I have not seen this documented anywhere, so I thought I would throw some pictures up for for reference...
My japanese natural waterstone had developed some pretty serious layering cracks. This was probably my fault for not mounting the stone to a permanent base. I read mentioned that a method of repair and support for cracked stones is to use japanese lacquer (urashi), and layers of a persimmon soaked paper (yoshino-gami shibu-tsuki). So when my wife was traveling in Japan, I asked her to order some cashew lacquer and paper from a sword supply store Namikawa Heibei Co., Ltd. Cashew lacquer is reportedly far less toxic and faster drying than regular urashi lacquer, though there is a caution that some people report having serious allergic reactions. The paper description says that the persimmon tannins make the paper stronger.
I waited until the first 100+ degree day, since urashi is normally cured in hot humid environments. Cashew lacquer has the consistency of molasses. I used an acid brush to paint it onto the outer surface of the stone. I then pressed on a strip of paper. The paper strip was not long enough to cover the entire stone, so I brushed on another coat of lacquer and pressed on another strip of paper to fully cover the stone. The stone then received another coat of lacquer. Finally, I coated the bottom of the stone and folded the paper down.
After a few days to let the lacquer dry, I made a base of hardwood and hot-glued the stone to the base. I have been using the stone for a couple of weeks now and the repair seems to be holding up well.
David
DSCF3782.jpgDSCF3786.jpgDSCF3787.jpgDSCF3788.jpgDSCF3789.jpgDSCF3792.jpgDSCF3799.jpg