# Increased Resistance When Cutting due to Kasumi Finish



## Martyfish (Oct 20, 2021)

I tried my hand at producing a kasumi finish on a soft stainless clad ginsan gyuto recently and I am really happy with how it turned out visually, however ever since I refinished it, the knife requires more force to get through tall / dense products than it did before the refinishing. It really feels like the blade grips once the knife is 10-15mm or so deep in the cut. Onions are especially unpleasant to cut now and it becomes noticeably more difficult towards the tallest section of the onion. Normally I would think of wedging, but the knife is ultra-thin behind the edge, freshly sharpened, it was performing well prior to applying the kasumi and the grind did not change in any major way during the refinishing process. Accordingly, I believe the kasumi finish is somehow adding a lot of surface friction when cutting and that is responsible for the increased resistance. Has anyone experienced anything similar and if so, how did you solve the issue? It should be noted that the grind is relatively flat, so that probably increases the influence that the blade finish compared to more convex grinds.

The refinishing process comprised the following:

I refinished the entire blade up to P3000 grit with sandpaper (almost a mirror finish).
I worked a slurry consisting of F1200 grit silicon carbide powder (approximately equivalent to the grit size found in 4000 grit whetstones) and Windex into the blade using a 2400 grit micro mesh pad (approximately equivalent to the grit size found in 1200 grit whetstones).
I used 0000 steel wool to work in the same slurry mix instead of the micro mesh pad.
I made photos of the refinishing process, which you can find in the link below and there is a choil shot in there as well, which represents the current condition of the blade:



Prior to the refinishing the blade looked subpar, but performed well, now it looks good but performs subpar. I’d like to find a combination of the two, but have very limited experience with kasumi finishes, so any help or advice would be much appreciated.


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## M1k3 (Oct 20, 2021)

Did you make the bevels flat? Or still some convexity?


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## tostadas (Oct 20, 2021)

Is it friction, or sticking? I have encountered both when refinishing blades. If have shoulders near the shinogi line at something like a shapton 1k finish, it will have a lot of drag, or what I would consider to be friction. On the other end of the spectrum, if I polish it up to like 5k grit, then the shiny sides end up sticking quite a bit (kinda like suction).

If you want to experiment some, I'd suggest simply sandpaper to start since it's consistent, and then you can introduce stones or mud as a variable once you set a baseline. I found that 800P sandpaper gives a good balance in performance where things dont really drag nor stick significantly. I would polish up to maybe 1000-1500P sandpaper, then drop back down to 800.

One more thing about grinds, I've experimented with both convex and flat grinds in this regard. I think the issue you are describing is not specific to one or the other.


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## Martyfish (Oct 20, 2021)

M1k3 said:


> Did you make the bevels flat? Or still some convexity?


The bevels are relatively flat, but there is some slight convexity. There are two choil shots in linked Imgur album that show what the grind looks like currently.


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## Pie (Oct 20, 2021)

There will be some friction issues down low but it looks like you’ve gone pretty high up, mirrored in the picture almost… turning it into a stiction issue it seems. Kasumi where the cladding is mirror polished tends to suction to wet ingredients, creating resistance especially when the wide bevel is fully in contact with the substrate.

Maybe consider dropping down to a finisher that gives some texture to the cladding? Not so much scratches but “frosty” as it were, and barely mirror polished at the steepest viewing angle. In my limited work with stones, it’s just beyond 3k, maybe even a good 1k, as prep, and muddled up gently on a soft prefinisher jnat. My apologies for not understanding how mesh pad and grit powder behave, but if you were to finish coarser, I believe stiction would decrease accordingly.

A bunch of my finishing stones leave the cladding mirrored up, and I find it irritatingly sticky on mushrooms of all things. Alternatively you could mad convex the blade face, reducing the contact patch between food and knife. But this is a much tougher, time consuming fix. Probably would be much better in terms of increasing performance tho.


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## Martyfish (Oct 20, 2021)

tostadas said:


> Is it friction, or sticking? I have encountered both when refinishing blades. If have shoulders near the shinogi line at something like a shapton 1k finish, it will have a lot of drag, or what I would consider to be friction. On the other end of the spectrum, if I polish it up to like 5k grit, then the shiny sides end up sticking quite a bit (kinda like suction).
> 
> If you want to experiment some, I'd suggest simply sandpaper to start since it's consistent, and then you can introduce stones or mud as a variable once you set a baseline. I found that 800P sandpaper gives a good balance in performance where things dont really drag nor stick significantly. I would polish up to maybe 1000-1500P sandpaper, then drop back down to 800.
> 
> One more thing about grinds, I've experimented with both convex and flat grinds in this regard. I think the issue you are describing is not specific to one or the other.


