Tosa Washi is *one of Japan’s three major types of washi paper with over a thousand years of history in Kochi Prefecture, characterized by its thin yet strong and beautiful finish.
Long used for shoji screens and calligraphy paper, it is now beloved for a wide range of modern applications including art pieces, interior design, and stationery.
This article provides an easy-to-understand explanation of Tosa Washi’s appeal, how to choose it, practical uses, and storage methods to preserve its beauty for years to come.
This traditional craft is perfect for those looking to incorporate the warmth of natural materials into their daily lives.
*Japan’s Three Major Washi Papers: “Mino Washi” from Gifu Prefecture, “Echizen Washi” from Fukui Prefecture, and “Tosa Washi” from Kochi Prefecture
Table of Contents
Understanding the Basics of Tosa Washi: Start Here
Tosa Washi is one of Japan’s three major washi papers, a traditional craft that has been passed down in Kochi Prefecture for over a thousand years.
Known especially for its exceptionally thin yet strong properties among washi papers, it has been widely used for everything from calligraphy and printmaking to restoration paper for documents.
Its characteristics are supported by raw materials nurtured by clear streams and rich nature, as well as the advanced techniques of skilled craftsmen.
Here, we’ll explain in order the regional environment where Tosa Washi was born, its unique qualities combining thinness with strength, and the reliable labeling and designation systems.
Where Was This Paper Born? (The Kochi-Tosa Production Region)
Tosa Washi has been produced primarily in the mountainous areas of Kochi Prefecture, especially along the Niyodo River basin and in Ino Town.
This region is blessed with pure water and provides an ideal environment for growing high-quality kozo (paper mulberry), mitsumata (Oriental paperbush), and ganpi needed for papermaking.
The mountainous areas of Tosa have many rapid streams with few impurities in the water, making them ideal for the precise processing of fibers.
The Niyodo River in particular was selected as having Japan’s best water quality for four consecutive years starting in 2012 and is also called “Niyodo Blue,” providing an abundant source of cold water essential for papermaking. Craftsmen have worked to make maximum use of these natural conditions.
The combination of this climate and traditional techniques established Tosa Washi as a production region capable of supplying high-quality paper over long periods.
Even today, visitors can learn about the region’s history and techniques at the “Ino Town Paper Museum,” where washi continues to thrive as the center of local culture.
Is It Really Thin and Strong? The Unique Character of Tosa Washi
The greatest characteristic of Tosa Washi is its ability to achieve both “thinness” and “strength.”
Using kozo (paper mulberry) with long fibers as the main raw material, craftsmen carefully separate the fibers and create paper that weighs only a few grams yet resists tearing even when pulled by hand.
“Tosa Tengujoshi” in particular is called the world’s thinnest paper, achieving extreme thinness of 1.6 grams per square meter and 0.02 millimeters thick, making it indispensable for cultural property restoration and backing.
While maintaining this thinness, it has a beautiful translucency that brings out unique textures when used for calligraphy or printmaking.
It also has excellent humidity regulation and breathability properties with superior preservation qualities, offering the advantage of easy humidity adjustment depending on how it’s used.
Its applications are diverse, ranging from shoji screens and wrapping paper to modern uses in interior materials and lighting design.
This flexible adaptability is the unique character of Tosa Washi and the reason it has continued to be used across the ages.
Scientifically, kozo fibers are longer and stronger compared to other raw materials, serving as an important factor affecting paper strength and preservation properties, and these qualities support the quality of Tosa Washi.
Marks of Trust: Understanding Traditional Craft Designations and Labels
To receive this designation, strict standards are set for production region, raw materials, and techniques, guaranteeing that main processes involve traditional handicraft methods and over 100 years of history.
As a reliable indicator for consumers to purchase with confidence, look for products bearing the “Traditional Mark” (traditional certificate) label.
This is certified by the Japan Traditional Crafts Association and serves as an effective standard for distinguishing quality and authenticity. The design is by the renowned late designer Yusaku Kamekura.
There is also a labeling system by the “Kochi Prefecture Hand-made Washi Cooperative,” where products from member workshops are distributed as meeting established standards. In recent years, inexpensive machine-made washi and similar overseas products have appeared in the market, making it important to check for these labels.
Receiving direct explanations from craftsmen at exhibitions or direct sales locations also serves as a means to increase reliability. Understanding these labeling and certification systems allows you to properly select Tosa Washi and maintain a long relationship with it.
Tracing the Roots: Understanding History Reveals the Appeal
Tosa Washi is a traditional craft with over a thousand years of history, and understanding its journey makes its appeal even more prominent.
