The Effect of Iron Ions from Prussian Blue Pigment on the Deterioration of Japanese Paper

Abstract

AbstractPaper is often damaged by ink or pigments containing transition metal ions. Damage of Kozo paper (a kind of Japanese paper) caused by iron ions from Prussian blue pigments (iron ferrocyanide) or by the acidity of dilute sulfuric acid during artificial ageing was studied. The degradation induced by iron ions is suggested to be a synergistic process consisting of hydrolytic and oxidative reactions. The degradation state of the cellulose polymer in Kozo paper was investigated using fluorescence labeling of carbonyl and carboxyl groups in combination with gel permeation chromatography-multiple-angle laser light scattering. In addition to cellulose, Kozo paper contains a relatively large amount of hemicellulose, which was characterized by determination of uronic acid and neutral carbohydrates. The amount of carboxyl groups in Kozo paper decreased during ageing. A decrease in the amount of uronic acid originating from the hemicellulose in Kozo paper is considered the dominant factor in the observed decrease of total carboxyl contents, even if the oxidative reaction would increase the number of carboxyl groups. The amount of uronic acid and xylose in hemicellulose was influenced by iron ions during ageing, indicating the decomposition of hemicellulose. This result suggested that the hemicellulose in Kozo paper were affected first and prevented the hydrolytic and oxidative degradation of cellulose, which might enable Kozo paper to last longer.