of the 210 reflection turns out to be a sensitive indicator of decay state. The histogram of azimuthal width distribution is found to be symmetric for a modern silk thread and asymmetric for the fabrics, which can be attributed to misorientation of both the nanofibrils and fibres. Analysis of azimuthal broadening suggests that fabric decay is related to a loss of the connecting amorphous network within individual fibres. This process is a precursor for cleavage within the nanofibrils, allowing the silk fibres to break up small fragments.

Composite scanning diffractometry images based upon the integrated intensity of the 210 reflection showing the two main fibre-orientations within the fabrics. Empty spaces are indicated by lighter regions.

The results from this work suggest that silk fabric conservation should be aimed at keeping the nanofibrillar morphology intact. One possibility is to use an artificial polymer matrix to embed the fragile nanofibrils.

Characterizing the decay of ancient chinese silk fabrics by microbeam synchrotron radiation diffraction
Hermes A.C., Davies R.J., Greiff S., Kutzke H., Lahlil S., Wyeth P., Riekel C.
Biomacromolecules 7, 777-783 (2006)