Wholesaling Fine Japanese Papers for Conservation, Art and Craft
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  1. 1

    Raw Materials

    Originally, the term washi was reserved for paper made in Japan from Japanese native bast fibre. However, recently, paper made from non-native bast fibre or non-bast fibre is also referred to (and made available in the market) as washi. In order to avoid the risk of poor longevity or rapid deterioration, it is important to select the appropriate paper for your needs with an understanding of the differences between Japanese-grown bast fibre and non-native fibre.

    Washi (Japanese Paper) vs Youshi (Western Paper)

    When papermaking techniques were transmitted to Europe from China via the Middle East, paper was made from hemp and linen. Later, in Europe and elsewhere, cotton rags came into use. However, due to the shortage of raw materials in the nineteenth century, a grinding machine for ground wood pulp was developed, and by the twentieth century, paper made from wood pulp was manufactured in great quantities. Around the turn of the nineteenth century (during the Meiji period), machine papermaking techniques using wood pulp were introduced in Japan and the paper was called youshi (Western paper). These days, there are very few hand papermaking studios in the West, especially in North America and Europe, and daily use paper is mostly machine-made (both in the West as well as Japan).

    The main difference between washi made by the traditional method and youshi made by machine is the raw materials used. The problem with youshi made from ground wood pulp in the early period was that it deteriorated rapidly. The cause was lignin content in the ground wood pulp fibre. Lignin is hydrophobic and if present in large quantities, the swelling rate of the fibre decreases and it becomes difficult to break down the fibre during the pulping process. Paper made from lignin-rich wood pulp has poor hydrogen bonding between fibres, resulting in weak paper. Lignin is prone to deterioration and has a chemical reaction to (ultraviolet) light which prompts oxidation, thus paper containing lignin tends to discolour (yellow) and decrease in strength rapidly. Many books made of paper with mechanical wood pulp in the mid-nineteenth century are in extremely poor condition and have become troublesome conservation issues. These days, chemical pulp containing pure cellulose after the lignin has been removed, has become mainstream. Paper made from chemical pulp has less tendency to deteriorate. However, issues, such as residues of bleaches, continue to exist, and degradation over time still remains as a problem.

    On the other hand, bast fibre – the raw material used for washi – contains considerably less lignin (the inner white layer of bast fibre: 4.0-4.5%, Softwood: 25-33%, Hardwood: 20-25%). The bast fibre is cooked in an alkaline solution (e.g. wood ash or soda ash) in order to remove impurities such as lignin and pectin, leaving behind pure cellulose fibre. Wood ash and soda ash are both relatively mild alkali, and do little or no damage to the fibre during cooking. During sheet formation, formation aid (neri, or mucilage obtained from plants), is added into the vat with the bast fibre pulp, enabling the individual fibres to intertwine with one another on the papermaking screen (su), resulting in thin but strong paper.

    It should also be noted that there are cases where paper is made from a mixture of bast fibre and wood pulp in order to give thickness to the paper at a lower cost. In modern times, this kind of paper is often deemed “good enough” to meet the requirements at hand.



    Japanese Native Fibre vs Non-Native Fibre

    Washi, Japanese paper made in Japan, is usually made from bast fibre such as kozo, mitsumata and gampi. Recently, the use of non-native fibre grown in other countries has increased. Common imported materials are Thai kozo from Thailand or Laos, Philippine gampi (salago) and Manila hemp (abaca) from the Philippines, and mitsumata from China and Nepal (wood pulp and synthetic fibres are also used). In order to understand the quality of washi, it is important to know the differences between Japanese fibre and non-native fibre. For instance, very thin ‘Tengujo’ paper was originally made from Japanese native kozo, but these days Manila hemp is also used for some tengujo-type paper, and it has become difficult to judge the quality by paper names alone. It is ideal to be able to determine certain details about a paper, such as the raw material. However, it is also very important to understand that even in the case of Japanese native fibre, if it is bleached excessively and not rinsed properly, that too would result in washi of poor longevity. Washi made in the traditional method and from traditional materials is manufactured less and less these days, as new technologies and raw materials have been adopted. Washi has been manufactured for various purposes and the term ‘washi’ is now applied widely. Therefore, it is essential to purchase washi through a credible washi supplier who can provide necessary information on the products and advise you according to your needs.

    Mainly 3 types of bast fibre – kozo, mitsumata and gampi – have been traditionally used for washi made in Japan.

    Kozo
    Kozo fibre is wide and very long. During sheet formation, the fibres intertwine with one another on the surface of the papermaking screen, giving the paper great strength. This provides even thin sheets of kozo paper semi-transparency and a resistance to tearing. Kozo is used to make a vast variety of papers.
    Mitsumata
    Mitsumata fibre is narrow and relatively short. The fibre is known to contain a natural mucilage that helps disperse the fibres, but which makes the formation of thick sheets difficult. It has a smooth and shiny surface like gampi papers and is a light brown colour. Mitsumata is excellent for printing, and the fibre is used in Japanese banknotes.
    Gampi
    Gampi fibre is narrow and relatively short. Cultivation is difficult, so gampi is usually harvested wild in the mountains. The fibre is often used in combination with other fibres. It is also known to contain a natural mucilage that helps disperse the fibres, but which makes the formation of thick sheets difficult. Gampi paper is smooth, lustrous, and has its own natural resistance to insects. Gampi is well-known for its use for Torinoko paper and mimeograph paper.
    Fibre TypeAverage Length(mm)Average Width(μ)
    Kozo9.3727
    Mitsumata3.1619
    Gampi3.6020

    To select papers based on their raw materials, please search from the search field at the top-left of any page on this site, or refer to the Detailed Product Information available for each product.

