Permanence of Washi (Japanese Paper) (Part II)
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PERMANENCE OF WASHI(JAPANESE (PART II)
PAPER)
MASAMITSU INABA AND RYUITIRO SUGISITA Tokyo National University of Fine Arts and Music, Faculty of Fine Arts, Conservation Laboratory, 12-8 Ueno Park, Taito-ku, Tokyo, 110, Japan ABSTRACT The change of degree of polymerization (DP), crystallinity and extent of oxidation during deterioration of Washi (Japanese paper) were studied. The extent of decrease of DP of cellulose in the Washi samples correlated with their acidity. The higher DP of cellulose in Washi fiber compared to that in wood fibers contributes to its permanency. It is reported that partial recrystallization of the amorphous regions in fibers during ageing results in a decrease of flexibility of the paper. From measurements of X-ray diffraction, less recrystallization of Kozo, Mitsumata and Gampi papers occurs during ageing treatment. This fact also contributes to the persistence of the strength of Washi through time. From measurements of infrared spectra of Washi samples, the amount of oxidation seems to be minimal. INTRODUCTION D6sa is a sizing agent for art objects made of paper consisting of animal glue and alum. It has long been utilized in traditional Japanese paper craft. When the pH of Washi (Japanese paper) goes below 5, the deterioration rate of the strength and discoloration increases with the decrease of PH. On the other hand, the pH decrease of Washi after applying d6sa depends on the buffering ability of the Washi. So the durability of Washi also varies according to its buffering capacity upon the addition of acid [1]. The dominant cause of the deterioration of paper by acids was thought to be the Amorphous region Crystalline region hydrolysis of cellulose [2]. Koura et al. [3] pointed out that partial recrystallization of cellulose molecules in microfibrils may contribute to fiber deterioration. Cellulose molecules align to form SAgeing a microfibril. In a microfibril, there are regions of good and poor alignment of cellulose chains. Those are called crystalline and amorphous regions, respectively. The recrystallization makes Fi g. 1 Schematic representation of the fiber stiff but brittle. the elementary fibril of When the acid hydrolysis cellulose to illustrate the reaction cleaves cellulose proposed aseing mechanism. molecules, recrystallization of the shortened cellulose ( A.Koura and T.Krause [3] ) Mat. Res. Soc. Symp. Proc. Vol. 185. 01991 Materials Research Society
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more easily achieved chains in the amorphous region is (Fig. 1). Oye tested deterioration rates of papers made of partially Partial delignification delignified mechanical pulps [4]. The strength of papers made of such fibers softened the fiber. the deterioration rates were faster However, was increased. Oye explained the extent of delignification. and related to this phenomenon by p
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