About This Item
Mikawa Shiro Nagura 1lb. 7.2oz. (655.6g) Japanese Natural Sharpening Stone
I am not sure which layer of Mikawa shiro nagura, but it looks medium to medium-high grit. It looks lower side class in Mikawa shiro nagura.
It raises great amount of black color slurry quickly.
(Scale; 1 to 10, 1-3 is very soft muddy rough grit whetstone 3-6 is soft medium grit whetstone, 6-8 is hard medium grit whetstone; 8-10 is fine grit whetstone)
It makes my blue II steel kasumi blade knife Hagane became frost silver color finish. Jigae became little darker frosted silver color finish.
(Scale; 1 to 10, 1-3 give deep scratch marks to the steel, 3-5 is delete the 1-3 scratches, 5-8 makes the steel cloudy, 8-10 makes the steel semi-mirror finish or mirror finish)
According to Dr. Kuniichi Tawara who is a Metallurgy doctor, and very famous Japanese sword researcher, Koma molecule is 10 to 20 micron. It might be like Botan or Atsu (Chu-nagura) class grit. It should be good for one or two stones before starting the fine grit sharpening.
For razor sharpening, it is used one or two before the process sharpening by fine grit whetstone like Nakayama, Ozuku, Wakasa, etc.