Washi is traditional Japanese paper handmade from kozo, mitsumata, and gampi fibers. Learn its thousand-year history, how it is made, its role in art and conservation, and why it lasts.
A single sheet of washi paper measuring one square meter can weigh just 2 grams and resist tearing when you pull it with both hands. This combination of thinness and strength is what makes washi unlike any other paper in the world. In 2024, the world's thinnest washi paper, produced by Hidakawashi Co. in Kochi Prefecture, measured 0.02 millimeters thick. Museums and libraries around the world use it to repair ancient documents, books, and artworks. The same paper that protects medieval manuscripts in the National Archives of Japan is used by printmakers, calligraphers, and bookbinders for its durability and beauty. Washi was registered on UNESCO's Representative List of the Intangible Cultural Heritage of Humanity in 2014, recognizing a craft that has been practiced in Japan for over a thousand years.
Washi is traditional Japanese paper made from the bast fibers of three plants: kozo (paper mulberry, Broussonetia), mitsumata (Edgeworthia chrysantha), and gampi (Wikstroemia sikokiana). The term "washi" was coined during the Meiji period (1868-1912) to distinguish Japanese handmade paper from Western machine-made paper, which was called "yoshi." Today, the term encompasses both handmade and machine-made Japanese paper, though the highest quality washi is still made by hand using techniques passed down through generations. Washi is valued for its strength, translucency, and longevity, which come from the long fibers of the plants used to make it.
This entry covers the history of washi, the three fibers that define it, how it is made, and its role in art and conservation.
The secret of washi is in the fibers. Kozo fibers are exceptionally long, typically 10 to 15 millimeters, compared to about 1 to 3 millimeters for wood pulp fibers. These long fibers interlock and bond tightly when formed into sheets, producing paper that is strong, flexible, and resistant to tearing even when wet. Kozo fibers are also naturally low in lignin, which means washi does not yellow or become brittle over time. A 2023 study published in the European Physical Journal Plus analyzed Japanese woodblock prints from the Taisho period and confirmed that the preservation and longevity of these prints depends largely on the physicochemical characteristics of the washi paper supports. Read the study at European Physical Journal Plus.
The three fibers used in washi each produce paper with different qualities. Kozo produces the strongest, most durable paper, with a coarse texture and natural cream color. It is the most commonly used fiber for washi. Mitsumata produces a softer, smoother paper with a slight sheen, used for calligraphy and stationery. Gampi produces the finest, most translucent paper, historically used for formal documents and luxury paper. It is the rarest and most expensive of the three because gampi is difficult to cultivate and is mostly harvested from wild plants.
Papermaking was introduced to Japan from China around the 7th century, about 500 years after paper was invented in China. According to the Kogei Japonica guide to Tosa Washi, the origins of Tosa Washi trace back to the Heian period, with Tosa paper recorded as a major production region in the Engishiki, a compendium of Japanese regulations compiled in 927 CE. By the Edo period (1603-1867), washi production had established a nationwide distribution network, with regional specialties developing in different parts of Japan. Read more at Kogei Japonica.
During the Edo period, papermaking was encouraged by protective policies of regional domains. The mountainous areas of Tosa (modern Kochi Prefecture) were production regions for high-quality kozo and mitsumata, and papermaking utilizing clear streams supported unique quality. The domain established a monopoly system to protect regional distribution and quality. Diverse varieties were created, including shoji paper for sliding screens, hosho paper for calligraphy, and wrapping paper for commercial use.
The Meiji period (1868-1912) brought Western papermaking technology to Japan. The term "washi" was coined to distinguish traditional Japanese paper from the new machine-made "yoshi." According to the European Physical Journal Plus study, the production methods of washi underwent transformative changes in response to competition from yoshi, including the introduction of chemical resources like caustic soda for processing and the use of rice flour and clay as additives. Despite these changes, handmade washi production continued to thrive.
In 1976, Tosa Washi was designated as a National Traditional Craft in Japan, officially recognizing its quality and cultural value. In 2014, UNESCO registered "Washi, craftsmanship of traditional Japanese hand-made paper" on its Representative List of the Intangible Cultural Heritage of Humanity, covering three washi-producing regions: Mino in Gifu Prefecture, Niyodo in Kochi Prefecture, and Hamada in Shimane Prefecture.
