ITOH Takao Nara National Institute for Cultural Properties, Department of Cultural Heritage, visit researcher (70027168)
KUBODERA Shigeru Nara National Institute thy Cultural Properties, Department of Cultural Heriage, Ceneralmanager (00393372)
KURIMOTO Yasusi Akita prefeetvral University, Institute of Wood Technology, associate professor (60279510)
KANO Kenichiro Tokyo University of Arts, Institute ofArcientArtResearch, Instructor (60401486)
UMEMURA Kenji KYOTO UNIVERSITY, Research Institute for Sustainable Humanoshare, Assistant Professor (70378909)
清水 重敦 奈良文化財研究所, 文化遺産研究部, 研究員 (40321624)
|Budget Amount *help
¥15,520,000 (Direct Cost : ¥14,500,000、Indirect Cost : ¥1,020,000)
Fiscal Year 2007 : ¥4,420,000 (Direct Cost : ¥3,400,000、Indirect Cost : ¥1,020,000)
Fiscal Year 2006 : ¥3,400,000 (Direct Cost : ¥3,400,000)
Fiscal Year 2005 : ¥7,700,000 (Direct Cost : ¥7,700,000)
In Japan there are so many historical buildings. Especially, the ancient capitals Kyoto and Nara have many traditional wooden buildings, some of which are listed as a World cultural heritage of the UNESCO or as a National Property of Japan.
Wood used for the building materials might change its properties during usages. Therefore, the aging of wood can be of critical importance to traditional carpenters, Buddhist sculptors, art craftsman, museum curators and conservators as well as scientists in the field of art history, architectures, conservation science and wood science. Carpenters have an empiric and old knowledge that leads them to know when a timber needs to be changed. It is said also that they could be able to determine the age of a timber only observing it. They often identify age of wood with their naked eye. Features often used are color, odor, density and hardness. Thus the experience and judgment of them is vital.
Wood materials perform differently under various conditions. T
he degradation of wood is, in general, classified into three categories, i.e., weathering bio-degradation and aging. Aging is defined as a slow oxidation process caused by oxygen in the air. Therefore, based on the temperature-time conversion law an accelerated aging test was performed by heat treatment.
The main purpose of this study is to evaluate the durability and degradation of wood ; furthermore, it aims at obtaining an efficient and easy method to evaluate the strength of wood timbers in old structures like temples or shrines. This study aims at understanding and evaluating with a scientific way properties of an old timber.
First, Hinoki (Chamaecyparis obtuse) specimens were subjected to the heat treatment 180℃, 150℃, 120℃, and 90℃ respectively under various treatment time by normal oven method. An accelerated aging test was performed by heat treatment to obtain different levels of accelerated aging wood samples.
Secondly, naturally aged hinoki, some samples of Dr. J.Kohara old timber collections at the xylarium of RISH, were used. Oldest samples came from timbers of Horyuji Temple used in the 6th century. Horyuji Temple in Nara, at over 1300 years ago, is one of the oldest remaining wooden structures in the world. The age of these aged samples are measured by dendrochronology (Dr. Mitsutani, Nara National Cultural Properties Research Institute) and radioactive carbon chronology (Dr. Imamura, et. al. National Museum of Japanese history), respectively.
A comparison will be lead between mechanical and chemical properties of naturally aged wood and that of heat-treated wood. These results can be used as the standards in the comparison with the actual naturally aged wood materials. Future plan is to collect the old timbers from typical historical buildings to create a database of them, in the perspective of better understanding the history of wooden materials. Less