Nikawa is made from the skins, bones, tendons and intestines of animals or fish skins and bones, which are boiled in water to extract gelatin. This is the Japanese version of natural glue and is primarily available in a solid form – a pack of sticks (traditional), beads, or a block. As with many other natural glue types previously discussed, it must be heated up to liquefy and use for binding and adhesion.
Here is a recipe for Sizing Japanese. The Nikawa glue strengthens the paper, constricting the fibers, the addition of alum that is combined with the glue make it less absorbent:
1. Place beads or cut the Nikawa stick into tiny pieces and place into a qt. container. Add 200cc (approx. 1 cup) of water. Soak at least 6 hours or overnight.
2. Heat the Nikawa mixture on low heat, mixing constantly to dissolve Nikawa pieces, making sure it does NOT boil, until it melts away and the color is light brown.
3. Pour Mixture into a large bucket, add an additional 4 cups of water.
4. Add about 1/8 teaspoon of Myoban (Alum) into the mixture and mix well until Myoban dissolves. Now you have the Dosa mixture and it is ready to be applied to the paper.
5. Dip the brush into the mixture and tap the brush to remove excess.
6. Brush on both sides of the paper slowly and evenly from side to side in the same direction. If you want a stronger sizing, you can repeat this process two or three times. Allow to dry after each application.
Let this dry completely and follow same instructions for other side. Do not use a blow dryer or fan.
Here is a supplier link for information and the use of Myoban/Alum http://store.hiromipaper.com/myobansizingdosa.aspx
A collection of Japanese sizing recipes can be found at http://blog.sina.com.cn/s/blog_67f3838b0102vedi.html . It is a Japanese blog published by Idaoy with fabulous information and illustrations of his process. He lists the ingredients and processes for various historic sizing recipes. Here are the
1926 ingredients by Mr. Urushibara’s recipe (in “The Technique of the Color Woodcut by Walter Phillips, 1926) to make enough Dosa to size 14 sheets of paper: 1/8 oz. Alum, ¼ oz (gelatin/nikawa), and 35 oz. water.