2015 Volume 52 Issue 1 Pages 069-077
Bakusho (airing) is a conventional method of preserving Chinese books and has been widely recognized as a method for removing humidity and pests. We hypothesized that there is another important purpose for this method: to volatilize organic acids that deteriorate the paper in books by surrounding the books with free airflow. This study investigated that possibility. First, the deacidification effect of bakusho was investigated. Bamboo paper, paper-mulberry paper, coated paper, and uncoated printing paper were subjected to moist heat treatment at 80°C and 65% RH for up to 16 weeks to accelerate aging. Lightness, tensile strength, folding endurance, and pH decreased most remarkably with bamboo paper that was moist heat-treated in an open state; however, it decreased less than equivalent paper treated in a sealed state, suggesting that exposure to air prevented paper deterioration. Next, after dry heat treatment at 105°C for 72 hours, a mock-up book made of bamboo paper was subjected to bakusho. Bakusho increased pH with exposure time. A shorter cycle of repeated heat treatment and bakusho maintained a higher pH. Bakusho performed in flowing air seemed more effective at recovering pH; the bamboo paper recovered pH earlier than when bakusho was performed in stationary air. However, bakusho treatment did not recover folding endurance that decreased during dry heat treatment.