  2. 2

    Chemicals Used in Papermaking

    When selecting washi for your particular needs, it is useful to know details about how the paper was made, such as the variety and amount of any chemicals used during the papermaking process, the pH of the final paper, and so on. In order to remove insoluble impurities from the raw material, it is necessary to cook the fibre in an alkaline solution. The variety and concentration of the solution vary depending on the papermaker, affecting the quality of washi.

    Natural Materials vs Chemicals

    During the washi making process, it is necessary to cook the fibre in an alkaline solution in order to remove insoluble impurities from the raw material, leaving behind pure cellulose. The alkaline solution dissolves the insoluble impurities into soluble components. Traditionally, wood or plant ash (potassium carbonate/potash) has been used to obtain an alkaline solution. In Kochi, where lime is readily available, slaked lime (calcium hydroxide) has been used for alkaline cooking. In the modern era, soda ash (sodium carbonate) or caustic soda (sodium hydroxide/lye) are also used for alkaline cooking. The degree of alkalinity and effect on the fibre vary depending on the alkali used.

    Traditionally, for handmade washi, mildly alkaline wood ash is used. Wood ash does little or no damage to the fibre and retains the original length of the individual fibres, but requires a long time to remove the knots and scars in the fibre after cooking. However, because this traditional technique is the least damaging to the fibre, it produces ideal papers for preservation. The papers made in this way are used for the purpose of restoring and conserving many important cultural properties at the national treasure level.

    On the other hand, caustic soda is a strong and aggressive alkali, and the most damaging to fibre, but it requires only a short time to remove the knots and scars in the fibre or does not require the fibre cleaning stage at all. Therefore, caustic soda is often used to cook non-native fibre or fibre for lower-quality paper.

    Both soda ash and slaked lime are relatively mild and their effect on the fibre is less damaging. Soda ash is commonly used to cook kozo, gampi, and mitsumata.

    Immediately after cooking, the bark is traditionally rinsed in water to remove the dissolved impurities. For example, ’kawazarashi’ is the process by which the cooked fibre is immersed in a river and exposed to sunlight. This provides a bleaching effect as well as removing the insoluble impurities. Such natural bleaching methods are the least damaging to the fibre.

    Since around the turn of the nineteenth century (the Meiji Period), various chemical products have become available and some bleaching agents have been adopted for use in Japanese papermaking. The agents, such as calcium hypochlorite (bleaching powder), sodium hypochlorite, or sodium chlorite have come to be used in some varieties of washi.

    When purchasing washi, it is essential to consider your purposes and refer to the product information for each paper to determine what chemicals have been used in its production.



    pH

    Generally, washi has a pH value of between 6.5 and 7.0. While acidic paper degrades rapidly, neutral paper (with a pH of close to 7) is suitable for long-term preservation. When judging the quality of washi, knowing the pH value is very helpful but is not always the most important factor depending on your needs and purpose.

    To select papers based on the chemicals used, please search from the search field at the top-left of any page on this site, or refer to the Detailed Product Information available for each product.

  3. 3

    Drying Methods

    After sheet formation and pressing, washi needs to be dried in order to remove any remaining moisture. There are a few drying methods and the quality of washi varies depending on how it is dried. It is essential to understand these differences when choosing washi.

    Wooden drying boards (itaboshi) have traditionally been used for drying. The paper is brushed onto boards one by one and dries relatively slowly in the sun, avoiding rapid shrinkage of the fibres. This method is more labour-intensive, but results in soft but strong washi, suitable for long-term preservation.

    Nowadays, there are various drying methods utilized. Using heated metal sheets for drying has become common. In the past, iron sheets were widely used, but the possibility of iron residues oxidizing and creating foxing (brown spots on the paper) were a problem. The use of stainless steel sheets has overcome this problem. However, the texture of paper dried on stainless steel sheets is somewhat stiffer than itaboshi, due to the rapid drying.

    To select papers based on their drying method, please search from the search field at the top-left of any page on this site, or refer to the Detailed Product Information available for each product.

  4. 4

    Handmade Washi and Machine-made Washi

    Nowadays, washi is made by hand or manufactured by machine. Generally, handmade washi is regarded as the highest quality, but there are some benefits with machine-made washi as well, such as a constant supply in stable quality and even thickness. It is appropriate to choose washi depending on your needs and purpose.

    Machine-made washi is manufactured on a large papermaking machine in large quantity and in a controlled environment. Thus, the level of quality is stable and the price is reasonable. Machine-made paper is suitable for large-scale, high-quantity, or low-budget projects.

    With handmade washi, preparation methods of the raw materials and the techniques of sheet formation vary depending on the papermaker and the area, giving each type of washi its own unique characteristics. Generally, handmade washi possesses a soft and warm, organic feeling. Therefore, searching through the wide range of handmade washi made by different papermakers in various areas to find the paper most suitable for your needs and preferences could be seen as a perilous adventure, but we prefer to think of it as treasure hunting!

    It is appropriate to select either handmade washi or machine-made washi depending on your needs and requirements.

    To select either handmade or machine-made papers, please search from the search field at the top-left of any page on this site, or refer to the Detailed Product Information available for each product.



    Summary of Key Points 1, 2, 3, and 4

    For conservation of Japanese National Treasures and Cultural Properties, washi made by hand from Japanese-grown bast fibre cooked with wood ash and dried on wooden drying boards is highly recommended. However, when the budget is limited or emergency treatments are required (e.g. a large conservation project of archival documents), it may be suitable to select appropriate washi by considering these key points – raw materials, chemicals, drying method, and production method.

    It is essential to purchase washi through a credible washi supplier who can provide the necessary information on the products and advise you according to your needs. Moriki Paper has a long history of trade with trusted papermakers and manufacturers of various papers, and supplies only washi which meets our high standards.