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Natural Aoto in professional use?

Sat Jun 08, 2013 9:00 pm

I have a beautiful Monzen Aoto stone I purchased for the sole purpose of using, the only problem is it takes almost 30 minute of soaking before its able to be used. Now that's not so much of a issue in a home setting but in a professional setting I'm finished sharpening a whole set of knives in 30 minutes.

So here's the BIG question. Because I would be using it so much do you thing a permanent soak would work? Or end up killing the stone?

Re: Natural Aoto in professional use?

Sun Jun 09, 2013 1:15 pm

Well JB, we're all waiting to hear from Ken on this one. It would be helpful to know what lower to mid grit Jnats could be soaked full time. For those of us using our stones every day, it's so much nicer being able to leave them in the bucket and employ them at a moment's notice. All my Nubatamas having been living underwater now for months, from 150 grit all the way up to 5K, with absolutely no issues whatsoever. There's gotta be some Jnats out there that can handle the H2O.

I've been considering that Monzen now for some time, so it will be interesting to hear some responses here. In the mean time, my 1200 nubatama is getting the job done.


Re: Natural Aoto in professional use?

Sun Jun 09, 2013 3:09 pm

Same with my Nubatama's, I have a feeling the Monzen would be fine but part of me doesn't want to be the test subject that finds out the hard way.

Re: Natural Aoto in professional use?

Sun Jun 09, 2013 6:53 pm

Well I'm not a big fan of perm soaking or especially soaking stones in the same water with others, so I don't really have much experience with this. I have a call into Japan for a definitive answer regarding Monzen, Aoto in general etc. Until then I would be cautious.

When I use Aoto or Monzen I don't soak but just wet the surface, adding water as necessary. I may just let the mud dry and start with broken in mud if I don't need the aggression or just want to start at a finer finish. This is fine with regular use, but leaving mud used on knives for longer periods can cause rust to develop in the mud. Using this technique, I'm up and running in just a few minutes.


Re: Natural Aoto in professional use?

Sun Jun 09, 2013 7:15 pm

The only problem with not soaking is the monzen drinks like a sponge and without soaking does not work the same.

Ken, if you could get a solid answer from your sources that would be awesome. So far its had some 8 hour shifts in water so I might just permanence soak it starting Monday.

Re: Natural Aoto in professional use?

Mon Jun 10, 2013 11:20 am


Warning! If your going to soak a Aoto only soak for the period needed OR LEAVE IT IN THE WATER!!!!

My monzen now has a crack down the center from end to end. (I left it out to dry and that was a bad choice)

Re: Natural Aoto in professional use?

Mon Jun 10, 2013 1:15 pm

Well, as you might suspect by now, they don't recommend permanently soaking natural stones in water. I also specifically asked about Aoto and Monzen . They also don't recommend soaking various stones in the same container either. They make the additional suggestion of covering the stone with a damp cloth, presumably to allow the stones to dry even more gradually.

Now, being conservative they don't recommend permasoaking [natural or synthetic] stones in general, however a number of customers seem to have had good results with the Nubatamas permasoaking, so I would say in general to do this at your own risk. I would emphasize that the 4k and 6k Ume should most emphatically not permasoak as they have a similar formulation to the Chocera / superstones which should also not be permasoaked.

Jason, at this point, I would make two suggestions -

1. lacquer the stone - I can give you details.
2. Mount it to a base. Wood is traditional, but I have used a glass plate for my own use. The wood may warp over time if left soaking - again not recommended..

Both of these reinforce the stone, reducing the possibility of further crack expansion. I would suggest lacquering with structural reinforcement in the lacquer. I did this on the Tajima stone I used in the video, which broke during shipment.

Many natural stones have a grain to them. You can often see this in a more subtle way on aoto, in an obvious way with Amakusa. You also see this somewhat obviously with the layers of many suita, but can also see it in tomae stones too. Splits usually do show along these lines, and I have had to deal with this when cutting stone too.

The water can exacerbate these natural fault lines, which can be internal and not obvious at the surface. Obviously if a wet stone freezes or is exposed to direct sunlight the water pressure can split stones (nats or synthetics). For this and other reasons, Tanaka-san won't ship stones until they are completely dry. The problem is essentially the same with wood which can split or check in a similar way.

I would also not wait to reinforce the stone and do it ASAP. Let me know if you need some help with this or want me to do it.


Re: Natural Aoto in professional use?

Mon Jun 10, 2013 8:46 pm

I realized a few things today, first was that low humidity is not helping my situation. My stone was robbed of so much water so fast I would bet money on it being the reason for the cracks appearing. The wet towel idea probably would have saved it from cracking.

Being 110+ degrees recently is increasing water evaporation to the point our jar of water in the grinding room for dipping blades was missing 2 inches of water :o its a cooled building but that doesn't make up for the low humidity.

So after seeing that today I realized it would be better to just leave it in water permanently. Actually, putting it back into the tub made the cracks close up and not affect stone performance.

I know long term soaking is not exactly recommended but in my experience it only benefits the stone to do so and I gotta go with my gut on this one. I agree some stones should not be soaked long term but others, well, I can't deny the last few years of my stones being under water.

Re: Natural Aoto in professional use?

Tue Jun 11, 2013 12:34 am

Jason, it's a datapoint I otherwise wouldn't get :) So while I can't recommend it, I understand your motivation for doing it. Let me know how this works out for you. Also if you want to reinforce the stone anyhow (recommended), let me know and I can go over what you might want to do.

It doesn't surprise me that the cracks close and open a bit with rehydration. That wet towel idea may be helpful. Next step might be to keep them in a humidor or wine cooler :) Yes, I'm kidding or I think I'm kidding.


Re: Natural Aoto in professional use?

Thu Jun 13, 2013 11:54 pm


If you are after a mid grit natural that is more or less splash and go and the one you have is not working out, may I suggest an Aoto Aono.

I got one of these guys from Ken to replace my Bestor 1.2k when I feel the need to go Natural, and its been really just great. I splash some water on it, hit it with the slurry stone, and in only a few seconds, its ready to.

Just a thought.
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