Washi (Japanese Paper) vs Youshi (Western Paper)

When papermaking techniques were transmitted to Europe from China via Middle East, paper was made from hemp, linen and cotton rags. However, due to the shortage of raw materials in the 19th century, a grinding machine for ground wood pulp was developed and by the 20th century paper made from wood pulp was manufactured abundantly. During the Meiji period, machine papermaking techniques using wood pulp was introduced and the paper was called as youshi (Western paper). These days, paper used daily are mostly machine-made in the West as well as Japan.

The main difference between washi, which has been made in the traditional methods, and youshi, which are made by machine, is raw materials used. The problem with youshi made from ground wood pulp in the early period was it deteriorated rapidly. Its cause was lignin contents in fibre of the ground wood plulp. Lignin is hydrophobic and if it exits in large volume, swelling rate of the fibre decreases and it would become difficult to fibril the fibre during the pulping process. Paper made from lignin rich wood pulp has poor hydrogen bonding among fibres, resulting weak paper. Lignin is prone to deterioration and chemical reaction by light (ultraviolet) prompted oxidation, thus paper containing lignin tends to discolour (yellow) and decrease strength rapidly. Many books made of paper with mechanical wood pulp in the mid-19th century were in extremely poor condition and became troublesome conservation issues. These days, chemical pulp, containing pure cellulose after lining being removed, has become the main stream. Paper made from chemical pulp has less tendency to deterioration. However, the issues, such as residues of bleaches, exist and degradation over the time still remains as problem.

On the other hand, bast fibre, the raw materials used for washi, contain less lignin (bast fibre/shirokawa-inner white layer: 4.0-4.5%, Softwood: 25-33%, Hardwood: 20-25%). The bast fibre is cooked with alkaline solutions (e.g. wood ash and soda ash) in order to remove impurities such as lignin, pectin and to obtain necessary cellulose fibre. Wood ask and soda ash are weak and mild alkali respectively and does not damage fibre during cooking. During the sheet formation, formation aid (neri), mucilage obtained from plants, is added into the vat with bast fibre pulp, which enables the fibre to entangled each other on the papermaking screen (su), resulting thin, but strong paper.

Japanese Native Fibre vs Non-Native Fibre

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

Natural Materials vs Chemicals

During washi making process, it is necessary to cook barks in alkaline solution in order to remove insoluble impurities from the raw materials, leaving cellulose only. Alkaline solution would solubilise insoluble impurities into soluble components. Traditionally wood or plant ash (potassium carbonate/potash) has been traditionally used to obtain alkaline solution. In Kochi where lime is locally obtained, 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. Concentration of alkalinity and effect vary depending on alkali used.

Traditionally handmade method of washi uses mild alkaline wood ash, which would not damage fibre and retain the original length of kozo fibre, but it would take long time to remove the knots and scars in the fibre after alkaline cooking.
However, the traditional technique would be the least damaging to fibre, thus produce the ideal paper for preservation.

On the other hand, caustic soda is strong and aggressive alkali, and the most damaging to fibre, but it requires 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-natvie fibre or fibre for lower quality paper.

Both soda ash and slaked like is mild alkali and their chemical reaction with fibre is less damaging. Soda ash is commonly used to cook kozo, gampi and mitsumata.

Immediately after cooking, the bark is traditionally rinsed in the water to remove soluble impurities. ‘Kawazarashi’ is immersing the bark in the riever and exposing to sunlight. That would provide the bleaching effect as well as removing insoluble impurities. Such natural bleaching method is the least damaging to fibre.

Since the Meiji Period, various chemical products have become available and some bleaching agents have adopted to Japanese papermaking. The agents, such as calcium hypochlorite (bleaching powder), sodium hypochlorite, or sodium chlorite have been used in some types of washi.

When purchasing washi, it is essential to consider your purposes and refer the product information on each paper.

pH

Washi is natural between pH6.5 and 7.0. While acidic paper degrade rapidly, natural paper is suitable for long-term preservation. When judging the quality of washi, pH would be helpful to make a decision.

To select the raw materials, please use ‘search’ in the left column on the Product Page or refer to the Detailed Product Information.

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

Wooden drying boards (itaboshi) have been traditionally used for drying. The paper is brushed on the board one by one and dries under the sun slowly, avoiding shrinkage of fibres rapidly, thus requires long labour. However, the final products are resulting in soft, but strong washi, suitable for long-term preservation.

Nowadays, there are various methods. Using heated metal boards for drying have become common. Iron boards have been widely used in the past, but the possibility of iron residues oxidising and creating foxing were the problem. Use of stainless steel boards has overcome this problem. However, the texture of paper dried on stainless steel boards is somewhat stiffer due to rapid drying comparing itaboshi.

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

Machine-made washi is manufactured with a large papermaking machine in large quantity under the controlled environment. Thus, the level of quality is stable and the price is reasonable. The paper is suitable for occasions like use in large amount or the limited budget.

With handmade washi, preparation methods of the raw materials and the techniques of sheet formation vary depending on papermakers and the areas, thus each type of washi has unique characteristics. Generally handmade washi possesses soft and warm organic feeling. Therefore, searching the paper most suitable for your needs and preference from wide range of handmade washi by different papermakers in the various areas could be an adventure, but also could be a treasure hunting!
It is appropriate to select either handmade washi or machine-made washi depending on your needs and requirements.