Changes in the peel strength between the painting and first lining papers in Japanese scroll model samples

To maintain the permanence of a painting in a hanging scroll until subsequent repairs are made, inhibiting not only the deterioration of the painting and lining papers but also inhibiting decrease in the adhesiveness between them is important because the first lining process significantly influences the mechanical support to the painting paper by attachment. Several studies have been conducted on the deterioration attributed to each component of the lining system. This study evaluated the adhesiveness behaviour by peel strength in the lined complex depending on the painting and lining materials with varied concentrations, as well as the fibre type of the lining paper. The lined complex consisting of the untreated painting paper showed the highest initial peel strength owing to the significant cohesiveness of the wheat starch paste layer, which was attributed to the paper's higher wettability and permeability, even though substrate failure occurred with longer ageing times. Degradative materials such as Cu²⁺ attributed to pigments in the painting paper decomposed starch and decreased adhesiveness the fastest. Lined complexes coated with animal glue containing alum or Cu²⁺ in the painting paper maintained the lowest peel strength during ageing owing to lower wettability and permeability, resulting in interfacial failure between the animal glue and the wheat starch paste layer. In addition, adhesiveness varied with different fibre types of the lining paper, depending on combined factors such as fibre length, surface roughness, shape, and intensity of hydroxyl groups. Thus, variable conditions attributed to fibre characteristics, materials used for lining, and degradative products in the painting paper influenced the changes in adhesion and adhesiveness. This variation contributed to different lining effects that influenced the life expectancy of the hanging scroll and determined the efficiency of the subsequent repair work.