Japanese Natural Stones: A Few Questions

[Luke Dupont]

Hello everyone! It's been a while.

I've been in Japan for about a year and a half now, and while I haven't had much time for woodworking yet, I've bought a few tools and sharpening stones and am keen on making time.

As I'm a fan of natural stones, I decided to try a few inexpensive Japanese Natural Stones to learn on. And, I have to say, I'm kind of impressed even with the cheap ones! However, I realized that I definitely have much to learn, which is why I'm here.

So, without further adue, a few questions / problems I've had:

1) Do I need to pre-soak Jnats?
I'm not a fan of any stone that requires presoaking, because I may want to go to a park and work, for example. It appears that my cheap stones work just fine without presoaking, though one is a bit thirsty and I have to add water intermittently.

2) Do I need to seal them?
How necessary is it to seal the sides of the stone, as I see some doing? Does this depend on the type of the stone? Do some people use their stones without sealing them?

3) Rust! Rust! Rust!
Okay, so, I've used almost exclusively oilstones in the past and avoided waterstones because I have one recurring problem: rust! Despite being careful (I think), I still often find rust developing on my blade soon after sharpening with (and wiping off the) water. Sometimes, the rust even forms while I'm still in the middle of sharpening! I try to wipe the blade off quickly and wipe it with oil afterwards, but anything made of carbon steel just seems to be very intent on rusting, sometimes even after only a few minutes of sharpening, How do you folks who use water deal with this?

Those are my three main questions; the rest, such as how much slurry or water to use / not use, I think I will get the hang of in time.

One side question though, and perhaps the most difficult thing with Jnats is knowing what is what in the first place. I haven't found a lot of good information on the different kinds of stones out there. I'm currently looking for a good but inexpensive coarse or middle stone: something capable of refreshing an edge quickly, and finely enough for coarse work or for moving straight on to a finish stone. If anyone can point me in the right direction, that would be great

[ken hatch]

Luke,

You need to get Brian to answer your questions. I'm just a JNAT dilettante but I do have a few. A Tsushima Nagura is a good set up stone and they are reasonably priced. So told me I should have a Nagura. It is fast and leaves a finish that can go directly to wood or to the finishing stone. I do not pre-soak. Mine are sealed with cashew lacquer, I haven't a clue if necessary but it is traditional and can't hurt.

ken

[Dom Campbell]

Hi Luke,

I don’t have much experience with natural stones... however try this for your rust problem:

Most water supplies have quite a bit of chlorine in them which can accumulate and cause rust. So if you can, try using distilled water (I am lucky to have a distilled water tap), and also add something like washing soda crystals to the water to adjust the water’s PH (neutralise the chlorine).

WD40 or similar as soon as your done may also help displace any water and thus prevent more rusting. After wiping this off, use your normal oil (I use camellia or 3in1) and you should be fine.


As for soaking, I think the established norm is not to soak natural stones - Odate’s book (and many others) go into some detail around this - as it can cause problems such as delamination.

Cheers,

Dom

[David Wong]

Luke,

I use Jnats, but would not characterize myself as knowledgeable. I can offer a little advise...

Most important is to never pre-soak your jnat stones. That will weaken and ruin them through de-lamination and cracking. You should always allow your jnats to dry out between uses. Make sure that the stone holder or attached stand does not hold water so the stones are not always soaking on the underside.

Sealing the sides and bottom of stones helps to protect them from becoming too wet and absorbing water internally. Sealing with paper and lacquer can also be used to strengthen a cracked stone. (See Repairing a natural water stone). I cannot tell you whether sealing is necessary. I use stones that are both sealed and unsealed. For large stones, a stand is definitely a good idea.

Coarse stones are called "arato" (rough/coarse) or "aratoshi" (rough/coarse whetstone). I have a couple of inexpensive arato - a mesuki (mud stone?), and an amakusa. The mesuki is suppose to be #200-#600, the amakusa is #400-#800. In practice, both stones are very very slow at abrading the steel on japanese tools. The abrasive particles are probably too soft and too few. I use manmade coarse stones instead. Perhaps more expensive arato may perform better.

I have a very good (expensive) Aizu stone #1500-#3000, and an Aoto #3000-#5000, that I use as my medium stones. If necessary, i'll use a arato-kun #240, Sigma Power #400, Beston #500, King #800 or Shapton Pro #2000, before Jnats.

This site has lots of info:
tomonagura.com

There are a number of good online retailers you can peruse and learn from:
japan-tool.com
thejapanstone.com
aframestokyo.com

My experience is that the more you pay, the better the stone. After a point, you get diminishing returns. You start to pay for aesthetic qualities, like color and uniformity. Not that there is anything wrong with that...

[John C Cox]

With tools rusting.. Wash your blades with hot clean water and a few drops of dish soap. Dry immediately, and wipe down with your favorite light oil.

Remember that Japan is an island nation... Surrounded by ocean.... And the natural stones are typically sedimentary... So they likely have salt dissolved into them. And that will rust your tools pretty fast. You have to wash the salt off your tools and that takes hot water with a few drops of dish soap......

Personally - Since you are in Japan... I would contact some woodworkers or knofe folks who use these there in Japan... There are probably a host of traditional practices surrounding the use of those stones.

[Luke Dupont]

Thank you all for the great advice! Especially the warning not to pre-soak my stones. There's a lot of misinformation on Jnats, it seems: I actually found information that "natural stones [referring to Jnats] should be presoaked 24 hours" on one particular website...

I picked up today a smallish (well, not huge at least) white Mikawa stone (cream and red colored) for 8,000 yen, or about $80. It seems to fit my required role of a middle stone that can do reprofiling (to some degree) and is fine enough to go straight to wood or a finish stone -- depending how fine you want to finish. The edge I get from it seems comperable to a soft Arkansas stone, but I'm sure I can get a somewhat finer edge with practice, and as I wear it in. It definitely seems to cut faster than an Arkansas, however -- and has a nice "grippy" feel with good feedback. It soaks up water quickly and tends to become dry, however.

Thank you for all the advice! I'll try employing some of it in regards to rust. I'm sure that it is also partially about forming the right habits: it occurred to me that, perhaps since I've not had to worry about rust with oilstones, I may be more careless than I realize when it comes to quickly wiping off and oiling my blades. I'll pay special attention to it and try some of the recommended techniques here; hot water and soap are interesting suggestions!
I'm keen to learn more about Japanese stones, tools, and how to use and care for them, being that I'm here and have access to them (and potentially, people knowledgeable of them!) now.