Repairing a natural waterstone

[David Wong]

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. (http://www.namikawa-ltd.co.jp/english/index.html) 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

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[David Weaver]

Looks nice, David. I'm trying to place where I've seen a stone like that before, I think a couple of the LV stones I got a while ago (they're long gone now) had that color and surface tone, but I don't know where they came from (like what mine) because they just had an imanishi brand stamp.

Is it possibly a hiderayama mine stone?

[David Wong]

David,

You have a good memory. It is the Ohira Kozan stone that I purchased from you a couple of years ago. I really like this stone and use it as a final polisher. It cuts very quickly and leaves a nice edge for me on japanese chisels and plane blades. The only other natural stone I have is a hard Aoto, and the Ohira Kozan is much nicer.

[David Weaver]

Yeah, I got that stone from hida. I thought it was darker than the pictures, but cameras do funny things with color. I recall that being a very even stone that cut pretty fast on slurry but left a nice edge on clear water. Some of the super super hard and fine stones I have aren't as useful for anything but razors, and even then, they have to have something else finish the edge for them to step up to it.

I certainly had no idea it would delaminate!!! there are a lot of those out there - they were sold by misugi designs before hida got them, and when the woman from misugi designs went back to japan (I think to care for her father), Hida took all of the stock. I don't know how much is still coming out of ohira (it might be closed), but not ozuku and shoubu seem to be the mines of high volume, both of them putting out a lot of green stones in the case of the fine ones, super super hard stones.

Several people have told me that if I don't lacquer the sides of my stones, they may delaminate, but I didn't believe them.

[Jack Curtis]

Kayoko returned to Japan to care for Yataiki as well as her mother.