For three years between 2013 and 2015 the Office of the Shōsōin conducted research on bast fiber items among the Shōsōin treasures. The research was led by Katsuhiko Masuda along with Nobuko Hiroi, Fumio Okada, and Masaaki Ariyoshi. They investigated the items by inspection with the naked eye, recording with a high definition digital camera, and examination through a microscope. In determining the materials, they used optical microscopy to analyze the longitudinal and the crosssectional characteristics of the fibers, as well as using the Graff C staining test for the absorption of C color dye (JIS standard) to determine the type. Due to the age of the fibers, some did not necessarily correspond to the standard form and color absorbency. In those cases, opinion as to material type was sometimes divided. The content of this research is published in the Shōsōin Bulletin no. 40 and is accessible on the Shōsōin home page as a pdf file. I will introduce one part of the research.
The treasures that were investigated included bags, furnishings, musical instruments, garments, and military equipment. All these treasures used bast fibers as a part or as a core invisible from the outside. In addition, several complete bolts of woven bast fiber cloth have been preserved. In the Nara period, bast fiber cloth was paid as tax to the central government, and was valued as currency. The measurements were determined: the chō cloth調布, paid as a tax in kind, was set at a length of 4 jō 2 shaku (approximately 1247 cm) and a width of 2 shaku 4 sun (approximately 71 cm). Yō cloth 庸布, paid as a converted labor tax, was set at 2 jō 8 shaku (approximately 832 cm) long and 2 shaku 4 sun (approximately 71 cm) wide. Fabrics bearing written inscriptions indicating they were chō or yō tax cloths were produced in Japan, and almost all were either hemp (taima ) or ramie (chōma ). There are also examples of bast fiber items brought from the Asian continent. A hemp cord binds copper spoons thought to be products from Shilla on the Korean peninsula. The bast-fiber label sewn onto the corner of an imported felt rug is ramie. On the other hand, the possibility was indicated that the bast-fiber core (interfacing) for embroidered shoes thought to be of Tang Chinese
production used jute (ōma), which does not grow in Japan.
Japan has a history of lumping together plants from which one can extract the fibers under the generic term asa. For that reason, in Japanese the noun asa is ambiguous, covering an extremely broad range of materials. One conjecture, surmises that in the Nara period the workers who used asa cloth and cords, might not have paid much attention to the distinction between ramie and hemp, and indeed as cloth or cord ramie and hemp are difficult to distinguish with the naked eye. For instance, results of the investigation of materials showed that three bags of the same shape and size used for storing folding screens mixed ramie bags and hemp bags together. One does not sense a need to be consistent in use of materials, even when items were used for the same purpose.
By sharing this information with people from Korea, China and other countries we invite further collaborative research.