Résumé
Wood is a material designed by nature to last as long as it is not attacked by biological agents. It can support trees for centuries, and as a technological material it can again sustain loads for considerable periods. It is, as a consequence, a major component of the cultural heritage of many civilisations and the assessment of wood properties from ancient objects is a question of fundamental and practical interest. One major difficulty for such research is the gathering of suitable samples, with well-defined origin, certified dating and permission of publication by conservation administration. The Japanese context, where traditional uses of wood have been maintained for more than 1600 years, offers a unique opportunity to address the question of wood aging. Hinoki (Chamaecyparis obutusa) samples from Horyuji temple in Nara and other famous historical Japanese buildings have been gathered for more than 10 years by RISH, Kyoto University, expanding a collection gathered in the 50ties by Jaro Kohara. The wood age, defined as the time elapsed since wood formation and estimated by dendrochronology cross-checked with 14C measurements, ranged from 600 to 1700 years. The time elapsed since tree felling was also considered whenever possible. The recent wood used for comparison was selected according to similar origin and quality from craftsman viewpoint. The observations made included bending tests in L and R directions, colour measurements using a spectrophotometer, chemical and thermomechanical analysis.