What's important when you sharpen knives

[cotedupy]

I get asked a bit about paper towel cutting and how to get there, because I do it sometimes in videos when I'm testing out or showing off a particular stone. And each time I have to tell people that it's not actually particularly important or worth worrying about too much, the reason I do it is mostly because I use paper towel instead of stone holders and to clean up, so I always have it to hand.

What's more important in a well sharpened knife (imo) is: functional longevity, or edge retention. I did a little vid before Christmas, which I don't think I posted here, that had a very impressive paper towel cut at the end, but what I didn't know until after I'd started using it was that I'd left a very small wire edge on the knife, and it rolled on the board. That was not a good sharpening job despite looking cool in the video.

Here are a couple of other short vids; the first shows a Mazaki after putting it on my lovely new Rosy Red Washita, the second is the same knife after a week of preparing X number of meals, without touching up or stropping:

Now this is a good sharpening job, but it's not because of the first video, it's because of the second. The knife is Shiro2 and it does lose that final 10% of ultimate sharpness a little more quickly than A2, or particularly AS, but it doesn't matter that it can't go through paper towel any more. The fact that I can easily decollate Little Miss Dior in the magazine shows that's it's still happily good enough for use in the kitchen. I don't need to get out a stone, I don't need to lose more metal.

---

Anyhow, that's just my take. Perhaps other people see it differently and think the knife could do with a touch up at that point? But I just thought I'd say for anyone newer to knife sharpening: You shouldn't necessarily equate the sharpest edge with the best edge.

 

[miggus]

I did a little vid before Christmas, which I don't think I posted here, that had a very impressive paper towel cut at the end

You posted it somewhere, because I saw it and it haunted me ever since . Very impressive, I was very curious in how to achieve this. Luckily, this thread somewhat put that importance into perspective. Thanks for sharing and your great work!

It's very funny - I keep thinking "I will practice this for a few more months and then I'll know everything". Then I see people who are really good at it and keep learning new things. Handsharpening really is a journey, and an art, if you want it to be.

 

[RRLOVER]

After getting a Kramer many years ago it changed my perspective on sharpening...Before that knife I used to do lower angles to get the knife as sharp as possible and you would end up with a larger bevel but I feel a weaker edge...After studying the Kramer his bevel was very small and was done at a higher angle which felt like had better edge retention although not as keen...My perspective is I would rather have longevity on my edges than having the utmost keen edge....But everything is personal preference and experiments in learning.

 

[cotedupy]

You posted it somewhere, because I saw it and it haunted me ever since . Very impressive, I was very curious in how to achieve this.

Haha... I’ve probably done quite a few show-offy videos over time! But the particular one I was thinking of (which I don’t think I posted) was this one of a Shibata TT:




Normally paper tests are quite good at picking up deburring issues tbh. But it definitely failed there, as I rolled a very fine wire edge the first time I used it.

If I’d sacrificed a bit of ‘sharpness’ originally, with a microbevel or higher sharpening angle like mentioned above, it would’ve been a much better effort!

 

[noj]

If lucky enough to own a couple knives, you can have your priorities tailored. I generally like works great in the kitchen along with longevity. Of course, different edges and profiles work better for different tasks. As far as paper towel cutting, I use it sometimes if I am trying something different in terms of sharpening. That said, I often get more information from the sound of cutting thin newspaper.

 

[Choppin]

Agree. My sharpness assessment after sharpening is just feeling the edge lightly with by fingertips, running it over my fingernail to check bite, and checking visually for any remaining burr / wire edge. And then of course cutting stuff and seeing how long it remains sharp... In practical use you don't need paper-towel-cutting-sharpness.

 

[cotedupy]

That said, I often get more information from the sound of cutting thin newspaper.

This is a very good point to note I think. The feedback from cutting newspaper or magazine paper is easier to read than things like kitchen roll.

 

[Pie]

Too many times I have run into the wire edge issue. Things blow through paper towel in such a way that indicates I’ve created a wonderful consistent edge. A wire edge, that is.

