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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 FROM AUTHOR]

One of the factors affecting the life expectancy of hanging scrolls is the storage environment. Our study focused on clarifying the degradation behaviour of painting paper, concentrating on the specific storage conditions that provide an airtight environment in a storage box and the stacked structure of the rolled paper rather than considering the materials of the wooden storage box or the gases generated from it. The degradation behaviour and rates for the sealed tube and moist heat ageing methods, excluding the additional effects of light and air pollutants, were compared. When the painting paper was immersed in a CuSO4・5H2O solution instead of a copper green pigment, the oxidation of the painting paper, attributed to Cu2+, proceeded faster with the sealed tube method than with the moist heat method. The co-occurring organic acids generated, namely glycolic and formic acids, which were secondary components, were detected in a higher amount in the first lining paper than the painting paper. This implies that the acids migrated from the painting paper into the lining paper. However, oxalic acid, which was the main component, did not significantly migrate and remained in the reaction system in the sealed tube without volatilising. This increased the hydrogen ion concentration in the painting paper and accelerated acid hydrolysis. Consequently, discolouration and a decrease in the degree of polymerisation and physical strength proceeded faster with the sealed tube method than with the moist heat method. Thus, although this result does not necessarily invalidate the storage system of a rolled hanging scroll in a box, the storage of a deteriorated hanging scroll in a closed system is expected to degrade the painting paper faster than it would in an open system. [ABSTRACT FROM AUTHOR]