Dumb questions about improving food release to an existing blade

[NameAlreadyTaken]

Apologies in advance for the dumb questions. I know the answers for these have been discussed already but for the life of me, I can't seem to find the right threads with the advanced search box (but have enjoyed reading the many other threads that I thought would tell me the answers ).
Okay, the back story here is I did all my Christmas prep with a 57mm tall nakiri, which (as far as I can tell) is a wide bevel flat V grind, and it got me wondering what I could do to tinker with it to try and improve the food release. That started my researching, which coalesced into the following questions:

1) Surface: Is there a generally agreed grit count for a sandpaper finish that is better (or less bad) for food release? Best that I could find from my research was that anything other than a high grit or mirror finish would promote less contact between wet product and the blade (it currently has a hairline / sanded finish so I'd only be tinkering a little bit to change the existing grit finish).

2) Convexity: Is there any effective way to incorporate convexity into an existing flat grind wide bevel that could improve food release? Here I'm ruling out a full convex regrind as I don't have the skills or a water cooled belt grinder, but intuitively it doesn't seem like I would benefit at all from rounding / blending the shinogi line with sandpaper would be worth while, as it may just make more product slide more easily up the height of the blade? Likewise, it doesn't seem to me like a higher bevel angle for the edge would make a material difference? Keen to hear any thoughts or opinions?

3) S grind: Rereading Kipp's fine threads on asymmetry and the hook grind thread, as well as some other threads on s-grinds, it kind of seems like an option that I would have would be to try and sand an air gap on the right hand side (I'm a righty) just above the shinogi line to try and interrupt the product in it's progression up the height of the blade? Is that even worth considering as an option? Has anyone toyed around with after market mods of this nature and any suggestions?

Thanks in advance!

 

[miggus]

Hi! That is an interesting, justified and thoughtful question!

The following things might help get you answers:

Are you lefthanded?
Is your knife symmetrical?
Which model of knife are you using?
Can you post a choil shot?
Can you post a pic of the full knife? (Not needed, but 57mm tall Nakiri sounds awesome, I wanna see please )

 

[McMan]

I think sometimes what gets lost in discussions of food release is that technique has a significant impact. Speed (slower cutting = less release), push/pull, part of knife used, etc. Also, height matters a good deal--the more height the more surface area. Plus, type of product (dry/wet, hard/soft/spongy, etc. etc.) matters too.

1--Common wisdom says no mirror, but I think this is overstated. Some of the sandblasted finishes can be a bit too grippy. This might be a case where actually going to a higher grit would help. You could experiment--try a few different finishes and make note of which works best for you. 800 would be a good starting point.
2--Not likely. Food release is a product of the grind. You can't put metal where it's not. You could try blending the shoulders, which may help a tiny bit (or not at all).
3--Could be a fun experiment, if you've got a dremel and time. But I'm inclined to think the gains would be marginal. Food release is still a product of grind, fuller or no fuller. So, while a fuller might create an air gap, it won't alter the performance on the grind. Also, it's possible the knife might be too thin to add a fuller of significant enough depth.

All this to say, the correct answer to your questions is: Time for a new knife

 

[Dull_Apex]

For point 3, did you find this thread by @ian?

https://www.kitchenknifeforums.com/threads/hand-sandpapering-in-some-concavity.46427/

 

[NameAlreadyTaken]

For point 3, did you find this thread by @ian?

https://www.kitchenknifeforums.com/threads/hand-sandpapering-in-some-concavity.46427/

Thanks for that! I remember reading that now. Looks like I’ll do a similar project to Ian…. Hmm might take me a while though. Good to know there’s others that had somewhat positive outcomes!

 

[NameAlreadyTaken]

I think sometimes what gets lost in discussions of food release is that technique has a significant impact. Speed (slower cutting = less release), push/pull, part of knife used, etc. Also, height matters a good deal--the more height the more surface area. Plus, type of product (dry/wet, hard/soft/spongy, etc. etc.) matters too.

1--Common wisdom says no mirror, but I think this is overstated. Some of the sandblasted finishes can be a bit too grippy. This might be a case where actually going to a higher grit would help. You could experiment--try a few different finishes and make note of which works best for you. 800 would be a good starting point.
2--Not likely. Food release is a product of the grind. You can't put metal where it's not. You could try blending the shoulders, which may help a tiny bit (or not at all).
3--Could be a fun experiment, if you've got a dremel and time. But I'm inclined to think the gains would be marginal. Food release is still a product of grind, fuller or no fuller. So, while a fuller might create an air gap, it won't alter the performance on the grind. Also, it's possible the knife might be too thin to add a fuller of significant enough depth.

