纸质文物变色原因及脱色方法研究进展

本文针对纸质文物的载体——纸张的变色进行探讨。从纸张的原料组成如纤维素、半纤维素、木质素、树脂等方面分析了造成纸质文物变色的原因。为了恢复纸张原有的颜色,就必须破坏发色基团,包括将发色基团的共轭双键打开;将发色基团和助色基团分开;改变助色基团的化学结构;通过氧化破坏双键或侧链,减少发色物质;改变发色基团结构。目前常用的脱色方法有氧化法、还原法和液体光漂等。本文概述了常用的脱色方法的机理及用于纸质文物脱色的优缺点。各种方法对纸张都有一定的破坏作用。因此在决定进行脱色之前要根据实际情况选择合适的方法。选择脱色方法的原则是有效性和尽量小的危害,脱色后要进行彻底洗涤。

Progress of research on the mechanism of discoloration of paper relics and on methods of decoloration

Paper discoloration,which is related to the aging of cellulose,dust,mold,watermarks,painting pigments,etc.,affects the durability and appearance of paper relics and books in libraries.This paper discusses the causes of paper discoloration,based on the analysis of paper components, such as cellulose,hemicellulose,lignin and resin.To restore the original color of the paper,chromophoric groups must be destroyed either by opening conjugated double bonds,by separating chromophoric and auxochromic groups,by changing the chemical structures of chromophoric groups,or by oxidation of double bonds or side chains to decrease the amounts of chromophoric materials.Nowadays,the most widely used methods in the restoration workshops are oxidation bleaching,reducing bleaching and light aqueous bleaching.The decoloration mechanism of different methods and their effects on paper relics are reviewed.By comparison,it can be seen that all bleaching methods cause some damage to the paper.Their application on paper relics should be selected carefully according to different conditions.After bleaching,the paper should be washed thoroughly.