Question about kasumi with mirror core

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mrmoves92

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TLDR: When polishing, the core steel on my non-dominant side comes out hazier than on my dominant side. What causes the mirror core? How do you consistently achieve a kasumi with mirror core steel?

Hello!

I recently spent some time working on polishing. I got some good looking (at least to me) polishes (especially on my dominant side), but I don’t really know what I am doing. I am left handed, so I have more experience polishing the left side. I was able to get good contrast with hazy cladding on both sides, but I was only able to get a mirror like core steel on the left side. The right side has some sections that are pretty reflective, but it is much hazier than the left side. The knife is stainless clad white #2. I used the following progression: Nanohone 200 -> SG500 -> NP1k -> SG2k -> JNS red Aoto -> Morihei 9k. Here is what it looks like:

Left side:
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Right side:
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I tried doing the same thing to both sides, but I got slightly different results. It makes sense that the left side is better because I am more comfortable/experienced on that side, but I would like to have the same results on both sides.

Do you have any ideas why the right side would be hazier? Where could I have gone wrong? At what point in the polishing progression is most important for getting a mirror core? Does it look like I didn’t erase scratches from a coarser grit, or does it seem more related to technique? How do you do it consistently? Maybe I will try some diamond paste on balsa like @cotedupy is suggesting in his thread.

I have some ideas about where I could have gone wrong, but I would love to hear what you think. Here are my ideas:
1. I don’t think that I made the right bevel as consistent as the left bevel, so in order to get an even finish on the right side, I let more mud build up on the stone, and I used lighter pressure. I didn’t have to be as careful on the left side. Would letting mud build up and using lighter pressure make the core steel hazier even with a 9k stone?
2. Because I am not as comfortable/experienced with sharpening or polishing right handed, my finger placement on the knife with my left hand is not as good, so by the time I got to the SG2k, I had worn through the skin on two of the fingers on my left hand. On the left side with the SG2k, I started getting a mirror-ish/more reflective core steel when I applied really heavy pressure on or near the core steel, but because of my fingers, I couldn’t apply the same pressure and get the same results on the right side. Would this prevent the core from becoming mirror-like on the right side, or should I have been able to resolve this on the JNS red Aoto or the Morihei 9k?

Thank you for your help! I really appreciate it.
 

cotedupy

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A couple of thoughts (with the usual disclaimer that I don't really know what I'm talking about, and it's probably better to listen to others):

High mirror polishes as you say, come from fast work, with more pressure, on cleaner stones. This applies really to most stones regardless of grit. If you start pushing into really fine naturals (or indeed pastes!) then it doesn't matter so much, but on a 9k synth I imagine you'll still get a noticeable difference. The payoff though is that when you work like this you can start burnishing / polishing the cladding in ways you don't want. It's just a tightrope you have to walk.

A lot of Japanese knives have very slight rh bias to the grinds, i.e. more convexity to the main bevel on the rh side. That could be playing into it.

JNS Synthetic Aoto to Morihei 9k is probably quite a large jump for polishing, especially as the Red Aoto is a 2k/4k blend. Maybe worth looking at something in between them (?)

I think diamond balsa is probably actually exactly what you want though tbh. It was for exactly this kind of thing that I tried it out, and seems to work very well. Plus it's dead easy, and allows for convex polishing.

---

But mostly I couldn't have put it any better than you did yourself... it's just about just rubbing the knife on the stone til you're happy with it, and knowing when to stop before you feck it up!
 
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EricEricEric

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I approach one side right-handed I approached the other side left-handed, for me this helps ensure that everything is as even as possible as the technique is exactly the same for each side

The number one idea is to ensure that the geometry is correct, next goal is to get the core steel to a mirror finish, final goal is to use a finishing stone which will preserve the mirror finish of core steel while creating a hazy finish on the soft iron

On this knife that I’m showing it’s the finest Kasumi finish I’ve ever created with 100% stone

Shapton pro 150-5k, never ever use hard stones towards the finishing process, only soft stones so I stop at 5K

After that I switch over to a shiro nagura, The stone is prepared with 24 hour soak in water, and the finest small nagura you can get your hands on to create a strong slurry

I use short strokes with very light pressure allowing the stone and slurry to do all of the work

The shiro nagura makes for a very clean and bright finish with lots of detail

I will say that soft stones make for incredibly easier work in my experience. The majority of shapton stones that I use are all of the soft ones relatively speaking, the shiro nagura I use is a relatively hard stone so I make sure that I’m extra light on that stone in order to help ensure even results

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EricEricEric

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This is the same exact knife however I stopped at shapton 2K and finished on a soft strong Ohira shiro suita, the soft suita gave me more liberty and technique is not as crucial as it’s a soft stone

With this stone I’ll try to be mindful of keeping the pressure of my fingertip on the very edge of the blade so that the majority of the pressure is on the steel as opposed to the iron.

In my experience kasumi finish usually comes out best on iron with soft/light pressure, while steel seems to respond better to more pressure

However, I want to point out it will really depend on the effect the stone is having on the steel vs the iron. You will have to experiment with those concepts and decide how the stone is working in the situation and use that to your advantage

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