All this to say, the correct answer to your questions is: Time for a new knife

Good point about the technique. I really only thought of it after doing a few days of Christmas prep with a variety of different soft and hard veggies, mainly push cutting and chopping. The height certainly is a factor, which is great for comfort and usage, but presents a lot more surface area for product to stick to.
I reckon an 800 grit finish might be finer / higher than what it has at the moment, which if that’s the case, I’m guessing there’d be slightly less resistance from the slightly smoother surface? But I’m guessing there’s got to be a reason why so many knives are finished to that kind of level, right?

 

[stringer]

There are a lot of threads on this topic. I know you said you read some of them. Here is a curated list of some of my favorites. Maybe one of these will help and now I can link to this post when someone asks again in a few months.

Thread 'Food Release: Stiction and the Grind' Food Release: Stiction and the Grind

Thread 'Convexity, flatness, stiction and food release' Convexity, flatness, stiction and food release

Thread 'Cross-sectional thickness, convexity, asymmetry, and impact on cutting behavior' Cross-sectional thickness, convexity, asymmetry, and impact on cutting behavior

Thread 'Thinning, Grinds, and Food Release' Thinning, Grinds, and Food Release

TLDR; There are many opinions. My opinion is that most food release problems are technique issues. If a knife is truly horrible with stiction then don't use it for tasks where stuff sticks or change your technique. If you like to use and change your knives then you can play around with different surface finishes. You can also add some micro convexity behind the edge. This will make your edge stronger and improve food release but sacrifices some ultimate sharpness.

 

[Ochazuke]

There are a lot of threads on this topic. I know you said you read some of them. Here is a curated list of some of my favorites. Maybe one of these will help and now I can link to this post when someone asks again in a few months.

Thread 'Food Release: Stiction and the Grind' Food Release: Stiction and the Grind

Thread 'Convexity, flatness, stiction and food release' Convexity, flatness, stiction and food release

Thread 'Cross-sectional thickness, convexity, asymmetry, and impact on cutting behavior' Cross-sectional thickness, convexity, asymmetry, and impact on cutting behavior

Thread 'Thinning, Grinds, and Food Release' Thinning, Grinds, and Food Release

TLDR; There are many opinions. My opinion is that most food release problems are technique issues. If a knife is truly horrible with stiction then don't use it for tasks where stuff sticks or change your technique. If you like to use and change your knives then you can play around with different surface finishes. You can also add some micro convexity behind the edge. This will make your edge stronger and improve food release but sacrifices some ultimate sharpness.

+1

Just to add my own little thought on why technique makes a difference: people who cut hesitantly experience more stiction. I don't know if it's lack of technique or people wanting to baby their knife edge. Once you gain a certain amount of proficiency and speed, a lot of stiction issues seem to disappear. People who blast through prep rarely experience stiction issues.

I think it's a mixture of the speed of the knife, pushing ingredients out of he way as the cut happens, and how contact with the board knocks ingredients off the blade. Neither of these two things happen when the cutting motion is slow and hesitant.

I haven't seen you cut, so I don't know if this is your issue, but it is food for thought.

 

[NameAlreadyTaken]

There are a lot of threads on this topic. I know you said you read some of them. Here is a curated list of some of my favorites. Maybe one of these will help and now I can link to this post when someone asks again in a few months.

Thread 'Food Release: Stiction and the Grind' Food Release: Stiction and the Grind

Thread 'Convexity, flatness, stiction and food release' Convexity, flatness, stiction and food release

Thread 'Cross-sectional thickness, convexity, asymmetry, and impact on cutting behavior' Cross-sectional thickness, convexity, asymmetry, and impact on cutting behavior

Thread 'Thinning, Grinds, and Food Release' Thinning, Grinds, and Food Release

TLDR; There are many opinions. My opinion is that most food release problems are technique issues. If a knife is truly horrible with stiction then don't use it for tasks where stuff sticks or change your technique. If you like to use and change your knives then you can play around with different surface finishes. You can also add some micro convexity behind the edge. This will make your edge stronger and improve food release but sacrifices some ultimate sharpness.