Thanks for your reply. I'd say it's friction, but I'm not sure. The increase in resistance has been most noticeable so far when making the initial vertical slices in an onion before dicing. During the slicing motion (when the blade is embedded 10-15mm into the onion) it just feels like the onion grips to the side of the blade, but the diced onion wasn't sucked onto the blade. An increase in friction is also noticeable when drying the blade, because the teatowel doesn't glide over the blade as smoothly as with my other knives.

I'll try reintroducing some surface roughness as you have suggested and see how it feels.


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## tostadas (Oct 20, 2021)

Martyfish said:


> Thanks for your reply. I'd say it's friction, but I'm not sure. The increase in resistance has been most noticeable so far when making the initial vertical slices in an onion before dicing. During the slicing motion (when the blade is embedded 10-15mm into the onion) it just feels like the onion grips to the side of the blade, but the diced onion wasn't sucked onto the blade. An increase in friction is also noticeable when drying the blade, because the teatowel doesn't glide over the blade as smoothly as with my other knives.
> 
> I'll try reintroducing some surface roughness as you have suggested and see how it feels.


Since you didnt do any alteration to the geometry (ie thinning), you can rule that out as a major contributor to the change. So that's good.


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## HumbleHomeCook (Oct 20, 2021)

I have an Akifusa that isn't mirrored but came quite smooth and pretty shiny. It hangs up in wet veggies like a horizontal onion cut.


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## Martyfish (Oct 21, 2021)

Pie said:


> There will be some friction issues down low but it looks like you’ve gone pretty high up, mirrored in the picture almost… turning it into a stiction issue it seems. Kasumi where the cladding is mirror polished tends to suction to wet ingredients, creating resistance especially when the wide bevel is fully in contact with the substrate.
> 
> Maybe consider dropping down to a finisher that gives some texture to the cladding? Not so much scratches but “frosty” as it were, and barely mirror polished at the steepest viewing angle. In my limited work with stones, it’s just beyond 3k, maybe even a good 1k, as prep, and muddled up gently on a soft prefinisher jnat. My apologies for not understanding how mesh pad and grit powder behave, but if you were to finish coarser, I believe stiction would decrease accordingly.
> 
> A bunch of my finishing stones leave the cladding mirrored up, and I find it irritatingly sticky on mushrooms of all things. Alternatively you could mad convex the blade face, reducing the contact patch between food and knife. But this is a much tougher, time consuming fix. Probably would be much better in terms of increasing performance tho.


Yeah I polished it up to P3000 with sandpaper and then used very fine silicon carbide powder, so it is certainly a smooth finish coupled with pretty flat bevels. It sounds like it could be suction like you describe.

I plan to reintroduce some surface roughness with P800 sandpaper and then reapply the kasumi finish using a coarser silicon carbide powder.

If I reintroduced any meaningful amount of convexity behind the edge then I'd loose a lot of height, which I'm not eager to do, and the knife was cutting well prior to the kasumi finish, so I think that altering the surface finish should hopefully solve the problem.


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## migwal (Oct 21, 2021)

When I thinned my Sukenari 240 ginsan gyuto I brought it up to chosera 5k then my aiwatani?(can’t remember what it’s called) natural stone from JNS. It was a foggy mirror finish. And despite following the beautiful convex grind it was definitely not moving as nicely through product. I would definitely describe it as suction, as opposed to friction. 
I then brought back the original finish using single stokes on 320 sandpaper over my leather strop sandpaper clamp contraption, so it looked like the original belt finish. Problem solved, better than new. Don’t know how this would look on a wide bevel, you could go horizontally following the length of the blade but obviously you won’t want this if you’re chasing that kasumi. But I definitely think your issues would be due to the smooth kasumi, considering the grind wasn’t flattened. Would love to hear how the kasumi looks and performs over the p800!


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## Steampunk (Oct 21, 2021)

There's a balance between suction/stiction, and corrosion resistance on blades.

The higher you polish, the more you can improve the blade's resistance to corrosion up to a point. High-polishes also slow patina formation, which can let you get somewhat more attractive patinas from food acids (Hot red meat, onions, peppers, etc.), rather than the ugly/scary brown & orange patinas from less acidic foods, or the red-rust that you get from trapped moisture on some more reactive claddings.

Even stainless, left at low low refinement, can get 'patina' (Or even rust.) in normal use. The polish is part of what makes 'stain-less' steel, 'stainless'. It's also part of what makes garlic, and other things stick to these blades in a crazy annoying way. Steels like AEB-L and Ginsan/19C27, especially (Which have just barely enough chromium to make them stainless.), patina/rust quite quickly when given coarse finishes. Nitrogen steels (14C28N, LC200N, etc.) see much less staining in normal use with a coarse finish.

