Polishing knife

[Artur]

Hello knife community !
I have a gyuto 21 cm aogami 2 (kurouchi).
I really like the mirror polish.
I have never polished a knife but I would like to try it )
Give me some advice I need to buy sandpaper from 120 to 3000 ?and that's it ?
There are very few videos that show exactly how to polish a knife properly.
Thank you all for your help.

 

[KasumiJLA]

Hi Artur

Polishing is a super nice rabbit hole to jump in! You will learn a lot by doing your first knife and you'll still learn when you get to your fiftieth polished knife. Prepare to suffer at first and be disappointed. Really. But with practice and a lot of determination, you will develop techniques and better understand how steel can react on your stones. After that, you will become addicted!

You can obviously use sandpaper, but for this kind of knife it is much easier to do it on stone. It's gonna be easier, more crisp and visually more appealing. By doing it on stone you will thin this knife a bit and it's gonna be a good thing too for the performance point of view.

I don't know your setup but here's my go to for polishing a knife:

Shapton 220 - This is the main stone, the foundation of your perfect bevel. Without a good job on a coarse stone, don't even think about the subtle reflection of your final polisher. You need to master your coarse stone and make everything flat and even by removing every factory scratch pattern first.

Shapton 320 - It's not a big jump right? Well, it's just enough to reveal if the job was well done on your previous stone. Keep in mind that polishing is 90% of tedious work on coarse stone and 10% of fun factor on the final one. It is much more efficient to make a tight progression on a coarser grit than to go too fast and discover scratches later.

Naniwa pro 400 - I just love this stone. But don't be fool by the 400 grit size, it's in fact more finer than that. I use it like a ~600 stone. The Naniwa 400 will show you every little defect and this grain size is still enough to correct some area that you miss previously.

Naniwa pro 1k or softer imanishi - It's really up to you if you want to work on a harder stone or softer at this point. With softer stone et gonna be more forgiving and you will access little spots more easily. With a harder stone you will reveal every mistakes but you will be rewarded with a crisp shinogi. At this point on the 1k stone, if you find some imperfections, you have to go back to 400 to erase them before continuing on finer stone.

Naniwa super 3k - This is the chalky, super fast burnishing stone that will make you smile when you will reach a mirror hagane! I just love this stone, but only for polishing. I hate to sharpen on it because it's too soft. You can achieve a kasumi on this stone but it requires a lot of trial and error. Try with mud, without, pressure, less pressure etc. At this point you should have something clean and you'll be happy with it!

To infinity and beyond - This is where your wallet starts to hurt, your passion becomes worrying and your friends no longer understand why you don't leave your house anymore. You start to have a strange obsession with stones, with deep search in Japanese on YouTube and constantly looking at this tread on KKF. But this is where you can really bring out the beauty of steel

Have fun!

 

[Nemo]

This is a pretty deep rabbit hole and probably a lot more work than you realise.

How you should approach this depends on the grind. I have never handled this knife but I suspect that it is most likely a slightly concave grind. If this is the case, you will need to flatten the bevels with a coarse stone if you want to use stones. This is quite a bit of work, as there are often low spots which don't show up until you start grinding. Otherwise you could use sandpaper, which will conform to the shape of the bevel, but it may be harder to preserve the crisp shinogi.

If polishing with sandpaper (and even with stones), it's not that difficult to accidentally give yourself a pretty serious laceration. I tend to dull the knife by very gently breadknifing on a fine stone before undertaking this. This technique of dulling makes it pretty easy to restore the edge later on.

A full mirror polish progression will need to go above p3000. I have had some success finishing a progression on p3000, then using a fine metal polish. I have Mothers' MAG Polish but other polishes such as Flitz, Simichrome or some of the Japanese brands probably work similarly.

In order to do a full mirror poish, you will need to be sure that you have removed all scratches from the previous grit before proceeding to the next grit. Otherwise you put your knife on a fine stone and all of a sudden you get to see the 180 grit scratches that you had missed before, so it's all the way back to the start. It's a lot more work than you probably realise.

A full mirror polish will also likely worsen food release.

One alternative is to use a semi mirror polish, finishing in the 1500-2000 grit range. This doesn't show up as many of the scratches that you missed in the lower grits and can still look pretty decent. It's also usually a bit of a sweet spot for food release, not to metion being a decent fall back position if you try a full mirror, only to have all of the scratches show up when you polish at 3k or above.

 

[Artur]

Hi Artur

Polishing is a super nice rabbit hole to jump in! You will learn a lot by doing your first knife and you'll still learn when you get to your fiftieth polished knife. Prepare to suffer at first and be disappointed. Really. But with practice and a lot of determination, you will develop techniques and better understand how steel can react on your stones. After that, you will become addicted!

You can obviously use sandpaper, but for this kind of knife it is much easier to do it on stone. It's gonna be easier, more crisp and visually more appealing. By doing it on stone you will thin this knife a bit and it's gonna be a good thing too for the performance point of view.

