Edge retention - paper towel test

[JPAU]

I anticipate that this will vary based on steel, heat treatment, angle acuteness, type of use, board contact etc, but how long would you expect an edge to retain paper towel cutting abilities! Alternatively, how much use would you expect until a knife ceases to cut paper towel but is still sharp enough for regular kitchen duties?

I am able to get an edge that cuts paper towel after a progression through a SG500, SR2000 and sometimes (but not always) a SR6000. I strip / debur on each stone and then strop on a kangaroo leather bench strop. Sometimes I try gliding through cork. I have been practicing on a couple of W1 and W2 knives.

I have found that after 1 or 2 uses, the knife still cuts through paper towel. After 3 or 4 uses, they go from cutting hanging paper towel easily (straight cuts) to not being able to do so at all (or struggling). I am using a rippled, thick paper towel (pic attached). Stropping with edge trailing strokes on a kangaroo leather bench strop doesn’t restore the ability to cut paper towel. They still glide though pepper and tomato skins with ease and feel very sharp to the touch. They’re perfectly useable and still better than their factory edges after 5+ uses. The edge from that point is relatively stable, ie keeps cutting through skins etc easily.

Is this normal (as in, do you expect a knife to keep gliding through paper towel even after several uses l, inc. board contact) or is it an issue with how I am sharpening it (e.g. a bur related issue) or is it a steel / retention related issue?

 

[azn_knives_4l]

Interesting topic. I've never tried to quantify given the variability of kitchen knife use as even one clove of garlic can be anything from 10 to 50 cuts into a board and this is even before we try to account for how the user handles the knife. I'm keen on seeing the responses though!

 

[JPAU]

Interesting topic. I've never tried to quantify given the variability of kitchen knife use as even one clove of garlic can be anything from 10 to 50 cuts into a board and this is even before we try to account for how the user handles the knife. I'm keen on seeing the responses though!

I realise that it’s not practical to quantify - really my question is whether the inability to cut thick rippled paper towel after ~3-4meal preps after having cut it effortlessly when the edge was fresh is ‘normal’ or whether it is a sign that I need to improve an aspect of my sharpening or stropping technique.

 

[Barmoley]

I realise that it’s not practical to quantify - really my question is whether the inability to cut thick rippled paper towel after ~3-4meal preps after having cut it effortlessly when the edge was fresh is ‘normal’ or whether it is a sign that I need to improve an aspect of my sharpening or stropping technique.

I would say it is normal with the steels you mention and assuming average meal prep, whatever that is. Too many variables, but I wouldn't expect a paper towel cutting sharpness to last for very long with simple steels.

 

[JPAU]

Thank you!

Should I expect much better from Blue 2 or Blue 1 or Ginsan? I haven’t had the courage to sharpen my knives in those steels yet to test it.

 

[Barmoley]

Thank you!

Should I expect much better from Blue 2 or Blue 1 or Ginsan? I haven’t had the courage to sharpen my knives in those steels yet to test it.

Hard to say, do it and let us know. I would not expect much better from blue 2 or blue 1, ginsan possibly better, but how much better and how can you tell since no 2 preps are exactly the same. Besides the knives are different making you possibly use them differently on same tasks in addition to all the other number of variables involved. All you can realistically expect to see is if you sharpen different knives and use them for a long time than at some point you might be able to detect a general difference among different classes of steels in your use. Even then there is no guarantee that it is due to the steel and not geometry for example. If all you did was only cutting paper towels it would be easier, but still not fool proof as you would need to make sure geometry is the same and you sharpen the same and hardness is the same.

If you compare classes of steels, I would expect MagnaCut/4v/zwear class to be better than white2/1095 class and worse than 10v/k390/A11 class. How much better, no clue, but probably pretty well correlated to CATRA wear resistance results since paper cutting is mainly a wear resistance test.

 

[JPAU]

That’s very insightful! Thanks for all of those very reasonable observations. I am still learning a lot about sharpening and it’s great to check with some experts along the way!

