Leather material found on a 6th B.C. Chinese bronze sword: a technical study

Area of Science:

• Archaeological Science
• Materials Science
• Ancient Technology

Background:

• An archaeological excavation in Yun country, Hubei province, China, uncovered leather remnants on a 6th century B.C. bronze sword.
• The leather fragments were covered with red pigment, prompting an investigation into their manufacturing technology.

Observation:

• Raman spectroscopy identified the red pigment as cinnabar (HgS).
• Fourier-transform infrared (FT-IR) and X-ray fluorescence (XRF) analyses revealed elevated levels of calcium (as CaCO3) and iron (as Fe2O3) in the leather compared to surrounding soil.
• These elemental compositions suggest specific processing methods were employed.

Findings:

• The analytical results indicate the use of lime for depilation and retting processes.
• Evidence points to the application of an iron-aluminum (Fe-Al) compound salt as a tanning agent.
• The identified techniques suggest a sophisticated understanding of leather preservation.

Implications:

• The findings suggest that the Fe-Al salt tanning technique was developed during China's middle and late Spring and Autumn Period.
• This research provides crucial insights into the advanced ancient Chinese leather industry.
• The study highlights the effectiveness of combined spectroscopic and elemental analysis in uncovering historical material technologies.