Effect of Chopping Board Material on Edge Longevity

Good work. You are going to make a lot of fancy cutting board makers cry. You also exposed a myth or two about what makes a good cutting board.
thanks
the old sailor
 
Thank you.

This is very timely as I was considering one of those Japanese boards but just couldn't convince myself that it mattered that much.

Always enjoy your posts.
 
I saw this over at kitchenknifeforums.com when Scott started a thread over there. Thank you for posting the video and the PDF. I had this to say over at KKF so I just copied it over here and would love to see your comments in reponse.

THE GLASS CUTTING BOARD SHOWED AN INCREASE IN SHARPNESS THROUGH THE FIRST 400 TEST SLICES!

Look at the actual data and you'll see things that don't seem to make sense. I copied their data and made the following graphs from it.

yy779jQ.jpg

From the graph above, you can see the sharpness (remember LOWER number = GREATER sharpness) after slicing on glass actually INCREASES during the first 400 slices. Excluding the outlier at 400 cuts, bamboo even shows increased sharpness through the first 1000 cuts!



DGGMYTn.jpg

Ok, how about the acacia wood edge grain versus end grain? From looking at just the starting sharpness versus the ending sharpness after 2000 cuts, what they show in the table on page 5, the sharpness gets better going from 125 to 115 for edge grain (long-grain in their words) or 130 to 110 for end grain. But the actual data shows a trend that seems to say they get duller through the first 800 cuts but then start to get sharper again!

Also, take note that the initial sharpness of the knives tested ranged from 120 to 195, so we are not comparing apples to apples to begin with.

The upshot to me is that there are some problems with measuring sharpness in their experiment. The data seem to show there may be errors in the precision of the measurement and/or errors in the accuracy, most likely both from the scatter and trends seen. The data given were averages of three readings, so we have no access to the raw data, only the averaged data. However, you can see that the sharpness seems to go up and down willy nilly. For example the acacia end grain sharpness swings up and down over a range of 35 points (120 to 155) through the first 600 cuts. Is the knife actually getting sharper then duller and then sharper and then duller again? It's possible... but not likely; therefore, it's more likely a problem with the sharpness measurement.

Looking at the sharpness testing apparatus and the manufacturer website, it looks like you cut a piece of test media (looks like some sort of plastic thread) which is threaded into a holder. Inconsistency of the test media could lead to scatter. Inconsistency with the tension applied to the media when strapped into the holder could also lead to scatter.

All in all, from the data the conclusion I would be willing to draw is that there may be some dulling when cutting on tempered glass, but otherwise the data is not of high enough quality to otherwise draw many conclusions. Multiple data points on each cutting board should be made, i.e. multiple knives tested per cutting board material versus just one knife per material, and perhaps multiple (more than the 3 used in this experiment) sharpness measurements per data point.
 
milkbaby said:
Looking at the sharpness testing apparatus and the manufacturer website, it looks like you cut a piece of test media (looks like some sort of plastic thread) which is threaded into a holder. Inconsistency of the test media could lead to scatter. Inconsistency with the tension applied to the media when strapped into the holder could also lead to scatter.
Click to expand...
Read a bit about the tester and the test medium https://www.edgeonup.com/ and see how they have tried to eliminate test media and tension as a factor in their testing.
 
scott.livesey said:
Read a bit about the tester and the test medium https://www.edgeonup.com/ and see how they have tried to eliminate test media and tension as a factor in their testing.
Click to expand...

Do you have the specific link to the factors involved? The only thing I could easily find were the instruction manual that says to load the test media without slack under slight tension but not too much tension.

From the support document (https://www.edgeonup.com/Support_Document.pdf) , it shows the test media is 0.009 inch in diameter and that chipped and rolled edges gave a variation in sharpness measurement from 45 to 60 points. So if we say the error in the measurements is plus or minus about 25 to 30 points, then to get high quality data to draw conclusions from, many more than three measurements per knife at each number of cuts should be made to get a measurement that truly reflects sharpness. This would be in addition to using more than one knife per cutting board material.

Looking only at the data points provided (which are averages of three measurements), the only conclusion that I feel is well supported is that the tempered glass appears to dull the knives most. There may actually be a burnishing or polishing effect going on, but I don't think the data set is high enough quality to 100% support that conclusion.
 
I got a little lost when you started using units of applied moments (Newton-meters) for force, which should be in Newtons. What is the moment arm that's being used here?

It seems like you're just resting a 2 kg mass on the spine of the blade using a roller, which means you have an applied force on the spine of 19.6 Newtons. No moments come into play here.

Next, is the data indicating that the test knife gets sharper after the test cuts? I think this suggests that you might need to run more trials, or develop your sharpening techniques, as prolonged sliding contact with a cutting board should probably not be refining your edge.
 
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marrenmiller said:
I got a little lost when you started using units of applied moments (Newton-meters) for force, which should be in Newtons. What is the moment arm that's being used here?

It seems like you're just resting a 2 kg mass on the spine of the blade using a roller, which means you have an applied force on the spine of 19.6 Newtons. No moments come into play here.

Next, is the data indicating that the test knife gets sharper after the test cuts? I think this suggests that you might need to run more trials, or develop your sharpening techniques, as prolonged sliding contact with a cutting board should probably not be refining your edge.
Click to expand...
what they found was average force needed to slice selected items was duplicated with a 2 kg mass. Read the entire article. They also had some ideas as to why sharpness may increase. The authors run a commercial sharpening service in Oz.
To cut to the chase, the authors found that needing to use an end grain board to protect you knife edge may just be good marketing and not based on repeatable science.
more information here: http://bessex.com/forum/showthread.php?tid=50
the old sailor
 
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Keep in mind thst even with edge grain boards, the slice can be in-line with grain, perpendicular to grain or oblique (at an angle).

