Kin Shirushi Narutaki Asagi

The Mustard Brick


Let’s address the elephant in the room: “How is a stone that vibrant, mustard yellow an Asagi and not a kiita?”

It’s a matter of typicity and other colours present on the stone. And it’s also a numbers game –  Kiita (meaning yellow plate)  and tamagoiro (meaning egg colour) are way less common than people think but often used in connection with just about any slightly yellow stone because they are so sought after.  In terms of typicity, kiita is often, but not always, slightly softer.  And perhaps the most revealing is the side on view and bottom view of this stone which shows a truly remarkable split personality.

Asagi Town
The transition


So, we’ve been introduced and we know more-or-less who our dance partner is, but how does she dance?  Friability is not an adjective one can use with this stone.  It is relentlessly unyielding of its own particles, but that’s not to say it’s doing nothing while being rubbed.  When one is establishing an initial polish and scratch pattern with this stone (and many other hard stones) it benefits from lapping with a diamond plate. At a microscopic and fractal level, this exposes a lot more surface area of stone per unit area of knife area being pressed into it.  But this phenomenon can only be taken advantage of by having enough, considerable, downward pressure applied on your recently roughed-up surface. What you’ll find is a black inky suspension on the stone

Freshly lapped with lots of pressure applied

What i find with a technique such as this is a darkening of the resulting finish on clad, san mai knives which I posit has something to with scratch depth and light reflection.  What this technique also does in my novice hands, is make the finish more susceptible to variation in the form of scuffs and streaks, a steadier hand than mine might not have this problem.  The other caveat with this technique, and harder stones generally, is that when a lot of pressure is being applied to a stone, you’re far more likely to dislodge scratchies.  That is, stray particles that strafe the cladding but generally leave the core unmolested.  Below is a quick edit of the more pressure-heavy part of a sharpening kata.

This then brings us to a second polishing sequence and technique whereby we take full advantage of the stone’s hardness and fineness.  With this technique one smooths out the surface as much as possible with a tomonagura and then buff over the surface of the stone with way more water than would be used in the first technique and a far softer, more gliding motion.

Kin Shirushi Doi polish

Although a far more subtle process, the stone all but roars into life at this point and warrants the (not inconsiderable) price of admission.  Things start to shine like crazy and get very, very sharp. It excels on harder steels with finer grains and I have enjoyed some spooky edges on Doi; Kato; and both Bloodroot and Comet Knives’ flavour of 52100, both of which seem to be exceptionally fine-grained

Final Thoughts

Overall the stone fills some niches for me.  On the rare occasion where I need sashimi-slicing, clean, ultra edges, this is the one for single bevels or when I just want a short sharp burst of ultimate refinement on gyuto for a few dinner preps.  I also find myself reaching for it when I’m honing my one and only kamisori, the edge is comparable to that off a Maruka.  I have also rounded one of the long edges of the stone and I use this to finish hairdressing shears, the rounded edge allows me to finely debur the ura of Japanese scissors in a sort of modified, micro uraoshi.

I hope you’ve all enjoyed the post. Hit us up with any suggestions or questions or content requests.

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