 

[M1k3]

Thank you!

Should I expect much better from Blue 2 or Blue 1 or Ginsan? I haven’t had the courage to sharpen my knives in those steels yet to test it.

Ginsan/AEB-H will have better edge retention. It's carbides are harder and contain more of them, than Blue 1 or 2.

Even AEB-L has better edge retention.

 

[nopomo]

Try finishing edge-leading on the 2000 without stropping.

 

[cotedupy]

do you expect a knife to keep gliding through paper towel even after several uses l, inc. board contact)

In a word… no.

 

[JPAU]

In a word… no.

Thanks - appreciate the brevity!

 

[PPIIBBSS]

I realise that it’s not practical to quantify - really my question is whether the inability to cut thick rippled paper towel after ~3-4meal preps after having cut it effortlessly when the edge was fresh is ‘normal’ or whether it is a sign that I need to improve an aspect of my sharpening or stropping technique.

Absolutely normal. I take my higher-end stuff to JKI to get sharpened, and they definitely lose the "paper towel edge" after just a few meal preps. But the edge is still perfectly good for food prep for literally months of use. I personally spend more time cutting veg than paper, so I feel like that's what truly matters haha

 

[JPAU]

Absolutely normal. I take my higher-end stuff to JKI to get sharpened, and they definitely lose the "paper towel edge" after just a few meal preps. But the edge is still perfectly good for food prep for literally months of use. I personally spend more time cutting veg than paper, so I feel like that's what truly matters haha

Thanks! I totally agree. I just wanted to diagnose if there is a weakness in my sharpening causing this. As you know, I’m a complete novice! I’m conscious that good and bad habits are inevitably developing, esp while I’m still new to it. I’m trying to be quite introspective and honest with myself so that I develop / foster good habits, while also identifying and stifling bad ones.

 

[blokey]

Even stuff like S90V will loose that papertowel cutting edge after some use, it’s very normal

 

[mengwong]

I personally spend more time cutting veg than paper

Paper towel IS a vegetable!

Back to the grindstone

 

[mengwong]

Too many variables

Suggestion: for a control knife, don’t meal prep after passing the test, but just leave it exposed to air for the same amount of time. Because even oxidation can dull a (very sharp) knife.

 

[stringer]

Suggestion: for a control knife, don’t meal prep after passing the test, but just leave it exposed to air for the same amount of time. Because even oxidation can dull a (very sharp) knife.

Not even remotely the same rate of destruction as board contact. Especially for simple steels. I haven't really touched my "work kit" since the pandemic. Just doing more management/teaching stuff where I don't need a real kit so it sits there. I have pulled it out a couple of times when I needed it for something or another and everything is still HHT sharp. But one shift of real use on a board and I know that they won't be able to cut paper towel cleanly. At least not a long the whole length of the blade like after a fresh sharpening. A "touch up" can bring it back. But every "touch up" will last a little bit less time than the one before it.

 

[Ruso]

If you prep involves lot of acidic food, then the edge on a simple carbon will be “gone” in no time. From personal experience, blue 2 and AS fair better against acidic food but not I am not sure how this will translate to paper-towel test.

 

[JPAU]

Not even remotely the same rate of destruction as board contact. Especially for simple steels. I haven't really touched my "work kit" since the pandemic. Just doing more management/teaching stuff where I don't need a real kit so it sits there. I have pulled it out a couple of times when I needed it for something or another and everything is still HHT sharp. But one shift of real use on a board and I know that they won't be able to cut paper towel cleanly. At least not a long the whole length of the blade like after a fresh sharpening. A "touch up" can bring it back. But every "touch up" will last a little bit less time than the one before it.

What about use in hand on acidic products? Similar effect to board contact?

 

[JPAU]

If you prep involves lot of acidic food, then the edge on a simple carbon will be “gone” in no time. From personal experience, blue 2 and AS fair better against acidic food but not I am not sure how this will translate to paper-towel test.

I only just saw this after I commented. I think you’re right - had a similar experience with a carbon petty that I use to cut fruit in hand after meals (grapefruit, tart apples etc.).

