X線透視による金色堂の研究

抄録

Preceding the restoration work expected to be made at an early date, an x ray radiographical survey was carried out on the wooden materials of the konjikido building, the Chuson-ji Temple at Hiraizumi. The hardness of x ray used is of the order of 50kv, which is determined by the preliminary test to be most appropriate for the study of wooden member of thickness up to 50〜60cm. The bracket on each column in this building is piled up with wooden tenons only, instead of using a metal core. Contradicting with the traditional opinion that the four decorated columns of the central altar are hollow, the radiography revealed their structure as follows. In each column, eight pieces of board are fixed with iron nails to an octagonal core lumber to make a round piller, and the applied cover boards have been almost decayed by bacteria. Every one of those columns and also of other timbers of this building is covered with Japanese lacquer layer for the purpose of decoration. This lacquer layer seems to prevent aspiration of moisture of wood, and to make a favorable condition for propagation of the bacteria in the wood in summer time. The decay of the cover boards may be understood to have been the result of this effect. The core lumbers, however, to be almost free from decay. The narrow gap between the core and the applied cover boards, existence of which is easily seen on the radiographs, is thought to be responsible for losing the moldering consition thus invoked in the column. The presence of the lacquer layer, on the contrary, seems to have prevented invasion of insects from the surface. Insect damages can be seen at some of combined portions of part materials. But such damages seem to be rather smaller compared with the decay from fungi.