However, the higher you polish (For corrosion resistance.), the more stiction/suction can form between the blade and ingredient. This is particularly bad on stainless (You mention Ginsanko.). Much less so on pure carbon with carbon cladding, which - due to the continual chemical reaction between the ingredient and the steel - is sort of 'non-stick'. You can polish carbon higher than stainless, without that nasty stickiness, and probably should to reduce its rustiness. However, even semi-stainless and non-nitrogen stainless steels can patina or rust quite quickly without the high-polish they are meant to have.

The coarser your abrasive, the higher Ra frequency the surface profile is, which creates less area in constant contact with the food, and less resistance up to a point. You can take this too far (Many sandblasted finishes are a 'bridge too far', as they go beyond reducing fluid resistance, and start introducing frictional resistance, by having peaks higher than the fluid in the cut can fill-in.)... Essentially, with stainless blades, you're trying to get some sort of balance between corrosion resistance, and hydroplaning the surface of the blade against the food that's pressing against it.

It's a trade-off. People in the marine trade don't polish to a high gloss for fun. It's practical.

If you're okay with patina on your blade slowly forming, you can probably leave it at King 800/JNS 800, or less with your Ginsan knife. Then take the micro-bevel a little higher in terms of refinement. Basically, the inverse of what you do on Shirogami when you want it to perform well on tomatoes (You polish the sides high, and you micro-bevel it coarse.).

@Martyfish ... You did a great polish job on the knife. That's a proper 'knife maker' finish. This is how it's done in the custom industry, when you want to impress people at shows. Big kudos for creating it; be proud... This isn't how it's done when you just want to get work done with the blade... Convex-thin the blade a little more heavily, possibly convex-zero (Think Virtuovice on YouTube, with a bit of a rocking motion. Ginsan seems to handle this really well, or with a very faint micro-bevel on a hard/slow finishing stone, like Arkansas, BBW, or an F.Dick Micro Rod... Rather than rocking on a stone, you can also use SiC sandpaper on a flexible backing, like a wet t-shirt rag.), and leave it a bit coarser in regards to the SiC paper/grit. It won't be as pretty as what you created, but will perform better in use.

Hope this helps.


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## migwal (Oct 22, 2021)

Wow, amazing info and insight. Thanks a bunch Steampunk!


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## Martyfish (Oct 22, 2021)

Steampunk said:


> There's a balance between suction/stiction, and corrosion resistance on blades.
> 
> The higher you polish, the more you can improve the blade's resistance to corrosion up to a point. High-polishes also slow patina formation, which can let you get somewhat more attractive patinas from food acids (Hot red meat, onions, peppers, etc.), rather than the ugly/scary brown & orange patinas from less acidic foods, or the red-rust that you get from trapped moisture on some more reactive claddings.
> 
> ...


Wow, thanks for your detailed response! Corrosion resistance is not really a big concern for me, but I would like to find a balance between reducing the contact surface area between the blade and the produce by introducing some surface roughness and introducing too much frictional resistance, by having peaks higher than the fluid in the cut can fill-in. I will expermient around a bit until I am happy with the aestetics and performance but my current plan is to reinroduce some surface roughness using P800 sandpaper and then reapply the kasumi finish using some F360 silicon carbide poweder. I hope this looks good and hits the middle ground between reducing the contact surface area and intruducing frictional resistance, but time will tell.

Oddly enough, the blade is a pleasure to use in its current condition, except when cutting onions and leek. The blade falls through tomatoes, potatoes and cucumber and there were surprisingly no issues with food release either. It just cant deal with the onion family. It also feels a bit weird when drying it with a wet cotton tea towel and does not slide into its felt blade guard very smoothly.

I want to avoid altering the grind if at all possible. The knife was performing well before I polished the blade and applied the kasumi finish and the grind was not altered in any meaningful way during these processes, so I am confident I can get it cutting well by altering the surface finish again. In the worst case scenario, I'll just have to finish it with a nice satin finish and leave the kasumi for other blades.

Thanks again for your response, it was very helpful.


