As a paper conservator, I spend a lot of time in the lab examining and treating Asian paintings and prints, but another part of my job is to ensure that the art on display is also being properly preserved. With the opening of the new Roger L. and Pamela Weston Wing and Japanese Art Galleries, this recently took the form of researching and testing a traditional Japanese material that was used in a display case.
The tokonoma case (top image), which was designed to exhibit paintings, bowls, and other utensils used in the Japanese tea ceremony, closely replicates architectural elements seen in Japanese teahouses. One of these elements is the tokobashira, a pillar made from a naked tree trunk. Our pillar is made of Japanese cypress—for another example of this wood, visit Hinoki (see above), the giant sculpture by Charles Ray in gallery 292 of the Modern Wing—and it was imported from Japan. However, when it arrived in the USA it did not match the darker woods seen throughout the other Japanese art galleries. Everyone wanted it to be darker, so the architects proposed using kakishibu, a traditional Japanese material to stain the wood.
I knew a little bit about kakishibu. It is a brown liquid composed exclusively of fermented persimmon tannin and water. Today only a few traditional craftsmen use kakishibu, but it was once commonly used as an insect deterrent on wood, or as a way to strengthen and waterproof paper and textiles. The museum has several kakishibu impregnated paper stencils (see above), which were used in dying kimono silk.
Unfortunately not much is known about the chemical properties of kakishibu, and I was worried that—even when dry to the touch—off-gas chemicals could cause the deterioration of paintings and other artwork on display in the case. So I began to research kakishibu. From written sources, I learned that it becomes darker as it dries and when dry it will darken further if exposed to full spectrum light. I concluded that the pillar would have to be coated and allowed to dry for a few weeks before it could be installed. Also, liquid kakishibu will become black or purple if it is exposed to iron, so nails and other metal fixtures would have to be added after the pillar was stained. Of course, this wasn’t a worry because traditional Japanese building techniques don’t use nails or screws. In addition, I spoke to colleagues in the Asian art conservation field. Everyone complained of the odor of the liquid and as far as I could discover, no other museum has used kakishibu stained wood in an exhibition case. Since I still had some doubts about kakishibu, I decided to test it.
To prepare for testing, I coated glass microscope slides with the kakishibu and allowed them to dry for several days. I can report that liquid kakishibu smells like stinky feet, and the odor lingers for days, but as the liquid dries it turns into a tough impermeable film that is almost impossible to wash off. It also changes from beige to a warm reddish brown color. Next, I did the Oddy test. Oddy testing is simple to do and easy to interpret. The material in question is placed in a jar with strips of lead, copper and silver foil (see above). We use these specific metals because they are indicative of corrosive vapors off-gassing from the material under investigation, which, in turn , could be detrimental to artworks (like paintings or bronzes) that come in close contact with the tested material. Then a little bit of water is added, the jar is capped so that it is air tight, and it is locked in a warm oven. After about 12 weeks the jar is removed and the metal foils are examined. If the metals are tarnished or corroded, the conservator recommends that the material not be used. If the metal retains its shine, the material is approved for use.
The kakishibu passed the Oddy test, and the museum hired a Japanese craftsman to stain the tokobashira. I hope to live to be a very old woman so that I can see how dark it becomes over the next 50 years.