Materials
The inner barks of three plants — kozo, mitsumata and gampi — all native to Japan, are used primarily in the making washi.
Kozo (paper mulberry) is said to be the masculine element, the protector, thick and strong. It is the most widely used fibre, and the strongest. It is grown as a farm crop, and regenerates annually, so no forests are depleted in the process.
Mitsumata is the "feminine element": graceful, delicate, soft and modest. Mitsumata takes longer to grow and is thus a more expensive paper. It is indigenous to Japan and is also grown as a crop.
Gampi was the earliest and is considered to be the noblest fibre, noted for its richness, dignity and longevity. It has an exquisite natural sheen, and is often made into very thin tissues used in book conservation and chine-collé printmaking. Gampi has a natural 'sized' finish which does not bleed when written or painted on.
Other fibres such as hemp, abaca, rayon, horsehair, and silver or gold foil are some-times used for paper or mixed in with the other fibres for decorative effect.
Methods of Production
Branches of the (kozo, gampi or mitsumata) bush are trimmed, soaked, the bark removed, and the tough pliant inner bark laboriously separated, cleaned, then pounded and stretched.
The addition of the pounded fibre to a liquid solution, combined with tororo-aoi (fermented hibiscus root) as a mucilage, produces a paste-like substance when it is mixed.
It is this "paste" which is tossed until evenly spread on a bamboo mesh screen (called a su) to form each sheet of paper. The sheets are piled up wet, and later laid out to dry on wood in the sun or indoors on a heated dryer.
Washi
As Japan rushes with the rest of the world into the 21st Century, and more modern technologies take over, machines produce similar-looking papers which have qualities very different from authentic washi. As of the fall of 2008, there remained fewer than 350 families still engaged in the production of paper by hand.