Characterization of Funori - extraction of the red seaweed - as a restoration material [Original title and text in Japanese]

Funori is one of the traditional restoration materials in Japan, used as an adhesive agent and as a consolidant. Funori is the generic name that includes three kinds of red seaweed, Gloiopeltis tenax (Ma-funori), Gloiopeltis furucata (fukuro-funori), Gloiopeltis complanata (Hana-funori). For the restoration of Japanese paintings sheet-like Funori that is dried and bleached by sunlight is used. Restorers prepare their own Funori solution in their studios according to their own sense and experience. Funori solution shows different characters depending on the temperature during which they were extracted. In this report, we characterize the Funori solutions, which were prepared at room temperature and by heating. The solution which was prepared at room temperature had smaller molecular weight and low viscosity, while the solution which was prepared by heating had higher molecular weight and high viscosity. The result of centrifugation showed further precipitates in the solution prepared by heating than the other solution. Despite these differences, the adhesive force of Funori prepared at room temperature was higher than that of Funori prepared by heating. Since the purposes of using Funori in restoration vary, it is necessary to select a suitable way of preparing Funori solution.