I still like to sharpen my knives too often. Before prep I can’t stop myself from taking a couple swipes at whatever finisher is sitting there. Doing so gathers data about technique as well as the stone itself. I’m slowly getting more aware of what’s going on at the edge these days, fortunately.

I suppose the flip side of it is some knives I don’t sharpen enough - I rely on insane geometry with the MM, take bigger swings with the cleaver, or use the huge amount of extra edge with the yanagi. All things I lack confidence in sharpening..

 

[Choppin]

I still like to sharpen my knives too often. Before prep I can’t stop myself from taking a couple swipes at whatever finisher is sitting there. Doing so gathers data about technique as well as the stone itself. I’m slowly getting more aware of what’s going on at the edge these days, fortunately.

That doesn't sound bad actually. Assuming you are using a fine stone, it shouldn't remove much metal and it's a way to practice or keep your sharpening skills in check and also maintain the edges...

 

[HumbleHomeCook]

"What's most important when you sharpen knives?" In a word, consistency.

First though, in terms of post-sharpening edge checking, the most important thing is to pick a medium/method and try to be consistent about it. This builds an internal database to compare feedback of the check and how it applies in use.

My standard is receipt paper. I have it in abundance and it's thinner than other papers so a little more challenging without being so delicate it's frustrating just to use or giving unrealistic feedback.

I do however, often use paper towel. Slicing across grain on paper towel, and doing it cleanly and quietly, can be quite challenging and rewarding. But even some drag will still make a good kitchen edge.

The main points with either medium are the feel of the slice along the entire edge and the sound.

But, no matter what you use, it should just be one inspection tool in your arsenal. Visual and tactile edge inspections are also very important and combine with the cutting test to help you have a more complete understanding of your edge. These will help you pick up on remaining burrs that the cutting test alone may mask.

Also recognize that hair whittling, swirl cutting paper towel edges often will last about no real cuts with many steels and geometries so you need to choose your own return on investment.

Once you settle on a testing/inspection regimen, you have consistent analytics to test your methods. Next, at least for me, is to establish consistency in my methods. I think this is good advice for all budding sharpeners. Don't worry about compound angles, varied edges, this angle for this knife but that angle for the other and so on until much further down your sharpening road. Pick a good all round approach of 15ish degrees (which for me is pretty natural) and just run with it on everything and along the entire edge.

Now you have consistent testing and sharpening inputs and from here any deviations (intentional or otherwise) as well as edge performance can be compared to each other and your past internal data base. This is much easier with fewer knives really. This will help you understand things much clearer and help you make good informed choices for your knives, your usages, and your expectations.

For example, I can pull out an 8k stone and good leather strop and develop a glistening edge my eye can see with a thinness and smoothness my fingers and thumbnail can feel and that then slides smoothly and quietly through paper towel. Mmmmm... now that's sharp. Then use it and feel it sliding off half my ingredients and realize I don't like that feeling. What changed? Oh, I went to higher grit and more stropping. Drop down to 2k and minimal, if any, off stone stropping. Not as shiny and feels more ragged. Cuts the medium well but a little louder but the edge performs great in all my tasks. I made a change and saw an effect. Process control. Oh no, my engineer is showing...

Still though... I mean it is good advice.

 

[Legion74]

Do you run your edge through anything to try and wipe the wire edge off?

I've taken to running the edge a few times through a champaign cork, before finishing with a few light X strokes on the stone and maybe a strop.

Judging from the notches cut into the end grain on some of my antique wooden hone boxes, the old timers did it on there.

Seems to work for me.

 

[HumbleHomeCook]

Do you run your edge through anything to try and wipe the wire edge off?

I've taken to running the edge a few times through a champaign cork, before finishing with a few light X strokes on the stone and maybe a strop.

Judging from the notches cut into the end grain on some of my antique wooden hone boxes, the old timers did it on there.

Seems to work for me.

Me personally no. I've played with it and never took to it. These days I focus real hard on stone-top burr removal.

 

[cotedupy]

Do you run your edge through anything to try and wipe the wire edge off?

Only very occasionally, and mostly on stainless.

