7000 years of Chinese jade from the collection of Sir Joseph Hotung

Apollo, Nov, 2003 by Carol Michaelson, Margaret Sax

To illustrate the information that can be obtained from objects like those described in this article, we focus on the tool marks found on a flower and cicada ornament, dated to the Ming or the Qing dynasty, which is a mere nine centimetres high (Fig. 12). The overall dimensions of the ornament suggest it was worked from a small slab of jade, about nine millimetres thick. Tool marks relating to the shaping of the undulating surfaces forming the flower and the cicada survive on the highly decorated front and rear faces. The SEM micrograph (Fig. 9)--the scale bars in this and Figs. 10-11 represent 2 mm--is of a mould taken from the surface of the cicada's wing. Our engraving experiments indicated that the fine parallel grooves seen here are typical of those carved using an abrasive slurry with a disc-shaped rotary wheel. An iron or steel wheel was probably mounted on a lathe and rotated by a foot treadle, similar perhaps to the one depicted in a seventeenth century woodblock print, included by Sun and Sun in their translation of T'ien Kung K'ai-Wu. (20) Another SEM micrograph (Fig. 10) shows the incised decoration on the cicada's wing. The curvature of these features, protruding upwards on this mould, indicates they were carved using a very small wheel.

[FIGURES 9-12 OMITTED]

The tool marks moulded from a hole pierced through the cicada's wing (highlighted in Fig. 12) suggest how pierced features on this and other objects, such as the Tang or Liao earrings (Fig. 2), may have been worked. The SEM micrograph (Fig. 11) shows two distinct features which extend through the thickness of the ornament. On the left, the feature has circumferential grooves, demonstrating that it was worked with a solid drill, about one millimetre in diameter. In contrast, the even narrower features on the right are characterised by faint longitudinal grooves, consistent with the use of a saw to enlarge the drilled hole, in the manner of a fretsaw.

Our examination of this ornament and several other jades has provided evidence for the use of rotary tools during the Ming and Qing dynasties. However, different characteristics are present on some of the earlier jades, for example, the plaque of a face veil (Fig. 13), dated to the Eastern Zhou dynasty, 770-475 BC. Moulded details of the stylised dragon incised on the front can be seen in the SEM micrograph (Fig. 14), in which the scale bar represents 5 mm. The characteristics of the tool marks here show that several different hand-held tools were used in the carving. The generally uneven nature of the marks on the plaque contrast with the even working of the flower and cicada ornament.

[FIGURES 13-14 OMITTED]

The present scientific study is beginning to provide evidence for the techniques by which this extraordinarily tough material was painstakingly shaped, carved and polished using abrasive processes to reveal the hidden qualities that were recognised in the raw stone by Bian He.

Despite the fact that the process of producing jades was extremely time-consuming and labour intensive, the many thousands of jade ritual and ornamental objects that have been made by the Chinese amply testify to the great symbolic and material worth this material held and indeed still holds for them.