Discovery of Beeswax as binding agent on a 6th-century BC Chinese Turquoise-inlaid Bronze sword

Recent archaeological field surveys and excavations at Qiaojiayuan, a platform 40 km west of the Yun County in present-day northwestern Hubei Province (central China), revealed four tombs (M3, M4, M5 and M6) dating back to around 6th to 5th century BC. The grave's layout, artifact assemblages and burial practice indicate that the owners of these four graves were aristocrats of the Chu state. Five turquoise-inlaid bronze artifacts (two swords and three dagger-axes) were excavated. The sword from M4, imbedded with pieces of well-cut and finely-polished turquoise on its handle, was in a very bad state of preservation and underwent conservation treatment. Some sticky, whitish pastes were exposed when the inlaid turquoises dropped off. The pastes were supposed to be residues of unknown binding agents. Samples of the pastes were collected for FTIR (Fourier Transform Infrared Spectroscopy) and XRD (X-Ray Diffraction) analyses to determine the chemical component(s). The results revealed that the pastes were composed of almost pure beeswax. This indicated that beeswax was used as binding agent in turquoise-inlaid bronzes as early as the 6th to 5th century BC in China. Review of recent technical studies suggested that beeswax was used in early China in several different regions (mostly southern part of China) for at least two different purposes (binding agent and lightening).

► Five 6th-century BC turquoise-inlaid bronzes were recently excavated in central China.
► We identified some whitish pastes on a turquoise-inlaid sword using FTIR and XRD.
► Beeswax was suggested to be used as binding agent in early China inlay technique.
► Beeswax in other regions may also be used for lightening in early China.
► This research will promote our understanding of how ancient Chinese exploited natural resins to meet technological change.