 

[Barmoley]

Acid will corrode and weaken the very edge since we are dealing with very little steel. Board contact will exacerbate this effect since now you are applying impact to weakened steel. How fast this happens very much depends on the acidity of what you are cutting and how reactive the steel is. Low alloy steels will suffer the most and stainless will be affected the least. Something like MagnaCut, which is extremely corrosion resistant might not be noticeably affected at all. Zwear for example is almost stainless, but not quiet. Bottom line, for very corrosive environments you want corrosion resistant steels for best edge holding.

 

[azn_knives_4l]

Acid will corrode and weaken the very edge since we are dealing with very little steel. Board contact will exacerbate this effect since now you are applying impact to weakened steel. How fast this happens very much depends on the acidity of what you are cutting and how reactive the steel is. Low alloy steels will suffer the most and stainless will be affected the least. Something like MagnaCut, which is extremely corrosion resistant might not be noticeably affected at all. Zwear for example is almost stainless, but not quiet. Bottom line, for very corrosive environments you want corrosion resistant steels for best edge holding.

People will say it doesn't matter or whatever but razor research confirms corrosion is big for carbon steel edges.

 

[Barmoley]

People will say it doesn't matter or whatever but razor research confirms corrosion is big for carbon steel edges.

Corrosion is a factor in carbon steel razors. The most interesting article I read on the subject is this even though it talks about stainless steel razors. I even tried what the article suggests and it worked for me, problem is I don’t always bother, but when I actually tried the results were very impressive.

 

[Redwax]

One thing I'll say is that you can cut paper towel cleanly with some burrs but you will go from sharp to dull pretty quickly in this case. If your knife is still very sharp after a few meal preps but struggles somewhat with paper towel or tissue then that's normal.

 

[cotedupy]

Thanks - appreciate the brevity!

Haha! To expand a little bit...

The reason clean cutting paper towel is so tricky, is because it's soft, yet fibrous, and it's free hanging. And to do it your edge has to be very clean and very even, but like @stringer said - pretty much as soon as you hit a board that will start to go, because... boards are hard.

The type of edge that will cut paper towel well happens to be similar to the kind that will cut most food well. But it isn't necessary to have an edge at that level, and the reason for that is also because... boards are hard.

You don't cut food whilst holding it dangling up in the air, and the board massively increases the normal force of what you're trying to cut. Halving a bit of paper towel on a chopping board is dead simple. So trying to use free-hanging paper towel as a test of edge retention is at best - irrelevant.

Newspaper or cigarette paper is better, and (imo) tomatoes probably best of all. The difference between a knife that will go cleanly through those vs one that will drop paper towel, is probably going to be effectively unnoticeable in use.

---

None of which is to say that the premise of your original question isn't important. In fact I'd say that edge retention is the number one most important aspect of good sharpening. It's just that dropping paper towel is too high a level to gauge it by.

 

[Rideon66]

Listen to the guy above me. Steel type makes the biggest difference for me in how long it lasts though.

 

[Kawa]

Sometimes my knives don't cut paper towel very well after sharpening

and yet I can provide a meal that evening




yeah yeah, I still 'fail' sometimes

 

[JPAU]

Thank you @cotedupy @Rideon66

 

[mengwong]

We choose to […] do the other things not because they are easy, but because they are hard. Because that goal will serve to organize and measure the best of our energies and skills, because that challenge is one that we’re willing to accept.

—JFK
president and
paper-towel-cutting enthusiast​

 

[Delat]

Sometimes my knives don't cut paper towel very well after sharpening

and yet I can provide a meal that evening




yeah yeah, I still 'fail' sometimes

Yes, as long as my knife will at least start a cut and go a few inches then I'm good. But if the edge just bounces off and won't start the cut, then I'm doing something wrong. I test the entry point at several places along the edge just to make sure my edge is consistent, and sometimes I do find a spot or two where I did indeed do something wrong - usually laziness or inconsistency on my part.