In-situ investigation of inner structure of Kongo Rikishi statues at Oiwayama Bishamonten
The Oiwayama Bishamonten in Ashikaga city, Tochigi prefecture is said to be one of the three major bishamontens in Japan in addition to those at Kurama-yama in Kyoto and at Shigi-san in Nara. Wooden Kongo Rikishi statues, which are cultural properties designated by Ashikaga city, are enshrined at Sanmon gate. According to recent research, there are concerns about the deterioration of these properties over time. In particular, the inclination of the head of Agyo statue has been pointed out. Considering this situation, the owner plans to embark on a restoration project.
To carry out the project, it is necessary to clarify the inner structure of the statues, especially how the parts are connected to each other. However, an in-situ and non-invasive investigation is required without transferring statues, which are about 2.8 meters tall, from Sanmon gate. At the request of the owner via Ashikaga city, Masahide INUZUKA conducted an investigation into the inner structure of the statues using X-ray radiography from September 9th to 10th, 2020.
As shown in the photograph, the X-ray was irradiated on Kongo Rikishi statues from an X-ray tube set on the scaffold assembled in front of the statues. Before conducting the investigation, important discussions were done to determine how imaging plates (IPs) should be set in the limited space behind the statues. For this research, we used the developing equipment, which is dedicated to IPs, and proceeded with the research by confirming the X-ray transmission images each time they were obtained.
From the X-ray transmission images obtained during the above research, the inner structure of the statues and the information about positions and numbers of nails used in past restoration works were revealed. Such information will be referred to during the restoration works in the future.