(At work, so havent read entire report yet...)
 
scott.livesey said:
what they found was average force needed to slice selected items was duplicated with a 2 kg mass. Read the entire article. They also had some ideas as to why sharpness may increase. The authors run a commercial sharpening service in Oz.
To cut to the chase, the authors found that needing to use an end grain board to protect you knife edge may just be good marketing and not based on repeatable science.
the old sailor
Click to expand...

I did read it. They placed a 2 kg mass on a roller and compared it to an applied moment, which doesn't make any sense in this context, nor are they being careful to differentiate between moments and forces. I have a background, degree, and professional license in mechanical engineering and am still confused as to what they are trying to communicate by using the terms. I'm fine with the idea of the roller applying a load to the knife, but I'd like to understand what on Earth they're referring to with their language.

I saw they suggested why the edges might become more sharp with applied cutting. Not only is this completely contrary to my own experiences making, sharpening, and using kitchen knives, but it flies in the face of what one might expect given the fact that the knife edge is wearing along the cutting board the entire time. It's not impossible, but one should demand a lot more trials and testing before accepting such claims. The fact that their data is just all over the place should be an indication that waaaay more trials are needed, if not better control over the testing.

Further, those sharpness tests are not entirely repeatable, from what I've seen of people testing them, and the margin of error for them should indicate a bunch of tests being a requirement before any conclusion can be drawn. I saw no indication that this was the case, and that wasn't helped by the article being beyond confusing to interpret.
 
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Our goal was to separate edge-friendly boards from edge-dulling. For my sharpening business we need firm facts to advise our customers.
The takeaway of this study is that edge-dulling boards are there, and we can name 3 of them.
By design, this study cannot tell which of the edge-friendly boards is better; within the frame of the study they are all OK, no winners, no losers.

It goes without saying that there is more to a cutting board than just not dulling your edge - looks and feel matter.
As I was struggling with my wife and mother to replace their beloved cutting board that showed badly in the test, I realized that for some the beauty and longevity of the cutting board mean more than sharpness of their knives...

As to the BESS sharpness tester.
When 3 years ago I was looking for a sharpness tester, I found a well-thought one by New Zealand Anago developed by Peter C. Dowd, but it was the BESS sharpness tester affordability and BESS sharpness standard that attracted me.
We have no CATRA sharpness tester for rent in Australia, as you have in the USA. CATRA sharpness testers cost $50-100,000 depending on the model, the NZ Anago about $20-30,000, while the BESS tester $300 delivered.

As to the testing load.
It was clear to us that the load on the knife should be within forces used in natural cutting, if we want meaningful data.

When you repeatedly press on the BESS sharpness tester scales, it does not add the numbers, its software remembers the highest number and shows it on the display. How we used this feature in estimating the sliding cut load is shown in our video. The sliding cut has no torque of course, and is not measured in Newton-meters; the most appropriate unit is kg-force.

Chopping force is measured by moment in Newton-meters, as are many cutting motions. The meat plant research on forces in meat cutting that I mentioned in the article was done in New Zealand, not by us, and can be viewed here:
http://knifegrinders.com.au/dropbox/Cutting_moments_in_meat_cutting.pdf

These two estimates told us that the 2 kg load on our stand should more or less represent the natural cutting load at its peak.

I understand all the limitations of the testing we did, but better little firm facts than none at all. I am not aware of other sharpness tests done on cutting boards, aside from a funny one sponsored by the board seller.
 
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wootzblade said:
Our goal was to separate edge-friendly boards from edge-dulling. For my sharpening business we need firm facts to advise our customers.
The takeaway of this study is that edge-dulling boards are there, and we can name 3 of them.
By design, this study cannot tell which of the edge-friendly boards is better; within the frame of the study they are all OK, no winners, no losers.
Click to expand...

That's the thing. The quality of the data we're looking at should make that a hard position to take. Regardless of what one might think about the various cutting boards, the fact that the knife got sharper for the first 400 (!!!) cuts on a glass cutting board with roughly 20N of force applied to the back of the blade should be an indication that something is wrong. Then it measured dramatically duller, then sharper again, then duller, then sharper, etc. There's no consistency to this data. You might as well have flipped a coin.
 
wootzblade said:
Chopping force is measured by moment in Newton-meters
Click to expand...

No it is not. They are referring to a moment (force x distance) on the handle from the force on the cutting edge. This can be related to the loads on a human hand and body when using the knife for certain cutting tasks, which seems to be the topic of said article. Those are two different, but related, concepts. You might have calculated a decent value for the force on the knife based on the moment, but conflating the two is needlessly unclear. Just say you applied a force to the spine of the blade with a roller, list the force in Newtons or kg-force, and be done with it.

And that is far, far less of a big deal than the elephant in the room, which is the data consistency.
 
Factory edges usually show some variance in sharpness scores for obvious reasons.
Comparison of the factory edge to resharpened is in the article, showing greater variance in the factory edge. As is the explanation why we used the factory-sharpened knives out of the box, not the resharpened.
 
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I read your PDF study, very well done, thanks for your efforts!

Question now is, which are great HD-propylene chopping board buys on the international market? Brands, models. Maybe i can buy 1 for my moms!

wootzblade wootzblade and what about high density polyethylene, something like HD-PE-500 ?
 
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