I'm taking this whole Japanese shaving thing to heart, learning as much as I can about all that I can, and it's really getting interesting...To me, at least.
People who are familiar with Japanese hones will have heard the word "Nagura" before. Those who haven't, well, basically when you use a natural Japanese stone to sharpen things, very often it will have a smaller stone with it that you rub all over the surface of the hone to make a thin mix of water and grit rubbed off that smaller stone. The smaller one is called a "Nagura". This is used in traditional Japanese honing to help increase the range of a hone's effect--often, a hone with a nagura will polish faster and more smoothly than just a hone itself. Why? I don't know. But I plan to find out.
Now, here's the thing that got me going on this--people dealing with straight razor honing have started using this word to describe ANY stone you use to make a slurry paste on your hones, and so we get things like "Cotigura", a portmanteau of "Coticule", the Belgian wonderstone, and "Nagura". Or people call the DMT card they use to raise a slurry on their stones a Nagura...Even Japan isn't immune to it--every little stone included with the synthetic water stones are called Nagura, as well. So I used to think that the word just meant "slurry stone", until one day in a thread on SRP where I posted videos of me honing on a Japanese natural stone using a slurry, someone asked me "Is that stone a Nagura or a Nakayama?" That question threw me. As if, Nagura must mean something much more than I had thought.
I was really confused...and then I started thinking about the name "Nagura." It doesn't have a meaning, or not at least one that is related to what it does. The kanji for the name, 名倉, has NOTHING to do with stones, or polishing or honing. Which is odd--Japanese is usually a pretty pragmatic language when it comes to objects. The word for a hone, 砥石 (to-ishi) translates directly to "polish stone". (Or, an example I like much better, the word for honey 蜂蜜, "hachimitsu", is "bee syrup".) But Nagura? Roughly, it means something like "Famous Storehouse". That looks less like an object name, and more like a PERSON name.
Which led me on a merry chase...
I started with a simple search on the term. 95% of the hits on Google were for people. Hmmm...
Then came the motherlode. There is a seller on the Japanese Yahoo Auction site that keeps listing Japanese hones and Nagura, and they happen to have a webshop, which happens to include the word "nagura" in the URL. I investigated, and these guys take Nagura SERIOUSLY. They have pages and pages about them, and this stuff is amazing. So I started studying.
Nagura, as it turns out, are essentially super-fine hones. Due to reasons like highly variable hardness, size and immense rarity (read price), are not suitable for making actual hones. Instead, they are broken into small pieces and used with the hones from more suitable sources (like the Maruka Nakayama mine in Kyoto). And like the Nakayama mine, there is really only one serious place to get a Nagura.
According to the late Kousuke Iwasaki, when he first started making razors he had trouble with honing. he was getting breaks and chips on his edges, which he eventually found came from the inferior nagura that were being sold by the merchants--they were cheap, and easily found, and of substandard quality. So he began searching for a long lost source for the Nagura that had bene sued for centuries in the polishing of Katana...He took this selection very seriously; in his book "刃物の見方" ("Understanding Bladed Implements"), he said something along the lines of "If a razor maker can not hone a razor well, the razor will not shave well, and people will think that the razor is no good." So he worked on researching just where the best hones, and the best nagura to use with them, could be found.
The Junmikawashiro mine (純三河白-I'm not at all sure of that reading) in Aichi prefecture is the only place in Japan that produced the Nagura that Iwasaki-san found suitable for the finest honing and polishing. Not only that, he identified the different seams of the mine, and with the help of geologist Nagayuki Asano divided them based on their polishing effects, speed, and purity.
The ten seams of the mine are shown abov, in a page from Iwasaki's notebook.
They are:
1. Mejiro (White-eye)
2. Tenjou (heaven)
3. Buchikou
4. Koma (very fine)
5. Botan （Tree Peony)
6. Layered Botan
7. Mushi (nothing)
8. Atsu (？？）
9. Ban （？？）
10. Shikiban.
I personally am still learning the differences between these seams. I know that the Koma and the Mejiro are supposed to be the finest, with Tenjou next, while the Botan is fine and fast cutting...
So I bought one of each!!!! (Well, no Koma...yet...)
I'm going to keep studying these, and I hope soon not only to have a better grasp of WHY you need them, but how to use them and the differences between the three types. But what I fear, and what will truly be something to look out for, is...
Nagura Acqusition Disorder.
Oh dear...