I don't know your setup but here's my go to for polishing a knife:

Shapton 220 - This is the main stone, the foundation of your perfect bevel. Without a good job on a coarse stone, don't even think about the subtle reflection of your final polisher. You need to master your coarse stone and make everything flat and even by removing every factory scratch pattern first.

Shapton 320 - It's not a big jump right? Well, it's just enough to reveal if the job was well done on your previous stone. Keep in mind that polishing is 90% of tedious work on coarse stone and 10% of fun factor on the final one. It is much more efficient to make a tight progression on a coarser grit than to go too fast and discover scratches later.

Naniwa pro 400 - I just love this stone. But don't be fool by the 400 grit size, it's in fact more finer than that. I use it like a ~600 stone. The Naniwa 400 will show you every little defect and this grain size is still enough to correct some area that you miss previously.

Naniwa pro 1k or softer imanishi - It's really up to you if you want to work on a harder stone or softer at this point. With softer stone et gonna be more forgiving and you will access little spots more easily. With a harder stone you will reveal every mistakes but you will be rewarded with a crisp shinogi. At this point on the 1k stone, if you find some imperfections, you have to go back to 400 to erase them before continuing on finer stone.

Naniwa super 3k - This is the chalky, super fast burnishing stone that will make you smile when you will reach a mirror hagane! I just love this stone, but only for polishing. I hate to sharpen on it because it's too soft. You can achieve a kasumi on this stone but it requires a lot of trial and error. Try with mud, without, pressure, less pressure etc. At this point you should have something clean and you'll be happy with it!

To infinity and beyond - This is where your wallet starts to hurt, your passion becomes worrying and your friends no longer understand why you don't leave your house anymore. You start to have a strange obsession with stones, with deep search in Japanese on YouTube and constantly looking at this tread on KKF. But this is where you can really bring out the beauty of steel

Have fun!

I just watched the movie TopGun Maverick
As Maverick was teaching the pilots at the Academy, I felt the same way reading your post )))
Great explanation thank you ))))
If possible please send me pictures of your knives

 

[KasumiJLA]

Yanagiba restoration to complete mirror, ura included

Yanagiba restoration to full kasumi.

My most recent polish on this gyuto.


Honyaki restoration

A nice petty all on natural stones

 

[Repjapsteel]

What are some signs that you're done with the stone and ready to move on to the next step?

 

[mockit]

@Repjapsteel Ideally you want to use a stone as little as possible to make the finish even. No dark or bright spots indicating lows/highs. There will always be some convexity but you want to avoid grinding along facets. Once the finish is nice and even you can try to go up to a higher grit. You want to make sure you are "erasing" coarse scratches with a finer stone. One way to check this is to alternate directions between stones. Once all the longitudinal scratches become 45 or 90 degrees... you know all the scratches are gone. It is not always a linear process because different stones reveal different flaws in the finish. You may get to 2-3k and realize there is a bad low spot somewhere.

 

[KasumiJLA]

You may get to 2-3k and realize there is a bad low spot somewhere.

It is at this precise moment that you try to convince yourself that the scratch does not bother you...

And you finally start again at 400 grit

 

[user 16756]

What are some signs that you're done with the stone and ready to move on to the next step?

you can change direction and erase all the scratches from the previous polishing direction easily and quickly. along the entire bevel.

this is an indication that your geometry is at least even, though it's no guarantee it's good.

 

[Repjapsteel]

This may be a dumb question but do I want to keep the same pressure for all the stones?
would more pressure create faster cutting with the lower grit stones?
I know how to sharpen knives decently enough (able to cut paper towels) but I never have done thinning or polishing.
Also thank you everyone for your answers so far!

 

[KasumiJLA]

@Repjapsteel for me it's super important. Finger placement and pressure will impact the results. Since we don't see what we're doing, we work in mirror image on the other side. Where I place my fingers is exactly where I decide to remove steel. I work in three instinct zones, here is my way of doing it.

Finger place in the middle of the kireha - it's the basic thinning placement to see where the stone touch on my bevel. Most of my work is made on this spot. It's a moderate pressure.

Finger place near the shinogi - This is where I try to refine that shinogi line and I put more emphasis from 1k stone. I use small strokes and small amount of pressure.

Finger place on the hagane - SUPER HARD pressure, that steel can hide previous scratches very well. And when you think you're done, just continue for 5 more minutes

Edit : I keep the same rules from 220 grit to 5k and/or natural stones.

I know we all polish with different techniques, but my vision is simple: hard steel = hard pressure and soft steel = less pressure.

 

[Jovidah]

Keep in mind that while mirror polishes may be pretty, they also make the blade a lot more sticky. Your food release will get noticably worse.

 

[mengwong]

And they last exactly one use and then, boom, splotchy patina