〔報文〕土質遺構露出展示保存のための基礎的研究―土中水のポテンシャル制御による遺構安定化の試み―

In this study, conservation method that prevents collapse of soil structural remains caused by drying and precipitation of salt by controlling the water potential gradient was examined. At Miyahata site located in Fukushima city, soil boring was performed to estimate the ground structure. In laboratory experiments, some parameters that determined water retention curve and hydraulic conductivity of unsaturated soil were estimated by evaporation method and inverse analysis with HYDRUS-1D. Based on the ground structure and unsaturated hydraulic properties obtained, water movement in vertical direction was simulated by numerical analysis. As a result of numerical analysis, it was revealed that the soil of remains would continue to dry. Then, the changes in water potential gradient caused by timely infiltration were also simulated. As a result, it was revealed that downward gradient of water potential and zero-flux plane could be produced alternately. By repeating infiltration and evaporation in a short span, it was revealed that deterioration of the remains caused by drying and precipitation of salt could be inhibited

〔報文〕高松塚古墳発掘／石室解体作業に伴う取合部・断熱覆屋使用木材等の防カビ対策：DDACの検討と施工

Takamatsuzuka Tumulus was excavated in 1972 and is known for its famous mural paintings on the plaster walls inside the stone chamber. However, after the tumulus experienced several outbreaks and damage by microorganisms, difficulty has been recognized in keeping the paintings in high humidity. Relocation of the mural stones and an archaeological excavation were performed in parallel in 2007. During the project, a tentative building was constructed in order to keep the relative humidity of the environment surrounding the stone chamber at about 90% to prevent exfoliation of the mural paintings. At the same time, the temperature was kept at about 10℃ in order to slow down the growth of molds on the mural paintings. But this high humidity was likely to encourage mold growth in the tentative building and an adjacent area in front of the stone chamber. So treatments with biocide, DDAC (1-Decanaminium, N-decyl- N, N-dimethyl-, chloride ), to wooden panels, timbers, sand bags and so on, which would be used in the front space and the tentative building, were performed. The selection of the chemical was based on: (1) relative low toxicity to humans (2) little odor and little emission of toxic volatile chemicals from treated materials, and (3) expectation of the duration of the effects for at least several months. Small tests on the effects of DDAC were performed. Wooden blocks, sugi (Cryptomeria japonica) and hinoki (Chamaecyparis obtusa), treated with/ without DDAC were placed in a glass jar of approximately 100% relative humidity at room temperature. After two weeks, mold growth was observed on an untreated block of sugi, but was not on a control block. After three months, there was no obvious signs of mold growth on DDAC-treated wooden blocks. Approximately 5% of the DDAC solution was applied to the materials by brush painting or spraying; then they were dried. The DDAC-treated materials were placed under high humid conditions of the Takamatsuzuka site for about three to several months during the excavation and relocation of the stone chamber in 2007. During these periods, no obvious mold growth was observed, which suggests successful treatment by this method

キトラ古墳保護覆屋内の環境について―温度・湿度と炭酸ガス濃度―

Kitora Tumulus is located in Asuka-mura, Nara prefecture and is thought to have been founded in the late 7th century. It is famous for its decoration with paintings of Chinese god beasts and animal servants on the walls of its stone chamber. Excavation started in 2004 and the relocation of paintings are now being executed. In this article, the environmental conditions in the conservation work of 2004-2005 are reported. Methods for controlling the environment of the buffer zone next to the stone chamber are also documented. It was made clear that sensors to measure humidity and carbon dioxide concentration did not have long life under especially high humid conditions of approximately 100% RH. However, it was found that a carbon dioxide sensor might detect the threat of explosive growth of microorganisms at an early stage

〔報告〕デジタル画像撮影による高松塚古墳壁画表面状態の調査

Since the discovery of full-colored murals in the stone chamber in 1972, the Takamatsuzuka Tumulus had been conserved on-site. However, in recent years, staining by molds and blurring of the murals have become serious issues. The Agency for Cultural Affairs (Bunkacho) decided, in 2005, to dismantle and move the stone chamber to a newly constructed facility for restoration. Restoration and various scientific investigations on the murals have been conducted since 2007. The purpose of this research is to acquire detailed visual information on the present surface condition of the murals by digital photography. A compact digital camera (Ricoh GX-100, about 8 million pixels) was attached to a specially designed frame, which surrounded the dismantled stone, to be facing the mural. This camera can take images of an area approx. 3.0 cm x 4.5 cm with the working distance of about 8.5 cm. Images were taken with slanting rays of white LED light illumination from the right. As a result, it was found that two different phenomena, besides molds, were concerned to the blurring of murals:　　i )　vanishing of painting materials from plaster　　ii)　appearance of milky-white solid substances on the plaster and painting materials. Milky-white substances in various forms such as paste, particle and sphere, were found distributed widely on all murals. These substances are assumed to be calcite, which eluted from the plaster by some reason. Identification and investigation on the cause of generation of these substances are to be considered in the future