The history of wooden individually “cut-out gold letter” signage in Japan was discussed from the literature. It was inferred that the original type of “cut-out gold letter” signage was “carved letters ”signage with gold leaf on a single sawn wood (mainly Zelkova serrata), which had existed as a signboard for apothecaries since the early Edoperiod (late 1600s). Various types of signboards appeared with the development of commerce from the Edo period through the Meiji, Taisho, and Showa periods, and it is believed that the “cut-out gold letters” signboard spread widely because of the change in architectural styles that accompanied the reconstruction following the Great Kanto Earthquake in 1923. The newly appeared architectural style is so called “Signboard building”, because it was characterized by the decorated front facade covered with fire-resistant materials such as mortar, copper plates, and tiles, is a 2-3 story uniquely designed wooden store buildings. The“cut-out gold let-ters”are often placed directly on the façade of these buildings were for indicating the name of shop in Kanjicharacter (Chinesecharacter). The signboard buildings developed in Tokyo, the place of the earthquake reconstruction in the early Showa period, and immediately spread to other parts of Japan, especially the Kanto and Tohoku regions. These buildings can still be seen in Ishioka City, Kesennuma City, Hakodate City, and elsewhere. It seems to follow this trend that “cut-out gold letters” were installed on the facades of 2-4 stories undecorated shop buildings after World War Ⅱ (1945) in a great number of areas in Japan. Both types of buildings are going to be disappearing along with urban development and population decline, consequently these “cut-out gold letters” are also disappearing.
“Cut-out gold letter”is cut out from a piece of sawn wood with a fine grain such as Cercidiphyllum japonicum and Pinus parviflora, and the smoothed surface of each letter as a single piece is applied Urushi lacquer several times, and then all over the surface is pressed with gold leaves. Their outdoor durability was determined by visually observing based on the degree of peeling of the gold leaf, deterioration of the lacquer, and decay of the wood, comprehensively, at a distance of several meters. The degree of deterioration was evaluated on an 8-point scale from 0 to 7. If the degree of deterioration was less than 2 (the peeling of gold leaves is less thanhalf), the signboard was recognized as fare in appearance. The number of years to reach the degree of deterioration 3 (the peeling of gold leaves is more than half) was approximately 30 years after installation. Indeed, the signboard manufacturers recommended to the maintain it within less than around 15 years after installation.

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In Japan, the penetration area of preservative-treated wood is standardized by Japanese Agricultural Standards (JAS) and Approved Quality (AQ). The standards describe the use of a color reagent to identify the penetration area，but does not provide details on how to measure it. In this study, we developed a new program that efficiently measure the penetration area. Conventional measurement methods require at least three steps: drawing lines from the surface to a specific depth position, measuring the area of the unpenetrated region, and calculating the penetration area. With the method using this program, however, the measurement can now be completed in only one step, clicking on the corners of the test piece in the fastest case. In this report, we showed an overview of the penetration measurement using this program and confirmed the accuracy of the measurement. The results showed a maximum difference of 6% from the penetration area measured by the conventional method.

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