Its beginnings trace back to Shosoin documents from the Nara period, and by the Edo period, it had established a nationwide distribution network.
In modern times, ultra-thin paper called “Tengujoshi” emerged and became internationally recognized.
After experiencing postwar mass production and changing demand, the production region has continued new challenges. Connections with contemporary design and international markets are also advancing, showing an attitude of opening up the future based on history. Let’s examine this lineage in order.
From the Beginning to Edo Period Expansion
The origins of Tosa Washi trace back to the Heian period, with Tosa paper recorded as a major production region in the “Engishiki” (927 CE).
During the Heian period, it was used for official documents and sutra copying, and in medieval times it was treasured by temples, shrines, and warrior society.
Particularly during the Edo period, papermaking was encouraged by protective policies of the Tosa domain, with monopoly systems and official paper systems implemented, leading to significant growth as an industry.
The mountainous areas of Tosa were production regions for high-quality kozo and mitsumata, and papermaking utilizing clear streams supported unique high quality.
With expanding nationwide demand, diverse varieties such as shoji paper, hosho paper, and wrapping paper were created, and Tosa Washi was widely used from common people’s daily lives to official purposes. In the late Edo period, the domain established a monopoly system to protect regional distribution and quality, and this system became the foundation for the later washi industry.
The uniqueness as a paper production region strengthened its presence as it became more deeply embedded in daily life, establishing an indispensable position in Japanese culture.
The Emergence of Thin Paper (Tengujoshi) That Amazed the World
“Tengujoshi” born in 1880 (Meiji 13) became the catalyst for spreading Tosa Washi’s name worldwide.
Tengujoshi is washi made as thin as possible yet possessing surprising strength, feeling as light as a feather when held.
It became particularly essential for cultural property restoration and backing, with demand spreading internationally.
Scientifically proven to have uniform fiber entanglement with high strength and resistance to deterioration, it was valued for preserving rare books at world-renowned institutions like the Louvre Museum and British Museum.
Tengujoshi exists as more than just a product; it symbolizes the technical skill and creativity of Tosa Washi.
The techniques that craftsmen continue to inherit today continue to play an indispensable role in protecting cultural properties worldwide.
From Postwar to Present: Regional Challenges and Updates
In postwar Japan, the spread of Western paper led to a rapid decline in washi demand. The Tosa Washi production region also suffered a major blow, with many workshops forced to change businesses or close down. However, they found a path to survival by specializing in cultural property restoration and art applications.
From the high economic growth period onward, demand as shoji paper and packaging materials temporarily recovered, and the production region maintained its market position using high quality as its weapon.
In 1976, it received designation as a traditional craft, raising brand value while advancing collaboration with tourism and education.
In modern times, collaborations with different industries such as interior design, fashion, and lighting design have expanded, and Tosa Washi has broadened its sphere of activity into new areas of lifestyle culture. Furthermore, presentations at overseas exhibitions and joint development with designers have increased, raising its evaluation in international markets.
While there are challenges such as successor shortages, efforts continue to connect to the next generation through training systems and human resource development through school education.
The attitude of not just preserving tradition but updating it according to the times is perhaps the great appeal that modern Tosa Washi radiates.
How Is It Made? What Raw Materials and Techniques Are Used?
Tosa Washi creates unique textures through craftsmen’s handwork that takes advantage of the characteristics of plant raw materials. The representative raw materials are three types: kozo (paper mulberry), mitsumata (Oriental paperbush), and ganpi, each affecting the strength and texture of the paper.
Additionally, papermaking uses different techniques called “nagashi-zuki” and “tame-zuki,” which are used appropriately according to the intended purpose.
Furthermore, the drying and finishing processes determine the paper’s luster and surface texture, greatly affecting the expression of the finished product. Here we’ll explain in order from the characteristics of raw materials to differences in production methods and the artistry of finishing.
Organizing the Differences Between Kozo, Mitsumata, and Ganpi
The quality of washi changes significantly depending on the plant raw materials used.
- Kozo (paper mulberry) is the most commonly used raw material, with long, strong fibers that create paper that is thin yet resistant to tearing.
It is widely used for shoji screens, backing paper for preservation, and as support material for art works. - Mitsumata (Oriental paperbush) has short, smooth fibers that tend to create a lustrous finish.
It has excellent printing suitability and has been valued as banknote paper and high-quality printing paper since the Meiji era. - Ganpi has very fine fibers, resulting in supple, semi-transparent paper quality that yields beautiful paper with a high-class feel.
