Aoto Talk

Let's take a little break from talking Iwasaki (there's more to come) and talk about some stones.

Occasionally, straight razor users and honers talk a bit about the Japanese "Aoto." The name translates directly as "blue hone," and they do sometimes have a blue-black color, but they are also found in light grey or brown, sometimes with streaks of red. They are a "Middle stone", something like a 2000-5000 grit artificial stone, but we all know how much I dislike putting grit numbers on natural stones. Let's just say that, once you've got the damage taken out of a blade's edge, you can go to this stone and put a smoother cutting edge on.

Aoto are known in Japan as "Kings of the Kitchen Knives", and I have to say that a good Aoto can really put a heck of a cutting edge on your knives. For finer needs, like professional woodworkers' planes (Kanna in Japanese) the Aoto does an excellent job of getting an edge ready to move onto your final finishing stone. They are fast, but smooth, and are usually quite soft. I like them for what they are, a hone not usually suitable for razors (and often somewhat destructive for them)

A while back, I read a post on SRP about Aoto, that said that in opposition to Awaseto, they should be cut and finished across the grain of the stone. This really perked my interest because the three or four Aoto I've used, and the dozen or so I've perused at hone stones, have had no discernible "grain."

Every which way but loose...

I undertook to find out more about this topic, but I was hamstrung by my lack of Japanese vocabulary...I had no idea which of the several words for "grain" I found in the dictionary would apply to stones, so I wasn't even sure how to ask the several experts I had access to. Then, I lucked out.

A Japanese blogger I follow posted about refinishing an Aoto (Japanese language link, but the pictures are informative), and he happened to link to a discussion he had had, about this very issue, with Tsuchihashi-san, the owner and miner at Maruo-yama. Tsuchihashi-san mines and finishes Aoto as well, so he of course knows all about this issue.

So with this in, I can finally offer some explanation about this whole grain issue.

Let's start with a look at what kind of stones there are.

First, the most common and familiar arrangement of stones are the layered stones, usually a form of shale or slate. The layers are sometimes visible in a finished stone, sometimes not, but when one of these stones breaks, you can clearly see how the stone flakes and splits along these layers. So it is easy for the miner to tell, and in almost all cases these stones are finished along the layers. In Japanese this is called "Itame" (板目）.

Layers and flakes...yummmm

Sometimes, however, and this is what was referred to earlier in reference to Aoto, these stones are finished ACROSS the grain. This means that these layers are visible on the TOP of the stone, rather than the sides. This is called "Masame" (柾目). The reason for this difference is the hardness of the stones. Aoto tend to be very very soft, and by finishing across the grain the structure of the stone resists abrasion better, adding some "hardness" to the stone. This is also the reason that Awaseto aren't finished across the grain--this would make them entirely TOO hard, and they won't hone well.

But the problem I noticed, the lack of grain at all, comes from another phenomenon. There are some stones, including the more traditional variety of Aoto, that do not come in these layers like a stack of pancakes. They are arranged in big round clumps--and their name in Japanese is fairly apt. They're called "Potato Stones" (Imo-ishi,　芋石). These stones don't have an evident grain, and can often be used on any face. My aoto are apparently potato stones.

Which way up? You tell me...

One thing about this is, sometimes people have trouble with Aoto, thinking the stone won't hone well at all, and in this case the problem is often that the wrong face has been finished, and simply changing to the side will improve the honing experience.