Thanks Stringer!
Some great links (some that I didn’t get from the search).
I’ll need to add changes to my technique to the list as well.

Are there any push cut technique vids that you would suggest? I’m not specifically unconfident with my technique but maybe watching others on slow motion I could pick up some pointers?

 

[NameAlreadyTaken]

+1

Just to add my own little thought on why technique makes a difference: people who cut hesitantly experience more stiction. I don't know if it's lack of technique or people wanting to baby their knife edge. Once you gain a certain amount of proficiency and speed, a lot of stiction issues seem to disappear. People who blast through prep rarely experience stiction issues.

I think it's a mixture of the speed of the knife, pushing ingredients out of he way as the cut happens, and how contact with the board knocks ingredients off the blade. Neither of these two things happen when the cutting motion is slow and hesitant.

I haven't seen you cut, so I don't know if this is your issue, but it is food for thought.

That certainly makes a lot of sense, that the kinetic force of the board impact would provide a bit of a dislodging effect to shake things free from the blade more easily. I’m not specifically unconfident with my technique but I’m always interested in improving. Any vids that you’d suggest?

 

[Benuser]

You can also add some micro convexity behind the edge. This will make your edge stronger and improve food release but sacrifices some ultimate sharpness.

This is especially helpful if combined with off-centering the edge to the left — for right-handers, of course. That's what I did with a very light K-Sabatier 200 series in 14C28N.

 

[NameAlreadyTaken]

This is especially helpful if combined with off-centering the edge to the left — for right-handers, of course. That's what I did with a very light K-Sabatier 200 series in 14C28N.

Oh right. So perhaps moving from a 50:50 grind to a 60:40 grind over time might also introduce a little bit more subtle asymmetry?
I’m guessing that would be achieved by over sharpening on the right hand side (to remove more metal than the left hand side), progressively over time? Or is it really only thinning that’s going to move the position / ratio of the edge bevel?

 

[Benuser]

Oh right. So perhaps moving from a 50:50 grind to a 60:40 grind over time might also introduce a little bit more subtle asymmetry?
I’m guessing that would be achieved by over sharpening on the right hand side (to remove more metal than the left hand side), progressively over time? Or is it really only thinning that’s going to move the position / ratio of the edge bevel?

Both are needed. Thinning behind the edge alone won't change the edge's position. You may off-center it by raising a few times a fat burr on the left side that you only cautiously abrade. You want the right bevel to form a continuous arc with the right face, so you ease the shoulder. It all sounds dramatic, it is not. You may achieve it with the right bevel by starting at a very low angle and only little by little raising the spine until the new, off-centered edge has been reached. Make sure with a sharpie and a loupe you have a totally clean bevel. A burr may occur before the very edge got reached.

 

[mengwong]

That certainly makes a lot of sense, that the kinetic force of the board impact would provide a bit of a dislodging effect to shake things free from the blade more easily.

The S grind is special because, when the knife moves downward, its hollow caves away from the food, and a gap appears.

A pull cut creates the same gap! Due to distal taper, when the knife moves heelward, the potato halves are 4mm apart but the tip is less than 1mm! So 3mm of air on at least one side.

Continuing the pattern: a speedy return on a push cut chop also creates a gap – due to convexing, on the upward stroke! The taper from spine to edge kicks in when the inertia of the food exceeds stiction – like the tablecloth whipped away.

The slow knife suffers static friction; the fast knife enjoys kinetic (less) friction.

 

[NameAlreadyTaken]

The S grind is special because, when the knife moves downward, its hollow caves away from the food, and a gap appears.

A pull cut creates the same gap! Due to distal taper, when the knife moves heelward, the potato halves are 4mm apart but the tip is less than 1mm! So 3mm of air on at least one side.

Continuing the pattern: a speedy return on a push cut chop also creates a gap – due to convexing, on the upward stroke! The taper from spine to edge kicks in when the inertia of the food exceeds stiction – like the tablecloth whipped away.

The slow knife suffers static friction; the fast knife enjoys kinetic (less) friction.

Thanks for the explanation. That makes a lot of sense.

 

[Benuser]

You may see if the so‐called Kesselscher Walkschliff may help you. It's done by heavily rounding the spine, in fact, by reducing its width. I apply it only on the dominant — right — side. I want the left side to remain more or less sharp for moving produce on the board. Of course, it has more consequences. It reduces somewhat the blade's weight and so the balance. Rücken = spine; Balligkeit = convexity; Klingen-Querschnitt = the blade's cross-section.

