煉瓦造文化遺産の保存環境と塩類析出に関する調査:INAXライブミュージアム「窯のある資料館」を事例に

摘要

近代化遺産の保存に多くの関心が向けられるようになり，特に煉瓦造建造物の保存とその文化財登録はますます活発になっている。西洋では一般的な煉瓦造建造物であるが，日本ではそのほとんどが近代，つまり明治期以降のものであり，現在に至るまで実際に使用あるいは活用されている場合が多い。また，近年の近代化遺産の保存意識の高まりから，現在，修復あるいは保存方策を講じている物件も多い。%There is increasing interest in modern heritage, especially brick heritage, and its conservation and registration as cultural property have been examined actively. Many examples of brick heritage suffer from salt crystallization and, for the conservation of such heritage, it is necessary to eliminate supply of moisture and control the environment. As a basic study to examine deterioration and effective measures for conservation, surveys were conducted at the "Museum of Kiln" in the INAX Live Museum on June 30, July 7 and July 8,2016. The environment in the "Museum of Kiln" is air-conditioned and is not influenced by outside air. On the inner and outer walls of the kiln in the museum, various kinds of noticeable salt crystallizations were observed through analysis using an X-ray diffractometer:calcite(CaC0_3), thenardite(Na_2S0_4), epsomite(Mg_2S0_4.7H_20), astrakhanite(Na_2Mg(S0_4)2 • 4(H_20)), gypsum(CaS0_4 • 2H_20), aphthitalite(K3Na(S04)), eugsterite(Na4Ca(S04)3 • 2(H20)) and halite(NaCl). Depositions of thenardite were concentrated in the northern half of the kiln, whereas those of epsomite were confirmed in the southern half and the roof. Halite was identified only on the southeastern inner wall of the kiln, which was heated and dried by an indirect lighting placed near the wall. It seems that salt crystallizations tend to occur on brown bricks, which were made at low temperature, and cause significant deterioration. The possibility of using a portable X-ray diffractometer was also evaluated as a non-invasive analytical method for investigation of cultural properties on site.