Wood identification of a wooden mask using synchrotron X-ray microtomography

Recently, an old wooden mask was discovered at Yatsushiro city, Kumamoto Prefecture, Japan. This mask has been handed down from the end of the 16th century; a Japanese man of arms brought it from the Korean Peninsula during the war between Japan and Korea. In the Korean Peninsula, Hahoe masks have been stored in the Hahoe village and were designated as national treasures in 1964 and are presently possessed by the National Central Museum. Some concerns existed that this wooden mask could be one of the Hahoe masks. Since the Hahoe masks in Korea have all been made of alders (Alnus spp.), wood identification became a key issue to answer the abovementioned concerns. In fact, a flaked sample fragment was available and it was small and brittle enough to be sectioned without embedding. Furthermore, the sample was compressed in the tangential direction so that the surface was not clear enough to be explored by a scanning electron microscope. In this study therefore, a synchrotron X-ray microtomography at SPring-8 was used for the first time for wood identification. The experimental setup of BL20XU at SPring-8 allowed us to image any wood sample at a special resolution of 0.5 μm, which is enough to explore most anatomical features for wood identification established using optical microscopy. The sample was clearly diffuse-porous hardwood characterized by uniseriate heterogeneous ray and simple perforation. As a result, the mask turned out to be made of Salix sp., and the possibility that it is one of the Hahoe masks was ruled out.