"Posterity, you will never know how much it cost the present generation to preserve your
freedom. I hope you will make good use of it. If you do not, I shall repent in heaven that ever I
took half the pains to preserve it."
Hakka Tomae Japanese Natural Stone finish compared to synthetic stone finish
In this video I demonstrate the Hakka Tomae, a stone available in limited quantities at Chefknivestogo.com These stones are imported by me (Precise Sharpening) for Chefknivestogo and are stamped (on the back of the stone in this instance) with the Tanaka Toishi Kyogyosho stamp, assuring you of a quality and authentic product.
The mine it comes from is the Hakka mine and the particular layer is the Tomae layer, a more uniform and less stratified layer than the suita layer.
Because the stone comes from a mine and layer I am familiar with I already know the characteristics of this stone even before using it. You will hear comments to the contrary that each stone is a complete mystery grab bag. I describe the stones characteristics before use and, of little suprise to me it performs as expected.
It absorbs water somewhat slowly, although adding more water from time to time is necessary. It is a muddy stone, unlike many other polishing stones, so it is particularly suited to single bevel knives like yanagis or usubas that require a refined edge and don't usually have a perfectly uniform front bevel. It is also well suited to double bevel knives like this Moritaka that has been ground to a zero grind - with no separate bevel but just the two sides of the knife meeting with just a slightly convex grind - not quite a full traditional hamaguri grind.
With continued sharpening, a continually refined mud is being built. I look at the edge as the process continues and a natural stone finish gradually replaces the initial synthetic stone finish, providing a contrast between the softer cladding steel (jigane) and the harder core steel or hagane, with the softer cladding producing a softer sand blasted hazy finish and the harder steel showing a type of mirror finish much like an antique mirror with a black haze. This is referred to as a kurobikari finish.
Eamon, the purpose of this video was to simply demonstrate contrast what one sees with a natural vs synthetic stone finish. Since it is a polishing stone it takes off very little metal. The entire knife will be redone at a coarser grit to correct some of the minor problems that you note. In this instance the natural stone finish simply provided a more exaggerated view of these inconsistencies, of value in it's own right.
I should also note that the Moritaka knives are hand forged. I know you are not a fan of these knives, and have commented on this elsewhere, but please understand that hand forging does not produce the same level of surface consistency that you get from grinding out stamped out knives. Nor should it. It is a far more difficult process requiring far more skill to produce. Even so, with the less than cosmetically perfect finish on this video, it still cuts extremely well. I'm uploading a subsequent video that will better demonstrate the stone rather than just the natural vs synthetic contrast. In this video I actually do correct these issues.
Yeah, I didn't even notice that it was a Moritaka for a while! THAT'S a whole 'nother topic.
The real thing I was wondering was if it was like that because there is an overgrind or if it was pressure-related--I noticed your fingers were never over that exact spot, so I've got no way of knowing if it was the abnormality was inherent in the knife or brought out by the stone, you know what I mean?
Well if an area is lower than the surrounding area, this is exactly the area that DOESN'T require pressure. You need to lower the surrounding area to the level on the lowest point to approach a more coplanar surface. Assuming that pressing on the hollow areas distributes the force around the hollow or lower areas is a flawed approach or at least less optimal approach, especially at the two ends of the knife (IMO).
In the first video I demonstrated the difference between a synthetic stone finish and a natural stone finish. To those that closely observed the finish some coarser scratches were observable. Some have mistaken these scratches as being from the Hakka Tomae. I would remind you that this is not a coarse stone but rather a polishing stone that neither can remove such coarse scratches nor cause them.
So I went back, going back as coarse as a 400 grit stone up to a 2000 grit stone to remove the majority of these scratches and redid the finish with the Hakka Tomae once again, this time more fully demonstrating the capabilities of the stone itself.
In this video I finish the final stages to demonstrate the Hakka finish without the distracting coarser synthetic stone finishes.
Between your video and response, I got my question answered.
I think that by attempting to be succinct, I came off as implying something. I was just trying to do some deducing regarding the aggressiveness of the stone, not really a question of technique or whether that grind is a good or bad idea.
Leigh, typically the Moritakas come with a convex grind - ground convex on both sides. This grind is a bit more acute, something that the steel that Moritaka uses - in their hands - is fully capable of handling.