Kozo paper, usu-mino-gami, is frequently used as the first back lining paper of hanging scrolls in order to support the main paper with a painting or a work of calligraphy on it. To dye it an appropriate color, paper is often treated with an alkali mordant solution. However, current kozo paper products have received such comments from conservators that wet tensile strength is weak and hard to handle. Therefore, improving the wet tensile strength of kozo paper is required. In previous papers, the effect of the sheet forming method, cooking condition, and parenchyma cell content between fibers on the wet tensile strength of kozo paper has been investigated. In this paper, the effect of glucuronoxylan, the main component of hardwood hemicellulose on the wet tensile strength of kozo paper was investigated. The wet tensile strength of kozo paper, when made in different cooking conditions, was evaluated using the Finch device. Glucuronoxylan content in fiber was analyzed using GC-FID. According to the results, it has been proved that glucuronoxylan content (with a xylan to glucan molar ratio of 4.43% to 5.16%) itself contributes to the wet tensile strength of the kozo sheet. Therefore, to increase the wet tensile strength of kozo paper, it is recommended to cook under milder conditions, thus retaining a higher amount of glucuronoxylan in the pulp.

ABSTRACT To understand the degradation behaviour of rolled hanging scrolls for future conservation treatments, we evaluated the degradation–position profiles of naturally aged hanging scrolls and their model samples, which were subjected to different storage conditions. For the sample immersed in a CuSO₄・5H₂O solution and rolled around a glass rod, accelerated ageing using the open method (80°C, 65% RH) revealed a tendency of lower pH and higher discolouration towards the central positions, where rolling caused the most tightness. However, no clear tendencies were observed for the concentration variations of organic acids. The degradation effects of the organic acids emitted from the paulownia wooden box were also examined using the sealed tube method by enclosing the rolled painting paper and acidic paper containing organic acids together in a glass tube. Large amounts of oxalic and formic acids were detected at the periphery and scant migration of the organic acids was observed towards the centre, thus indicating that the central positions of the painting paper were less susceptible to the influence of the organic acids emitted from the external environment. By contrast, glycolic acid diffused towards the centre. The analysis of two naturally aged hanging scrolls showed different degradation behaviours. One sample, stored open in the rolled state, showed severe discolouration with the naked eye at the outermost back surface of the scroll. This was possibly associated with the large amount of sulfate ions originating from the external atmosphere, which kept the pH lower and increased discolouration towards the peripheral positions of the painting paper. For the sample stored in a paulownia wooden box, discolouration was not observed with the naked eye at the outermost back surface of the scroll, although lower pH and higher discolouration were observed towards the central positions.

ABSTRACT Volatile organic compounds (VOCs) generated from naturally aged Japanese hanging scrolls and their model samples were measured using solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) to clarify the effect of different painting papers and raw materials on the degradation state of hanging scrolls. VOC-based degradation markers were identified and their applicability was considered for degradation evaluations of actual Japanese hanging scrolls. The relative peak areas of different VOC groups were calculated by normalising their peak areas to the total peak area of long-chain hydrocarbons. When a painting paper was immersed in a CuSO₄・5H₂O solution, or coated with an alum solution, the relative peak areas of furfural and carboxylic acids increased after accelerated ageing, while these relative peak areas decreased when animal glue was applied, indicating that animal glue inhibited the generation of VOCs. When the painting paper containing Cu²⁺ was stacked with lining paper, furfural and carboxylic acids migrated into the lining paper with ageing. Animal glue coated on the painting paper retarded this migration into the lining paper. For the lining paper coated with wheat starch paste, the relative peak areas of furfural, carboxylic acids, and aliphatic aldehydes did not change significantly with ageing, indicating that wheat starch paste did not contribute to paper degradation, although these relative peak areas increased when aged wheat starch paste was applied. These results indicate that the targeted VOCs are valid degradation markers of Japanese hanging scrolls.

Acetic acid and formic acid, emitted from wood and wood-based building materials, are important agents of metal corrosion and discoloration in museum artifacts. The use of low-emission wood-based materials in the design and construction of display cases or storage facilities offers a straightforward approach to mitigating such chemical emissions. In this study, we applied an established mathematical model to analyze the emission behavior of acetic acid and formic acid from wood-based materials, with consideration of their non-uniform and time-dependent characteristics. The applicability of the double-exponential model for acetic acid and the first-order decay model for formic acid was examined using plywood, solid wood, and wood flooring specimens. Furthermore, through numerical analysis, we developed a method to compare the relative emission amounts of different materials. Our findings provide insights into the long-term emission characteristics of acetic acid and formic acid and offer useful indicators for selecting appropriate materials for museum environments.