Spectroscopic Analysis of Colorants Used for bachiru Carving Technique Found in the Shosoin Treasures

ABSTRACT

The Shosoin treasures, which include the belongings of Emperor Shomu (CE 701–756) and Empress Komyo (CE 701–760), have an honorable origin and have been continuously handed down for generations since the eighth century in the Todaiji temple in Nara, Japan. Some of the beautiful artifacts found among the treasures display the bachiru carving technique, in which a delicate pattern is produced by carving dyed ivory or antler using additional painting. To elucidate the colorants used for dyeing and painting in the bachiru technique, non-invasive scientific analyses using fiber optic reflectance spectrometry in the visible region, X-ray fluorescence spectroscopy, and X-ray diffraction were performed for eight treasures: a go game board, two go pieces, a nyoi (ritual nail pole), a kugo harp, a bird-shaped accessory, a kaburaya arrow, and a ritual ruler. Second derivatization of the reflectance spectra led to characterization of the dyes in the treasures as sappanwood, lac, madder, gromwell, and indigo. Lac and atacamite were respectively identified in the red and green areas of the painting by reflectance spectrometry and X-ray diffractometry. These results indicated the use of a variety of colorants for the bachiru carving technique in the eighth century.

KEYWORDS:

• Shosoin treasure
• dye
• bachiru carving
• sappanwood
• lac
• akane madder
• gromwell
• indigo
• fiber optic reflectance spectrometry
• X-ray diffraction analysis

Disclosure statement

No potential conflict of interest was reported by the authors.