Somewhere I've got a video of a knife that I drew the edge through a block of camphor wood about 50 times and it still cut a hanging hair afterwards, so I can say with a decent amount of certainty that there's very little loss of 'sharpness' doing that kind of thing.

Visual and tactile edge inspections are also very important and combine with the cutting test to help you have a more complete understanding of your edge.

Funnily enough visual inspection is one thing I thing I never do, dunno why, just never have. I use touch, thumbnail and paper towel.

My initial post perhaps sounded a bit like I was dissing paper towel cutting, but I didn't really mean to. In fact an edge (assuming you've properly deburred it!) that wings effortlessly through paper towel should actually be top-notch for kitchen use ime. It needs to be fine but still with bite, the reason paper towel is difficult to cut is the same reason that tomatoes are, so you do need teeth for it.

 

[cotedupy]

Though if I may be allowed to point out a thoroughly silly sharpness test, I give you: sideways tomato slicing, which is a bit of a cheat or illusion that plays on how friction works...

The reason that slicing a tomato downwards on a board is sometimes difficult is because the tomato is soft and so you have a very low Normal Force exerted upwards by the board against the knife.

But if you slice one sideways the Normal Force isn't coming upwards from the board, it's coming against the knife from the side and it's the result of the coefficient of friction between the board and the tomato. And that's quite high because the halved surface of the tomato is wet and the board is wood and grippy. Ergo it's quite easy to cut.

Try doing it with a carrot and you'll see the opposite: much easier to slice downwards because the carrot is hard, difficult to slice from the side because it doesn't stick to the board.

 

[Legion74]

Though if I may be allowed to point out a thoroughly silly sharpness test, I give you: sideways tomato slicing, which is a bit of a cheat or illusion that plays on how friction works...

The reason that slicing a tomato downwards on a board is sometimes difficult is because the tomato is soft and so you have a very low Normal Force exerted upwards by the board against the knife.

But if you slice one sideways the Normal Force isn't coming upwards from the board, it's coming against the knife from the side and it's the result of the coefficient of friction between the board and the tomato. And that's quite high because the halved surface of the tomato is wet and the board is wood and grippy. Ergo it's quite easy to cut.

Try doing it with a carrot and you'll see the opposite: much easier to slice downwards because the carrot is hard, difficult to slice from the side because it doesn't stick to the board.

I quite like the old tomato drop as a pure measure of sharpness (though probably impractical sharpness for the kitchen). Because a falling tomato comes straight down, the tooth has no sawing power, so it’s all about the apex and the thinness behind the edge.

 

[Jovidah]

I just test on my armhair... if it shaves decently it's good to go. As long as you don't sharpen too often armhair is a plentiful, replenishable and sustainable resource.

 

[cotedupy]

I quite like the old tomato drop as a pure measure of sharpness (though probably impractical sharpness for the kitchen). Because a falling tomato comes straight down, the tooth has no sawing power, so it’s all about the apex and the thinness behind the edge.

And then of course we have the renowned 'Blueberry Test'. A demonstration not merely of the knife's edge, but also the supreme accuracy of the spitter...

 

[KingShapton]

These days I focus real hard on stone-top burr removal.

 

[Benuser]

This is a very good point to note I think. The feedback from cutting newspaper or magazine paper is easier to read than things like kitchen roll.

Same here with cigarette paper.

 

[stringer]

Here is my mindset:

Scrubbing motion is for the blade road / wide bevel / behind the edge thinning / damage repair only.

Sharpening the edge I use edge leading full length alternating strokes with gradually diminishing pressure and particle size.

The final cutting edge is a convex micro bevel that finishes at a slightly higher angle to improve durability and food release and ensure proper burr removal.

Everything else is extraneous.

 

[Desert Rat]

My wife came home with a thirty some odd pound bone in rib roast the other day. I grabbed a boning knife and a workhorse gyuto out of the block and started reducing it into steaks. I don't remember what I last used to finish that gyuto but it sucked. Sharp it was when I first started though, a highly refined edge.
I grabbed a tri hone that had a fine India in it and used a good amount of pressure, a couple minutes later I had an edge that breezed through the task at hand. That edge wouldn't have impressed anyone in a sharpness demonstration. But it was just what I needed and wanted.