It was used as high-quality decorative paper in the Heian period and is still highly valued today for art restoration and high-end art materials.
Tosa Washi has created diverse paper types by using these raw materials appropriately according to their intended uses. Understanding the characteristics of these three types will reveal why Tosa Washi is internationally acclaimed.
Using Nagashi-zuki and Tame-zuki Appropriately
Papermaking techniques are broadly divided into “nagashi-zuki” and “tame-zuki.”
Nagashi-zuki is often used when kozo is the main raw material, where water is agitated while adding mucilage from tororo aoi to uniformly entangle fibers, creating thin paper with strength. Ultra-thin papers like Tengujoshi are created using this method, producing washi that combines uniformity with durability.
On the other hand, tame-zuki is a method suitable for fine fibers like ganpi and mitsumata, where water in the papermaking vat is kept still and allowed to settle all at once, resulting in smooth, high-density paper with translucency. Tame-zuki paper is treasured as decorative paper and high-quality calligraphy paper.
The difference between the two is not just technical but an important factor determining the paper’s intended use and desired texture.
Tosa Washi skillfully uses both techniques to achieve both strength and beauty, meeting diverse needs.
Texture Determined by Drying and Finishing
The final texture of washi is determined by the drying and finishing processes after papermaking.
Traditional methods use a drying technique called “ita-boshi,” where papers are individually attached to wooden boards and dried in sunlight. The smoothness and grain of the board are transferred to the paper, creating unique luster and suppleness.
From the modern era onward, indoor drying using stainless steel plates became widespread, allowing for smoother, more lustrous finishes in high-temperature, short-time processing.
Meanwhile, papers using traditional techniques retain the durability and texture unique to board drying.
After drying, the surface is polished and, when necessary, sizing (glue application) is applied to enhance strength and color development.
These finishing differences can greatly change the paper’s expression even with the same raw materials and papermaking methods. Craftsmen read weather and humidity conditions and determine optimal drying timing to maintain consistent quality. While drying and finishing are less visible processes, they are decisive points that affect the beauty and practicality of Tosa Washi.
What Types Are Available? Lineup to Know Before Choosing
While Tosa Washi is simply called “washi,” there are many types, and selection methods vary according to intended use and texture.
In addition to traditional representatives like Tengujoshi, Seichoshi, and Hoshoshi, there are also differences in dimensions and basis weight based on thickness and strength criteria, as well as practical papers specialized for shoji screens and cultural property restoration.
Choosing incorrectly can result in paper unsuitable for the intended purpose and difficult to use.
Therefore, here we’ll organize representative paper types for comparison, explain how to read basic dimensions and basis weight, and organize specific purpose-based lineups.
Comparing Tengujoshi, Seichoshi, and Hoshoshi
Three types representing Tosa Washi are “Tengujoshi,” “Seichoshi,” and “Hoshoshi.”
- Tengujoshi is called the world’s thinnest paper, with extreme thinness of about 0.02-0.05 millimeters yet boasting high strength and transparency.
It is essential for cultural property backing and restoration, and is also valued for art applications due to its beautiful translucency. - Seichoshi has long been used for record-keeping papers such as official documents, ledgers, and memorial registers, with excellent preservation and writing properties.
The unique screen marks from reed screen papermaking provide good ink development and writing feel, making it valuable for calligraphy, printmaking, and ancient document preservation. - Hoshoshi has a thick, smooth texture and dignified impression, making it widely used for formal letters, ceremonial envelopes, hanging scrolls, and correspondence.
It also has excellent durability, making it suitable for important documents and decorative purposes.
Comparing these three types, we can organize them as Tengujoshi for “thinness and strength,” Seichoshi for “record-keeping and preservation,” and Hoshoshi for “thickness and formality,” showing how each has fulfilled different roles.
Understanding Dimensions, Basis Weight, and Ream Weight (Basics to Avoid Mistakes)
When selecting washi, dimensions, basis weight, and ream weight specifications can be confusing.
Dimensions refer to the size of individual sheets, with traditional formats like “large format” and “half-cut” as well as standard sizes like A and B series.
Basis weight indicates weight per square meter and should be chosen according to intended use.
Thin papers like Tengujoshi have extremely light basis weights of about 10g/㎡, making them suitable for restoration and backing.
Ream weight is the weight (kg) of 1000 sheets of specified dimensions and serves as a distribution unit standard. Since ream weight numbers and reference sizes can differ and cause confusion, always confirm dimensions, basis weight, and ream weight when ordering. Without proper understanding of these specifications,
you might purchase paper that is too thick or too thin for practical use.
