Type of Research Fundamental Research
Research Title Research on Wood Members of Historical Building Based on Wood Science
Head of the Research Team Prof. SAKAMOTO Minoru
Research Period FY2016-2018
Purpose This research takes a scientific approach to the analysis of old wood members used for historical buildings from the ancient to the early modern period stored by the National Museum of Japanese History to make it available as a research source. The results are used to track the aging process of wood, reconstruct the paleoclimate, and develop a calibration curve for radiocarbon dating in Japanese Archipelago.
Result The wood members of a historical building stored in the Rekihaku, presumed to be those of the Hōryuji Temple, are one of the best known and best preserved collections of wood members in Japan. The researchers re-evaluated wood members of  historical building as source materials. The wood members were taken out one by one in the storage room for comparative studies, referring to the investigation records by Professor Emeritus Hamashima and the repair records. The studies included: measuring; observation of shapes and processing traces; visual inspection of tree species, number of annual rings, conversion of timbers; and identification of the building in which the members were used. The cooperation of graduate and undergraduate students majoring architectural history was requested. In order to determine the age of tree rings, a high-definition digital camera was used and broken pieces which fell off from the members were collected for radiocarbon dating. Identification of all of the wood members at the Rekihaku showed that a large part of the members were collected in the early Showa period when the temple was repaired. Radiocarbon dating determined that the members are from the multiple periods; ancient, middle and modern. The dating indicated the oldest members are from the 5th to 6th centuries.