Making Hon-Minoshi: Preparing the Raw Materials
Washi paper is made from plant fibers mixed with clean water and a viscous substance that prevents the fibers from clumping. Fibers are processed from the inner bark of kozo (paper mulberry), mitsumata (Edgeworthia chrysantha), and gampi (several shrubs of the genus Wikstroemia). When wet, the fibers bind at a molecular level, forming paper that is durable and resistant to tearing.
Hon-minoshi uses the white inner bark of Daigo nasu kozo from the town of Daigo in Ibaraki Prefecture. The long, silky bast fibers result in greater translucency than other plant fibers and produce lightweight, smooth, strong paper suitable for covering shoji screens, making lanterns, and for use in art conservation.
Kozo branches are harvested annually during the winter before the bark becomes hard and brittle. Bundles of kozo are steamed for around 90 minutes to soften the bark. The outer bark is then peeled off quickly by hand before the wood cools and the bark hardens. One hundred kilograms of kozo branches will yield around 4 kilograms of paper. The discarded core stems can be used for firewood.
The white inner bark (shirokawa) is spread out in the shallows of the Nagara River to be cleaned in running water and bleached by sunlight for a few days. Now, many papermakers work in large outdoor water baths fed by natural spring water or river water. The shirokawa is boiled with soda ash for several hours until it softens and can be separated into fibers, then the fibers are picked over to remove impurities.
The other key material for making washi is nebeshi, a viscous substance that is extracted from the roots of the tororoaoi (sunset hibiscus, Abelmoschus manihot) plant. The nebeshi is mixed with water and the pulped fibers to help the fibers disperse evenly and prevent clumping. The nebeshi is made by pounding the roots of the tororoaoi with a mallet in a mortar and leaving them to soak in water for several days, allowing the viscous substance to seep out of the roots. The resulting mixture is then filtered before being stirred into the water used in papermaking.