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## Martyfish (Oct 22, 2021)

migwal said:


> When I thinned my Sukenari 240 ginsan gyuto I brought it up to chosera 5k then my aiwatani?(can’t remember what it’s called) natural stone from JNS. It was a foggy mirror finish. And despite following the beautiful convex grind it was definitely not moving as nicely through product. I would definitely describe it as suction, as opposed to friction.
> I then brought back the original finish using single stokes on 320 sandpaper over my leather strop sandpaper clamp contraption, so it looked like the original belt finish. Problem solved, better than new. Don’t know how this would look on a wide bevel, you could go horizontally following the length of the blade but obviously you won’t want this if you’re chasing that kasumi. But I definitely think your issues would be due to the smooth kasumi, considering the grind wasn’t flattened. Would love to hear how the kasumi looks and performs over the p800!


Thanks for your response and good to know that you noticed a difference after introducing some surface roughness. I'll be sure to update this post with the results once I have altered the finish, but it could be a few weeks until I get all the materials and the time to use them.


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## Martyfish (Nov 9, 2021)

migwal said:


> When I thinned my Sukenari 240 ginsan gyuto I brought it up to chosera 5k then my aiwatani?(can’t remember what it’s called) natural stone from JNS. It was a foggy mirror finish. And despite following the beautiful convex grind it was definitely not moving as nicely through product. I would definitely describe it as suction, as opposed to friction.
> I then brought back the original finish using single stokes on 320 sandpaper over my leather strop sandpaper clamp contraption, so it looked like the original belt finish. Problem solved, better than new. Don’t know how this would look on a wide bevel, you could go horizontally following the length of the blade but obviously you won’t want this if you’re chasing that kasumi. But I definitely think your issues would be due to the smooth kasumi, considering the grind wasn’t flattened. Would love to hear how the kasumi looks and performs over the p800!


@migwal and anyone who stumbles upon this post in the future, see the link below for a comparison between various finishes in addition to pictures of what the blade looks like currently (there are detailed descriptions of the process in the captions). Introducing some surface roughness absolutely helped and now the blade performs well and looks good.


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## migwal (Nov 9, 2021)

Well done mate, looking good! I can’t believe how bad it was (in performance, not looks) that’s crazy. Beautiful knife.


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## Martyfish (Nov 9, 2021)

migwal said:


> Well done mate, looking good! I can’t believe how bad it was (in performance, not looks) that’s crazy. Beautiful knife.


Thanks man . Yeah it's mental how bad it was, literally unusable. I am honestly still surprised that the surface finish had such an influence. Oh well, now it looks good and performs well and I learned something new in the process.


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## HumbleHomeCook (Nov 9, 2021)

@Martyfish excellent follow-up. Thank you.


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## Martyfish (Nov 9, 2021)

HumbleHomeCook said:


> @Martyfish excellent follow-up. Thank you.


No worries. I'm glad I could contribute something useful to the forum.


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## tcmx3 (Nov 9, 2021)

Martyfish said:


> @migwal and anyone who stumbles upon this post in the future, see the link below for a comparison between various finishes in addition to pictures of what the blade looks like currently (there are detailed descriptions of the process in the captions). Introducing some surface roughness absolutely helped and now the blade performs well and looks good.




that first video is just... wow.

thanks for posting that, Ive never seen a proper knife struggle that much to cut an onion and would struggle to believe it if not for the evidence right in front of my eyes.

does anyone have any comment about how different polishing media might effect this? for example, if you were somehow able to hit the whole face with something like a Shapton pro (or the more obvious natural fingerstones) at the same grit would you observe the same effect? never noticed anything even close to this off a natural.


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## tostadas (Nov 9, 2021)

Martyfish said:


> Thanks man . Yeah it's mental how bad it was, literally unusable. I am honestly still surprised that the surface finish had such an influence. Oh well, now it looks good and performs well and I learned something new in the process.



Was the difference between the sticky finish and the non sticky finish noticeable when not cutting through hard stuff? Like could you tell the difference when drying the knife with a towel?


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## Martyfish (Nov 9, 2021)

tostadas said:


> Was the difference between the sticky finish and the non sticky finish noticeable when not cutting through hard stuff? Like could you tell the difference when drying the knife with a towel?


The sticky finish in video 1 cut some ingredients fine (cucumber, tomato and potato), however other ingredients were really unpleasant to cut (onion, leek and carrot). I'd still classify potato as hard, but it didn't cause any issues. I can't remember if I cut anything else before I decided to alter the finish again, but hopefully that helps.

There sticky finish did grip slightly more to a wet tea towel, but just enough to be noticeable.


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## tostadas (Nov 9, 2021)

Martyfish said:


> The sticky finish in video 1 cut some ingredients fine (cucumber, tomato and potato), however other ingredients were really unpleasant to cut (onion, leek and carrot). I'd still classify potato as hard, but it didn't cause any issues. I can't remember if I cut anything else before I decided to alter the finish again, but hopefully that helps.
> 
> There sticky finish did grip slightly more to a wet tea towel, but just enough to be noticeable.