So what I'm saying is what's important in sharpening is a moving target, dependent on knife and task.

 

[M1k3]

My wife came home with a thirty some odd pound bone in rib roast the other day. I grabbed a boning knife and a workhorse gyuto out of the block and started reducing it into steaks. I don't remember what I last used to finish that gyuto but it sucked. Sharp it was when I first started though, a highly refined edge.
I grabbed a tri hone that had a fine India in it and used a good amount of pressure, a couple minutes later I had an edge that breezed through the task at hand. That edge wouldn't have impressed anyone in a sharpness demonstration. But it was just what I needed and wanted.

So what I'm saying is what's important in sharpening is a moving target, dependent on knife and task.

I use a fine India pretty regularly. Great tomato and fatty stuff cutting edge.

 

[Benuser]

Here is my mindset:

Scrubbing motion is for the blade road / wide bevel / behind the edge thinning / damage repair only.

Sharpening the edge I use edge leading full length alternating strokes with gradually diminishing pressure and particle size.

The final cutting edge is a convex micro bevel that finishes at a slightly higher angle to improve durability and food release and ensure proper burr removal.

Everything else is extraneous.

I like light scrubbing with an intermediate stone, as a NP800. FWIW, I believe it avoids bad surprises with burrs detaching only with finer ones. I'm not always that certain to have achieved a complete deburring on the first stone, a SG320 or NP400. After the scrubbing, I deburr with short edge leading strokes in sections, enough to abrade, but not that long that a new burr got raised. With finer stones, only very light edge leading strokes. I'm looking for some refinement, but not necessarily a full polish. Otherwise, as a home user I don't have them to withstand the demands of a professional kitchen, with long shifts, abusive colleagues and poly boards. Only exceptionally using microbevels as I find their touching up far from simple.

 

[kayman67]

After getting a Kramer many years ago it changed my perspective on sharpening...Before that knife I used to do lower angles to get the knife as sharp as possible and you would end up with a larger bevel but I feel a weaker edge...After studying the Kramer his bevel was very small and was done at a higher angle which felt like had better edge retention although not as keen...My perspective is I would rather have longevity on my edges than having the utmost keen edge....But everything is personal preference and experiments in learning.

They aren't mutually exclusive, but there's always more accessible cutting performance (well, somewhat more accessible as thinning is involved sooner or later and might have its own challenges) with a very thin blade and a microbevel (high pass as I call it sometimes just to hint that's done at higher dps). The reason behind this is that less effort is required to cut thus less stress is induced and you multiply that in a non liniar increase. This would work either way, but in practice it's just (so much) easier to obtain a good thin edge/high pass micro bevel combo, compared to the level of consolidation a very low dps would require. Provided you have a thin edge and provided the alloy would fully allow a very low dps to begin with. But, for example, ZDP-189 did tremendously well with very low dps. It's still silly just how many shifts this performs so well, done over several blades, with under 10 dps (dps is degrees per side, not all inclusive). I always consider edge retention and thus the sharpening job (better called edge development maybe), based on long term performance. I've seen just to many times extremely sharp edges that would have like a clean 10 BESS score or whatever and would just dissappear almost entirely even in seconds, that I am not impressed when someone would demonstrate this right after sharpening. Tricks after sharpening are, of course, always fun, but I want to see how the blade is after some good usage.
So what exactly is important while sharpening? There might be a few things that we don't talk very much about or as much as we should in general, even before sharpening. In no particular order, but some of the first things to consider. To determine the usage of a particular blade. In other words, to imagine first the usage scenario and later find the limits the blade has for that particular usage scenario and see just how we could do things to perform better. Also, to consider alloy/abrasive interactions. These do have an impact on overall edge quality and ultimately retention, more than usually accepted. We can't really apply the one fits all rule and expect to get best results across the board. The further we go after best possible performance, the further we need to look into specifics. Law of diminished returns will eventually apply, but it's not universal at a fixed point. Experience is key not to over do things, but also to adjust and do them as good as possible, using the knowledge, skills and tools available.