The Effect to Physical Properties of Bamboo Paper with Different Cooking Agent

Abstract

Handmade bamboo paper was frequently used for printing and drawing since the Tang dynasty (618-907 AD)in China because of its features of strength and flatness. Regarding rare books, the share of using bamboo as the raw material for making paper is said to be around seventy percent. Also Japan has been using bamboo paper in terms for either the collection of rare books or diversified purposes such as painting by importing them from China too. For conservation of these cultural objects on bamboo paper, we are expecting and required use better quality bamboo paper, but cannot get the equivalent quality of paper as in the past. The traditional way of making bamboo paper is to get the raw bamboo shoots to be fermented in slaked lime first. Afterward the cold digestion method and hot digestion method will go through the process without alkali cooking and with alkali cooking respectively. The air dried fermented raw bamboo fiber(Mosochiku：Phyllostachys pubescens)which was collected in Jiangxi province, China were cooked with caustic soda(NaOH) , soda ash(Na 2 CO 3)and lime(Ca (OH) 2) ， to the result of a cooking rate which was lower in that order. The physical strength of ISO folding number was decreased greatly for lime cooked paper which yields at 84%(L84)because of long cooking hours. The purpose of this research is to study the effect of cooking agent on durability of 5 kinds of handmade bamboo papers. The bamboo papers have been coated with acidic Dosa sizing solution(traditional surface size including animal glue and alum for Japanese painting)with normal and higher concentrations. Then the moist heat ageing test was done under the conditions of 80℃＋65% rh, from 1 week to 8 weeks. The changes in color, pH, physical strengths(Folding Endurance and Tear Index)were measured. We found that the initial pH of all original papers remained in the range of 8.7 to 9.2 without the acidic Dosa sizing. Even the pH stayed above 7.9 when a high concentration acid sizing solution was coated in advance. The changes in physical strength resulting from moist heat ageing were quite small due to the alkalinity of the bamboo paper. The discoloration rate during ageing for lime cooked papers(i.e. L94, L84)were smaller than the other papers at the same pH value. In onclusion, the durability of bamboo paper cooked with caustic soda and soda ash is better than with slaked lime.