Good to know. Onion and carrot are my benchmarks because I go through a lot of those often.


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## McMan (Nov 9, 2021)

I need to go back and watch the links more carefully...
But I'd be surprised if that level of struggling through the onion is just related to finish.
That seems to me to speak more to blade geometry (BTE) and/or sharpness.


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## Martyfish (Nov 9, 2021)

McMan said:


> I need to go back and watch the links more carefully...
> But I'd be surprised if that level of struggling through the onion is just related to finish.
> That seems to me to speak more to blade geometry (BTE) and/or sharpness.


I can't really blame you for being sceptical, I did the work and I can barely believe it myself. That said, the only change between video 1 and 2 was introducing a scratch pattern with P600 grit sandpaper, which removed essentialy no material, certainly not enough to make any meaningful difference to the BTE thickness. The only change between video 2 and 3 was rubbing the F360 silicon carbide / Windex slurry into the blade with 0000 steel wool, which again removed essentialy no material and had no meaningful effect on the BTE thickness.

As far as sharpness goes, the edge was freshly sharpened in video 1 and freshly stropped on a Naniwa Pro 3k stone before video 2 and 3, because the refinishing dulled the edge ever so slightly.

The only meaningful change was the surface finish. Weird, but I'm 99.99% confident in the statements I've made, otherwise I wouldn't have posted them here.


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## tally-ho (Nov 9, 2021)

Martyfish said:


> @migwal and anyone who stumbles upon this post in the future, see the link below for a comparison between various finishes in addition to pictures of what the blade looks like currently (there are detailed descriptions of the process in the captions). Introducing some surface roughness absolutely helped and now the blade performs well and looks good.



The problem here is to not make horizontal cuts before vertical cuts. Without vertical cuts, the blade is "compressed" by both sides of the onion and there is not air between the blade and the quite dense surfaces that are wet = heavy suction from both sides.
If you ever sharpened a straight razor with a wedge grind (flat grind) the thinner the grit, the more suction you will have. The solution is to add more water and put no pressure on the blade to let it glide on the wetstone.


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## tcmx3 (Nov 9, 2021)

tally-ho said:


> The problem here is to not make horizontal cuts before vertical cuts. Without vertical cuts, the blade is "compressed" by both sides of the onion and there is not air between the blade and the quite dense surfaces that are wet = heavy suction.
> If you ever sharpened a straight razor with a wedge grind (flat grind) the thinner the grit, the more suction you will have. The solution is to add more water and put no pressure on the blade to let it glide on the wetstone.



Im not sure that is a satisfactory answer.

I always do horizontal cuts first; you make fewer of them and it makes things stay together more that way. I have NEVER experienced what the OP did & Id rather change my finish than my technique if Im happy with my technique (which for dicing onions I am). now if this were something that was true of a wide variety of finishes Id change my technique but if I use uchigumori powder (which I do) on full convex knives and dont see this effect, I think it's worth just finishing differently

clearly YMMV


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## tostadas (Nov 9, 2021)

tcmx3 said:


> I have NEVER experienced what the OP did & Id rather change my finish than my technique if Im happy with my technique (which for dicing onions I am). now if this were something that was true of a wide variety of finishes Id change my technique but if I use uchigumori powder (which I do) on full convex knives and dont see this effect, I think it's worth just finishing differently
> 
> clearly YMMV


I also havent noticed this level of sticking when using natural stones or powders. However, I did experience it when I went beyond like P2000 sandpaper, and similar with a finish off a Shapton pro 5k.


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## ew_ut (Aug 18, 2022)

Just rereading this… cool and informative thread, @Martyfish!


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## ian (Aug 18, 2022)

Fwiw, in those vids the cuts are more straight down in the first vid and have more pull in the other two, which might accentuate the perceived difference. But yea, the knife sure looks like it’s struggling in the first vid. Surprising.


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## Martyfish (Aug 18, 2022)

ian said:


> Fwiw, in those vids the cuts are more straight down in the first vid and have more pull in the other two, which might accentuate the perceived difference. But yea, the knife sure looks like it’s struggling in the first vid. Surprising.


From what I can see, the initial 3 cuts in video 1 have more or less the same pull as in videos 2 and 3, but from cut 4 the knife starts sticking / gripping like crazy and that made the pull technique almost impossible. Even a straight down cut with a lot of force was very difficult at this point, as you can see from the hand shake in my left hand during the final 3 cuts. So you're kind of right, but the change in technique was the result of the sticking / gripping and not vice versa.


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