Monday, October 02, 2023

Papermaking Process

Preparation of the Fibers


Harvesting the Bast Fiber

The KOZO is harvested during early winter (November to December) after the leaves drop. The stalks are cut into 1.2 meter (about 4 foot length) and cook in the special barrel shaped steamers. After they cooked, the bark is striped from the bottom of branch to the top. The stripped bark are tied to small bundles and dried. Those barks are stored or processed to white bark in spring.

Preparation of the Fibers 1

The dried strips of bark are soaked overnight to soften the tissues and makes the removal of the outer layers easier. The soften barks are rubbed between feet in running water to remove dark outer bark. The bark is consisted of three parts; black bark, green bark and white bark. Some papers like Kasu-gami contains black bark purposely, but commonly high quality paper are consisted of white bark only and does not contain balk and green barks.

Preparation of the Fibers 2

Once the dark outer layer is removed, the green layer, which contains more hemicellulose than the pure white layer, is carefully scraped away with a knife. The buds, gnarls and flaws of branch are changed their colors to dark brown. These are carefully removed without damaging the fiber. The cleaned bark (white bark) is dried in a cool shaded area until ready for further processing.


The white bark is soaked overnight before cooking. This re-hydrates the dry bark and helps to remove any water-soluble elements and makes it easier for the alkaline solution to penetrate the fibers. This bark is again rinsed to remove any loose bits of rubbish before cooking. The prepared bark is cooked in an alkaline solution. Traditionally, wood ash [K2CO3 or potash] was used. Nowadays, caustic soda [NaOH], soda ash [Na2CO3] or slaked limes [Ca(OH)2] are used depend on purposes. The amount of slaked lime used is about 20%, soda ash is about 18% and 15% for caustic soda for the dry weight of the fiber to be cooked. The amount of water is equal to at least 10 times the weight of the dry fiber. It should be enough if the bark is completely soaked in the water. Until water is started boiling, keep the fire to high. Once it started boiling, keep the water temperature lower, to not flow the water from the pot. After 30 minutes from boiling, the fiber becomes soft and the liquid turns a dark brown as the non-cellulose materials are dissolved during the cooking process. The fibers are stirred occasionally to prevent scorching and to insure an even cook. The characteristic of washi is determined by the amount of non-cellulose materials contained in the fibers. When a strong alkali is used, more of the non-cellulose materials are dissolved resulting in a softer paper. If more non-cellulose materials remain in the fiber, then the paper has more body. The type of alkali used also affects the color and feel of the paper. Depends on the purpose of the paper, the amount and type of alkali are adjusted. The fiber is tested after about two hours. If it can be gently spread apart to reveal a fine network of fibers or if it can be pulled apart widthwise easily, then it is sufficiently cooked. When testing the fiber, it may be better to choose a thick piece of bark and carefully removed and rinsed to cool.


When the bark is cooked, scum will be appeared on the surface of the cooking liquid. After the heat is turned off, the cooked fiber is allowed to soak into water to remove the scum and non-fiber material which was eluted by alkaline solution. The next day, the cooked bark is thoroughly rinsed in water. In the case of cleaning KOZO bark, since it is difficult to clean up with machines, this process has to be done by hand. Put a basket in water and put small amount of bark into the basket, then the bark started to clean. At this process, the purpose of cleaning is to remove scars, buds, unevenly cooked parts and discolored parts. Since the bark is already eluted, the bark is easy to tear apart. To keep the quality of fiber, the bark must be carefully cleaned and should not be ripped as much as possible. If white paper is to be made, the fiber are bleached before this cleaning stage. Generally, chlorine based solutions are used; however, natural methods which bleached by running water (KAWASU KAWASARASHI) or snow (YUKISU YUKISARASHI) are sometimes used.


The cleaned strips of bark are now ready for beating. The beating is done on a wooden or stone surface with a beating stick. The separate strips of bark are beaten until it becomes a mass of separated fibers. Now much of the beating is done by automated stampers or NAGINATA beaters. The beating process helps the fibers to separate in the water.

Basic Papermaking Process

NAGASHIZUKI method is formed by three basic actions of papermaking process, 'KAKENAGASHI'. 'CHOSHI' and 'SUTEMIZU'. First, scoop up relatively small amount of the fibers and move the mould quickly to place the fibers on the surface evenly. The quick movement prevents attaching dust on the surface of the paper. This action creates the surface of the paper, and it is called 'KAKENAGASHI' or 'HATSUMIZU'. The next action is called 'CHOSHI'. Scoop up the fiber more than the first time, and move the mould to twine the each fiber. Until it became wanted thickness, continue this action. Utilize the elasticity of the bamboo, which is placed as overhead suspension system, and adjust the amount of fiber to scoop up and move the mould evenly. Depending on the region and the kind of paper to make, the movement of the mould is different. When the paper is made, remove the screen from the mould and place the wet paper on the SHITOITA, couching stand, with dried paper or cloth on and JOGI, guides, is attached on the stand. At this time, carefully lowered the screen to place the wet paper on the SHITOITA to prevent trapping any air between the sheets. To remove the screen, it is lifted starting from the edge nearest the papermaker, then peeled off away from the papermaker.

TAMEZUKI is the method which has been taken from old time, and the material which is short, well beaten and does not contain ÒNERIÓ, is used in order to spread the fiber in water. Well beaten material makes possible to create appropriate thickness with one scoop of fiber. Nowadays, papers which take TAMEZUKI method are used as postcard and paper for school diploma. However, for these papers, since the material for NAGASHIZUKI is used which beating is not applied as much as the material for TAMEZUKI, 'NERI' is added in order to slower the flow of water on the screen. When these papers are dried, another dried paper is placed between the just-made wet papers or press immediately and dry by placing on a flat board. (See making postcards by TAMEZUKI method)



Leave the post of newly made papers (it is called SHITO) for overnight to drain the water naturally. The next day, place the wet papers between two bigger sized boards, and then press with a compressor to remove moisture. The weight is gradually added for nearly 6 hours. By pressing firmly, paper has rigidity. After pressing paper, the paper should contain approximately70% of moisture.


The pressed papers are carefully removed one by one from the post and brushed onto wooden boards to dry naturally or onto mechanical dryer, steam heated metal surfaces. The wooden boards of pine tree, horse chestnut and Japanese cypress are used as drying boards. The best lumber for drying board is gingko tree since it has smooth surface and large surface area. When remove the wet paper from the post, peel off by keeping the paper parallel to the post. Then the peeled wet paper is placed onto the dryer and brushed on it. The drying method, natural (ITABOSHI) and mechanical (JOKI KANSOKI), affects the finished paper. Especially, when thick paper is dried by mechanical dryer, the surface of the paper tends to become fluffy and over dried. The finished papers may be treated with DOSA ( a sizing to prevent ink bleeding), KONNYAKU ( a starch derived sizing for wet strength) or KAKISHIBU ( persimmon tannin). It may also be dyed with chemical or natural dyes or textured to make paper like MOMIGAMI ( a randomly crumpled paper) or CHIRIMEN ( a crepe textured paper).