 

[bsfsu]

I agree with @stringer on this one. Stickation is minimized by better knife control. Micro adjustments, when cutting, can stop stickation.

Vids might be hard to come by, chefs generally don't film bulk prep because they are busy (chefs in my kitchens were allowed to use phones for work but not play).

I think working on cutting techniques would be more beneficial than major knife modifications.

 

[stringer]

I agree with @stringer on this one. Stickation is minimized by better knife control. Micro adjustments, when cutting, can stop stickation.

Vids might be hard to come by, chefs generally don't film bulk prep because they are busy (chefs in my kitchens were allowed to use phones for work but not play).

I think working on cutting techniques would be more beneficial than major knife modifications.

Just using pull/draw cuts can be pretty fantastic for stuff like waxy potatoes.

 

[Jeff]

Apologies in advance for the dumb questions. I know the answers for these have been discussed already but for the life of me, I can't seem to find the right threads with the advanced search box (but have enjoyed reading the many other threads that I thought would tell me the answers ).
Okay, the back story here is I did all my Christmas prep with a 57mm tall nakiri, which (as far as I can tell) is a wide bevel flat V grind, and it got me wondering what I could do to tinker with it to try and improve the food release. That started my researching, which coalesced into the following questions:

1) Surface: Is there a generally agreed grit count for a sandpaper finish that is better (or less bad) for food release? Best that I could find from my research was that anything other than a high grit or mirror finish would promote less contact between wet product and the blade (it currently has a hairline / sanded finish so I'd only be tinkering a little bit to change the existing grit finish).

2) Convexity: Is there any effective way to incorporate convexity into an existing flat grind wide bevel that could improve food release? Here I'm ruling out a full convex regrind as I don't have the skills or a water cooled belt grinder, but intuitively it doesn't seem like I would benefit at all from rounding / blending the shinogi line with sandpaper would be worth while, as it may just make more product slide more easily up the height of the blade? Likewise, it doesn't seem to me like a higher bevel angle for the edge would make a material difference? Keen to hear any thoughts or opinions?

3) S grind: Rereading Kipp's fine threads on asymmetry and the hook grind thread, as well as some other threads on s-grinds, it kind of seems like an option that I would have would be to try and sand an air gap on the right hand side (I'm a righty) just above the shinogi line to try and interrupt the product in it's progression up the height of the blade? Is that even worth considering as an option? Has anyone toyed around with after market mods of this nature and any suggestions?

Thanks in advance!

What a great question!

I always forget whether one gets better release by oiling the blade or the product being cut!
(Yes, I am joking … Of course I remember it is always oil the knife blade or the food gets greasy.

Anyway, I bought a few Glestain knives to cut high starch or high stiction product.

They are not too expensive and I get amazing release on high starch product.

(I consider Russet Potatoes to be the best test of a knife’s ability to release product)


Glestains are asymmetrical. On a right hand version, there are 2 layers of grantons on the right side. The left side is slightly hollow ground and the edge is convexed at a 60/40 or 70/30 grind.

The down side is that it os sft steel an IMHO it does not hold a keen edge very long.

And as you can imagine it is a bit of a chore to sharpen (I am a system sharpener guy)

This is my “210 tater-hater! product just jumps off the blade!

I recently bought a Majime “feather” K-tip. It does not release as well as the Glestains

 

[NameAlreadyTaken]

Just using pull/draw cuts can be pretty fantastic for stuff like waxy potatoes.

Thanks Stringer! I’ve got some different approaches to try out.

 

[NameAlreadyTaken]

Thanks everyone for the feedback. Looks like I’ve got a few projects to work on. I’ll aim to report back (if I actually make things better, and don’t have my head hung in shame ) later…..

 

[mengwong]

You may see if the so‐called Kesselscher Walkschliff may help you. It's done by heavily rounding the spine, in fact, by reducing its width.

I might try this on one of my sujihikis, thanks for the suggestion! Or am I just making up an excuse to buy a Nanohone 100 …

 

[Benuser]

I might try this on one of my sujihikis, thanks for the suggestion! Or am I just making up an excuse to buy a Nanohone 100 …

I don't know anything about the Nanohone, but with the huge amount of steel that has to be abraded you may consider automotive sandpaper instead...