The traditional washi-making process is labor-intensive and seasonal. According to the Tokyo National Research Institute for Cultural Properties, which conducted a field survey of kozo cultivation in Nara Prefecture in June 2025, the process begins with harvesting kozo branches in winter. The bark is steamed, stripped from the branches while still hot, and cleaned. Dark outer layers of bark are removed, leaving the white inner bark. The inner bark is then cooked in an alkaline solution, traditionally made from wood ash, to separate the fibers.
The cooked fibers are beaten with wooden mallets to separate and spread them. The beaten fibers are suspended in water with a viscous plant mucilage called neri, extracted from the roots of the tororo-aoi plant (sunset hibiscus). The neri prevents the fibers from clumping together and allows them to disperse evenly in the vat. The papermaker dips a bamboo screen (su) mounted on a wooden frame (keta) into the vat and pulls it up with a smooth motion. The fibers settle on the screen in an even layer, and the neri allows the papermaker to control the thickness by layering multiple dips.
The wet sheets are removed from the screen, stacked, and pressed to remove excess water. The pressed sheets are then brushed onto flat surfaces, traditionally wooden boards or drying racks, and left to dry in the sun and wind. The result is a sheet of paper with a natural, slightly irregular texture and visible fiber patterns.
The TOBUNKEN survey notes that the number of people responsible for kozo cultivation is decreasing year by year, posing a significant challenge for ensuring a stable supply of raw materials. The issue of securing wood ash for the cooking process is also becoming increasingly difficult, as traditional sources of wood ash become harder to procure.
Washi is the paper on which Japanese ukiyo-e woodblock prints were printed, and still are printed. Hokusai's The Great Wave off Kanagawa (c. 1831), Hiroshige's The Fifty-three Stations of the Tokaido (1833-1834), and Utamaro's bijin-ga portraits were all printed on washi paper, typically made from kozo fibers. The strength of the paper allowed it to withstand the repeated impressions of the baren (the rubbing tool used to transfer ink from block to paper), and its absorbency allowed the water-based inks to soak in and create the soft, luminous colors characteristic of ukiyo-e. The survival of ukiyo-e prints from the 18th and 19th centuries in good condition is a direct result of the archival quality of the washi they were printed on.
Washi is the preferred surface for sumi-e (Japanese ink painting) and calligraphy. The absorbency of the paper allows the ink to bleed and gradient naturally, creating the expressive brushwork that defines these traditions. Different types of washi are used for different effects. Hosho paper, a thick, soft kozo paper, is traditionally used for calligraphy. Gasenshi paper, which contains a small amount of kaolin clay, is used for sumi-e because it absorbs ink in a way that enhances the tonal range of the brush strokes.
Contemporary printmakers use washi for intaglio, relief, and lithographic prints. The thinness and strength of washi allow it to pick up fine detail from printing plates, and its archival quality ensures that the prints will last. Japanese printmakers and Western printmakers alike use washi papers like hosho, kozo, and gampi for their work.
Washi is the standard paper used in art conservation for repairing tears, backing damaged works, and reinforcing weakened paper. The thinness of washi allows conservators to apply patches that are nearly invisible, and the strength of the kozo fibers ensures that the repair will hold. Hidakawashi Co. in Kochi Prefecture produces washi specifically for conservation, including an ultrathin paper weighing 1.6 grams per square meter used to repair old masterpieces and Noh costumes. The Asahi Shimbun reports that the company has become a savior for libraries, museums, and galleries desperate to repair discolored or brittle pages in books and artworks.
The three regions recognized by UNESCO are Mino (Gifu Prefecture), known for its translucent paper used for lanterns and shoji screens; Niyodo (Kochi Prefecture), known for Tosa Washi, characterized by its thinness and strength; and Hamada (Shimane Prefecture), known for Sekishu Washi, used for calligraphy and printmaking. Each region has its own traditions, fiber sources, and techniques, though all use kozo, mitsumata, or gampi as their raw materials.
Tosa Washi was designated as a National Traditional Craft in 1976. The Kogei Japonica guide notes that the greatest characteristic of Tosa Washi is its ability to achieve both thinness and strength, using kozo with long fibers as the main raw material. Scientifically, kozo fibers are longer and stronger compared to other raw materials, which is the key factor affecting paper strength and preservation properties.
Washi is related to rag paper, the Western tradition of paper made from cotton and linen fibers, in that both are valued for their archival quality and strength. It is the traditional surface for sumi-e (Japanese ink painting) and ukiyo-e (Japanese woodblock prints). For the broader category of paper used in Western art, see our entry on watercolor paper. And for a deeper dive into art materials, read our post on oil painting techniques to understand how the choice of surface shapes every painting medium.
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