Several accelerated weathering tests were conducted using uncoated sugi (Japanese cedar, Cryptomeria japonica D. Don) heartwood or sugi coated heartwood with penetrating or film-forming coating; test S (standard) based on JIS K 5600-7-7^:2008 (filtered xenon-arc radiation, method 1, cycle A, 38°C, irradiance 60 W/m²), tests W2 and W3 with 2-fold and 3-fold water spray, tests T48 and T58 performed at 48°C and 58°C, and tests C1 (3-fold water spray, 48°C, 1.75-fold irradiance) and C2 (3-fold water spray, 48°C, 2.5-fold irradiance). We found that C2 was the fastest among these tests, and we were able to estimate the changes in the wood during natural weathering in Tsukuba city by tilting 45° south facing 2.2 to 8.9 times faster compared with the S test.

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Anti-termite field tests were conducted at a coastal pine forest site in Kagoshima, Japan. Sugi (Cryptomeria japonica), Hinoki (Chamaecyparis obtusa), and some other imported lumbers treated with disodium octaborate tetrahydtate (DOT) were tested under non-exposure (above ground and protected from rain) conditions. Small test pieces of 30 (T) x 30 (R) x 150 (L) mm, and 120 (T) x 120 (R) x 1000 (L) mm of the structural lumbers (the lumbers were followed to cut into 200 mm in length after impregnation), were used for the tests. Impregnated amounts of DOT were generally more into the sapwood than the heartwood of Sugi in small test pieces, however, large differences were not seen between the sapwood and the heartwood of Hinoki. In the case of structural lumbers, sufficient amount of DOT was not impregnated into Sugi and Hinoki without pressure process after vacuum. Even after pressure process, impregnated amounts of DOT were less into the imported species. Termite attack started earlier at the test field for structural lumbers than that for small size test pieces. As a result of four years observation, DOT impregnated materials will be able to expect sufficient resistance against termite attack under the non-exposure condition, if the impregnated amounts of the DOT can be properly secured (more than 3% boric acid equivalent).

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