When selecting Tosa Washi, it’s important to carefully check dimensions and basis weight according to your work or intended use.
Proper understanding will reduce misunderstandings during ordering and inventory management while ensuring appropriate quality.
Purpose-Specific Papers: Shoji Screens, Restoration, and More
Tosa Washi also includes many types optimized for specific purposes.
For example, shoji paper combines breathability with durability and creates a Japanese home atmosphere by softly filtering light.
While thin, it is designed to resist tearing, reducing the effort required for replacement.
Restoration washi specializes in preserving cultural properties and ancient documents, with thin papers like Tengujoshi as representative examples.
These have high fiber uniformity and characteristics that don’t burden original materials when used for backing or reinforcement.
Furthermore, in recent years, washi processed for interior and lighting use, as well as modern products with enhanced printing suitability, have appeared.
These purpose-specific washi papers incorporate innovations that blend into modern life while utilizing traditional strengths.
With such a wide range of options available, it’s important to identify the paper that matches your specific purpose.
Tips for Storage and Maintenance for Long-term Use
To preserve Tosa Washi beautifully over long periods, proper environmental management and maintenance are essential. Since washi is a natural material, it is susceptible to effects from temperature, humidity, light, and acidic substances, with storage environment greatly affecting its lifespan.
Especially when handling it as cultural property or artwork, improper storage methods can lead to fading or deterioration.
Here we’ll organize practical knowledge for protecting washi, from basic temperature/humidity and pest control measures to actual handling materials and work precautions, as well as methods to prevent fading after artwork creation.
Basic Temperature/Humidity, Acidification, and Pest/Mold Prevention
The most important aspect of washi preservation is temperature and humidity management.
The ideal environment maintains temperatures around 15-20°C and humidity around 50%, with avoiding sudden changes being effective for long-term preservation.
High temperature and humidity invite mold and pest damage, while excessive dryness makes fibers brittle, requiring a stable environment.
Acidification risks also cannot be overlooked. Paper is affected by surrounding acidic gases and contact materials, with oxidation potentially causing brittleness.
Therefore, using neutral to weakly alkaline storage materials is recommended.
For pest control, regular ventilation and inspection are essential to prevent silverfish and booklice.
Using natural-origin pest repellents as supplements is also effective. By comprehensively combining these measures, Tosa Washi can maintain a lifespan of decades to over a century. Especially for collectors and museums, preventive management is the greatest protection measure.
Handling, Cutting, and Archival Materials
When handling washi, daily handling methods and choice of materials used are also important.
First, when touching directly by hand, clean gloves should be used to prevent oils and dirt from adhering to the paper. When cutting, use specialized cutters or knives that resist oxidation, and maintaining sharp blades directly affects the finish.
For preservation, archival materials such as neutral paper folders, acid-free linen tape, and polyester film are recommended. These contain no acidic substances and have properties that don’t cause paper deterioration during long-term storage.
Furthermore, boxes and cases for storing works should also be selected for excellent breathability and light-blocking properties.
During transport, methods combining bubble wrap and desiccants to protect from vibration and moisture are common. Such careful material selection and handling habits are important keys to passing Tosa Washi on to the next generation.
Preventing Fading and Deterioration After Artwork Creation
When washi is used for artwork, it spends increased time exposed to light and air as art pieces or crafts.
Particular attention should be paid to fading and deterioration at this stage. Ultraviolet light decomposes incorporated fibers and dyes, causing colors to fade.
Therefore, using UV-cut film or UV-cut acrylic during display and storage is effective.
Avoiding long-term display under strong lighting and adjusting illumination levels are also important. Furthermore, since oxidizing substances and dust in the atmosphere also cause paper deterioration, regular cleaning and use of filtered air conditioning are desirable.
Materials used for artwork backing and mounting should also be selected for neutrality and high stability.
In some cases, “rotation display” that alternates between storage and display by limiting exhibition periods can be effective. By incorporating such measures, Tosa Washi artworks can maintain their beauty over long periods.
Conclusion
Tosa Washi is a precise traditional craft completed through many processes from raw material selection to papermaking techniques, and drying and finishing.
For long-term relationships, measures against temperature/humidity and acidification, and prevention of insects and mold are essential. Furthermore, by implementing preservation using archival materials and UV protection during display, the lifespan as artwork or documents can be greatly extended.
With proper management and maintenance, the appeal of Tosa Washi will surely be passed on to the next generation.
