This review summarizes recent studies related to the property of “wood as a visual stimulus.” Warm colors, varied grain patterns, and mellow gloss are attractive surface features of wood, and have impacts on the psychological and physiological states of observers. On the basis of marketing researches which reveal the psychological structure of consumer “preference” for wood products, many studies done abroad indicate that surface appearance greatly affects preferences. On the other hand, in some Japanese researches the surface appearances of wood are computed quantitatively and the relations between such image characteristics and the psychological responses of human observers are examined. Furthermore, grain pattern generators, which can express any lumber surfaces using computer graphics, are developed to implement them in a product design system. The wooden interiors are constructed by various types of lumber and wood based materials. Experimental investigations which examine the visual effects of wooden interiors are shifting from the visual evaluation of interior photographs to measurements of psychological and physiological responses of subjects who are exposed to full-scale wooden interiors.

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When a tree reaches 10 years of age, heartwood is formed in the central parts of stem and branches. The characteristics of heartwood greatly affect the properties of the wood, such as color tone, order and durability, which are very important in practical use. In addition to these, the botanical scientific interest in the understanding of the significance of a tree's forming of heartwood and also in the clarification of the mechanism of heartwood formation have long drawn the attention of researchers to research on heartwood and heartwood formation. Heartwood formation is a complicated physiological tree phenomenon involving biological, chemical, and physical changes. Among them, the materials unique to heartwood, specifically, generated and accumulated heartwood extractives, are the consequences of chemical changes. As these chemical compounds often have their own properties of color, order and antibiotic activity, the phenomenon at the time of heartwood formation is the most remarkable change phenomenon, so that it can be directly related to the expression of the wood properties. In this review article, heartwood formation is explained mainly through “the accumulation of heartwood extractives” from physiological, biochemical, histochemical and molecular biological viewpoints.

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We investigated the effect of hot-pressing as a pre-treatment for prevention of surface checks in sugi (Cryptomeria japonica D.Don) columns with pith. In order to find an effective condition for prevention of surface checks and to obtain fundamental knowledge of hot-pressing surface treatments, we particularly investigated the effect of hot-pressing surface treatment for formation of drying set in the sugi column surface. Hot plate temperature was set at three levels: 150, 180 and 210°C. Press time was set at two levels: 30 and 60 min. As a result, the intensity and the depth of drying set increased with hot plate temperature and press time. Drying set was formed to a maximum depth of 7 mm. On the other hand, moisture content decreased to less than 10% at the specimen surface on 180°C, 60 min and 210°C, 60 min treatment conditions, but the moisture content increased at the inside. It was suggested that the drying set which was formed in the sugi column surface by the hot-pressing surface treatment in a short time and its intensity are about the same as with the conventional high temperature drying method.

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The effect of hot-pressing as a pre-treatment for prevention of surface checks in sugi (Cryptomeria japonica D.Don) columns with pith was investigated. The effect of surface treatment was examined by occurrence of surface checks after drying treated sugi columns 3 m long. Hot plate temperature was set at 200°C and press pressure was set at 0.1∼0.15 N/mm². Treatment time was set at three levels: 30, 60 and 90 min. As a result, there was no significant difference in surface checks between treatment times of the treated specimens. Also, the surface checks area in every one of the treated specimens was controlled to one eighth of that in untreated specimens after drying. On the other hand, internal checks occurred on 60 and 90 min treatments and increased with the treatment time.

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The needle essential oils of Pinus thunbergii and Cryptomeria japonica were analyzed by GC and GC/MS, and the water solubility and the bioactivities of the oils and their components were examined. In addition, relationships between solubility and bioactivity were investigated. The needle oils of P. thunbergii and C.japonica exhibited solubilities of 26.2 and 21.9 (mg/L), respectively. For components, α-, β-pinene had low solubilities of 1.7 and 2.1 (mg/L), respectively, and α-terpineol and terpinen-4-ol had high solubilities of 70.7 and 81.1 (mg/L), respectively. The water solubility of oxygenated monoterpenes was greater than those of needle oils and monoterpene hydrocarbons. With regard to germination rates of radish seeds, after 1 day of the test, when the concentration of the needle oils and the components were 5ppm, the rates from needle oils (P.thunbergii and C.japonica), α-terpineol and terpinen-4-ol were 11.9, 4.8, 0 and 2.4 (%), respectively, and controlled low. In relating termite (Reticulitermes speratus) mortality, lethal concentration of 50% (LC₅₀) of needle oils (P.thunbergii and C.japonica), α-terpineol and terpinen-4-ol were 60.3, 34.8, 8.6 and 6.3 (ppm), respectively. Bioactivities of oils and the components were recognized. Thus, for oils and the components, the increased water solubility corresponded well with the decreased germination rate and LC₅₀ of termites. It was suggested that water solubility and the bioactivities of needle oils are affected by those of oxygenated monoterpenes (α-terpineol and terpinen-4-ol).

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