Effect of Cooking Method on Wet Tensile Strength of Kozo Paper

Abstract

Usu-mino-gami （a kind of thin kozo paper） is frequently used as the first back lining paper of hanging scrolls in order to support the main paper with a painting or a work of calligraphy on it. For dying appropriate color, the paper is often treated with alkali mordant solution. However, current usu-mino-gami product received such comments from conservators that wet tensile strength is weak, and hard to handle. Therefore, improving wet tensile strength of kozo paper have to be required. In our previous paper, the effect of sheet forming method on wet tensile strength of usu-mino-gami has been investigated. In this paper the effect of cooking method on wet tensile strength of kozo paper was subsequently investigated. Wet tensile strength of kozo paper which made with different cooking conditions, was evaluated using Finch device. Kozo paper with different amount of parenchyma cell was also be made. The amount of parenchyma cell in pulp was measured with area ratio of parenchyma cell films between fibers on kozo sheet by using scanning electron microscope （SEM） images. According to the results, the increase of wet tensile strength and higher amount of parenchyma cell were observed with shorter cooking time, and lower concentration of cooking agent （alka-line）. Furthermore, wet tensile strength of kozo paper increased when amount of parenchyma cell in pulp was higher.