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Initial Impressions on Aizu (for the edge)

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JDC

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Finally have some time to write about the Aizu I recently acquired, let's jump right in!

This small specimen has a "HS35" written on the side, so I'm guessing it's a Watanabe Aizu.

Front:

DSC_7868.jpg


Back:
DSC_7891.jpg


Quite an eye candy, isn't it?

A disclaimer before I go to the details: the following are just my impressions from initial testings, which bound to this specific stone, this specific knife, my specific usage, and my sharpening ability. The generalizability is unknown.

Back on track, this stone is pretty hard, smells like freshly cut grass mixed with damp limestone powder.
The speed is on the slower side with water only, and medium with a thin diamond slurry.

I tested the Aizu on my daily driver - a R2 that I'm thinning:
Milli Bevel.jpg


The knife has a 50mm height, so the edge here is a bit smaller than 1mm.
Usually I'll zero ground my knives then add a micro-bevel, but to make the edge bevel clearer under the scope, I enlarged the micro-bevel to a "milli-bevel". Given how thin the blade is, the "milli-bevel" imposes almost no difference in cutting.

Before hitting on the Aizu, I polished the edge progressively: SP 1000 -> SP 2000 -> King 6000 then strop on a hard Ozuku -> Four very light edge trailing (~45 degrees) strokes on the Ozuku to make a "nano-bevel."
The idea is to make the edge bevel finer for easy revelation of Aizu's scratch pattern later.
The last step is unnecessary, but for my daily edge I often put a "nano-bevel" on Ozuku or hard Nakayama following the SP 1000, I wanted to see what Aizu's gonna do with that.

1000.JPG2000.JPG6000 2 Ozuku Stropping.JPG6000 3 Ozuku Nano.JPG

Following this progression, I first stropped the edge on the Aizu with water only (~15 round trips):
A_Aizu Stropping.JPG

Under the scope, the "nano-bevel" is still there, the Aizu only added some light scratches to the bevel. On the cutting board, this edge was nothing special, just very polished.

After this, I raised a light slurry using a worn Atoma 400, and gave the edge a full sharpening on the Aizu, which removed the "nano-bevel" completely:

B_Full Aizu.JPG
It's a bit difficult to see because of the reflection, but if you compare the bottom portion with the previous image, a new apex is formed.
This edge was quite coarse, way coarser to my taste. Maybe I haven't mastered deburring on the Aizu.

I then gave the edge some stropping on the Ozuku:
C_Aizu_Ozuku Stropping.JPG
Voila! I now have a pretty good edge. Polished yet toothy, cuts everything really well.

To compare with my daily edge, I sharpened the knife on SP 1000 and put on a Ozuku "nano-bevel", then cut a bunch of vegetables.

I'd say my daily edge feels quite similar. A touch toothier than the Aizu and a bit less polished, but I'm really splitting the hair here. This edge provides more feedback than Aizu + Ozuku when cutting.

One interesting observation is: pull cutting was a bit easier than push cutting for my daily edge, while the edge from Aizu+Ozuku excelled in either styles.
 

Rangen

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Do you find that you need to avoid the black spots, or are they OK?
 

JDC

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Do you find that you need to avoid the black spots, or are they OK?
What do you mean by black spot? The renge (flower shaped) on the back side or the goma (sparse dots) on the front? The gomas are no problem, and I haven't tried the back side.
 

Rangen

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Ah, I was inattentive. The spots were indeed only on the back side. I saw them, thought they looked like what's on a stone I bought from Watanabe. His description suggested avoiding them entirely, so I saw what looked like the same sort of spots on your stone, and posted my question. But if they're just on the back side, it's not much of a question.
 
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Badgertooth

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Interesting write up, thank you for sharing. I don’t think I’ve ever gone into it as empirically or methodically as you have here but I wonder if in doing so you haven’t circumvented some of the Aizu magic. This might sound a little fluffy and subjective but for me it’s a kind of “ragged refinement”. I like to use it after a well formed 1k edge or even a 500 edge and part of its magic seems to be how it loosens and breaks lower grits burrs. If yours is true to type you should be left with a wonderfully aggressive, toothy edge. To my mind the Ozuku afterwards would be like hitting the mute button even if it makes it more keen in terms of observable scratches and bevels.
 

JDC

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Thanks for the comments!
Following your suggestion, I tried Aizu right after SP 1000. The edge right off SP 1000 cut paper towel cleanly.
However, the edge off the Aizu didn't cut paper towel well. It seems a new burr was formed from the Aizu and was not removed completely. If so the Aizu doesn't deburr as quickly as my low~mid grit synthetics.
I further deburred on the Aizu with more edge leading strokes, and the edge became much cleaner. Cutting vegetables felt great, but still in the near neighborhood of my daily edge. Maybe the difference will be more pronounced if the edge bevel is larger, but I don't have such a blade 😅
 

Alder26

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Interesting findings. In my experience (3-4 Aizu) Aizu tend to work best when you have polished your primary bevel a bit before working the edge. Something about softer cladding material really pulls a nice slurry from the stone and helps it cut. The grit of the finish can vary a decent amount depending on the stone, but the way it cuts is always nasty. Someone on here described a good Aizu edge as “violent” and I would tend to agree.
 
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JDC

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Interesting findings. In my experience (3-4 Aizu) Aizu tend to work best when you have polished your primary bevel a bit before working the edge. Something about softer cladding material really pulls a nice slurry from the stone and helps it cut. The grit of the finish can vary a decent amount depending on the stone, but the way it cuts is always nasty. Someone on here described a good Aizu edge as “violent” and I would tend to agree.
Kicking up some slurry is definitely important to get thing going on the Aizu. Maybe a slurry from the soft cladding is better than one forced from a diamond plate.
 
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