Aoto was the first stone was the very first Japanese whetstone I have ever had. I got it mainly as an experiment in 02/2009. As far as my sharpening needs went, I didn't really need a new stone or a sharpener at all. I've already had full range of various grit sharpeners to handle any sharpening job. Starting from 120 grit DMT 8XXC Diamond Benchstone and ending with microabrasive films and 0.25µm Diamond Crystal spray for the highest polished fine edges. Plus an array of leather strops or hones. On top of all that, I had several synthetic whetstones. Still, I wanted to try the real thing :) Takeshi, at Aframes Tokyo had a few of those to choose form. After exchanging several emails regarding the options I had, I've picked this one.
General- Aoto stone was mined in famous Kyoto mines, namely in Tanba region. The highest quality whetstones are mined in Japan, the best, and the most expensive of them are around Kyoto. At this time, I am still not very clear with the whole classification of the Japanese natural whetstones. This particular stone is Nakato class, in other words it is medium grit stone. It was my first stone, so I could've picked anything. As far as I understand now, natural whetstones of very low grit, or very coarse grit in other words are not durable and get worn out quickly. The highest grit stones are very expensive, even the broken pieces can cost several hundred dollars easily. I have a 12000 grit Kitayama stone, which is synthetic, but still getting the same grit on the first natural stone wasn't worth it. After all I wasn't sure, if I would like natural whetstones at all. Good thing was, Takeshi has very generous return policy and if I didn't like it, I could return the stone at no charge. The only condition was not to have damaged the stone, which is easy, unless you drop it, or abuse it otherwise, just sharpening on it few times won't cause any serious degradation.
Stone itself is in pretty good shape. Exact dimensions are 200mm×60mm×58mm. It's not the perfect shape, corners are chipped off and there's a crack on the surface, which can be seen on the linked image at the beginning. However, there was nothing on it that could affect its sharpening performance. Just to be on the safe side, I've flattened the sharpening surface with DMT 8XXC diamond stone. One good use for 8XXC, besides cutting initial bevels on very stubborn steels. All that took about 3 minutes tops. The Aoto stone was ready to go.
Performance- To get the Aoto stone working it needs to be soaked in a water for about half an hour. May be a little less. Compared to normal sharpening stones that's a long preparation time, but that is the nature of the beast. On the other hand they cut much faster and smoother. Besides initial soaking the stone needs periodical watering during the sharpening process. All that makes the process rather messy, but nothing unmanageable. So, after soaking it in tap water for 30 minutes I took it out and proceeded with sharpening. The knife I chose that day was Kobayashi Suminagashi Nakiri. Originally it had 15° angle per side and once I was sure about its performance I've decided to lower it to around 7°-8° per side. Obviously, I didn't start cutting new bevel with 2K stone. Initial steps included Bester 500 grit stone, to cut the new bevel, and Bester 700 grit stone to remove scratches left by previous stone and refine the edge. Now was the Aoto's turn. First thing I've noticed after taking it out of the water how soft and slippery the stone felt. Nothing like synthetic ceramic stones I have used so far. Sharpening itself, on Aoto is much more pleasant experience compared to synthetic stones. Cutting speed is very high for the stone of that grit, which is in the range of 2000-3000. As far as I can tell, natural whetstones don't really have precise grit number, it's the range most of the time. Range or not, it cut very fast. It took me less than 10 minutes per side raise the burr and polish the edge. Amount of water that I had to use was more than twice less compared to 500 and 700 grit Besters. Those two(Besters) are more like sponges, to be honest. Why this is important? Because you don't really want to get interrupted during sharpening. Having to spray water on the stone once in a while, is an interruption and distraction. I really appreciated Aoto stone ability to hold water so well.
One more curious thing I have noticed. generally, the more mud you have on the, stone the faster is its cutting speed. Mud on the stone is a mix of stone and metal particles with water. On Aoto it was possible to control the polish of the edge by reducing the amount of the mud. As far as I understand now, mud of Aoto eventually breaks down into finer particles and you get not only better cutting speed, but also finer grit, closer to 5000-6000. Which is that I've felt based on final sharpness, see below. Either way, the final result was nicely polished edge, that could whittle hair. I've never achieved this result before with such a low grit. As usual I'd have to take the edge over 6000 grit to start whittling hair. Very, very nice result and I love this stone now.
Conclusions- Well, only positive conclusions. I don't want to generalize based ona single stone, but common knowledge is that natural whetstones hold water better. Which, is an important feature. Second, the feel of the stone does matter. It's not about having fun while sharpening, although nothing wrong with that, just the whole hand sharpening process is based on tactile feedback and having a good one is important. You'll get more precise and accurate edge in the end. That's my theory :) In simple words, natural whetstones, or for now, let's say Aoto stone is easier to use, cuts faster and provides more refined edge than other stones of identical grit. Sharpening is less disruptive due to the stone ability to hold more water compared to synthetic whetstones. I'm definitely going to buy high grit whetstone, that's gonna cost me, but on the other hand I sharpen all of my kitchen knives to very high finishes and it'll be very useful for my sharpening needs.
Last updated - 09/01/11