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View Full Version : Polished vs. toothy edges



dannynyc
06-18-2013, 02:06 PM
The common (though not unanimous) wisdom out there seems to be that a highly polished edge will last longer than a toothy one. Can someone explain why this would be so. And does anyone disagree? Assuming it's true, is the difference significant?

Also, has anyone had luck with a very highly refined edge going through tomatoes easily (as opposed to a toothy one, which many seem to think works better for tomato skins).

ThEoRy
06-18-2013, 02:27 PM
Different edges for different knives. Yanagi = polished, gyuto = toothy. GYuto is for a variety of products and cutting techniques so it needs a toothy edge in order to perform well. Yanagi is made for slicing raw protein so a polished edge will make cleaner slices and last longer. A polished edge on a gyuto doesn't last long at all.

dannynyc
06-18-2013, 02:35 PM
A polished edge on a gyuto doesn't last long at all.

I'm sorry, but that doesn't make any intuitive sense to me. Clearly you don't mean there is anything about the shape of the gyuto (vs. e.g., a yanabi) that would make this so. Are you saying that because gyutos have to tackle many different types of foods, it is likely to have an edge that doesn't last as long as a single-purpose knife like a yanagi? If so, it doesn't logically follow that a polished edge wouldn't last as long as a toothy one.

I'm not saying I disagree with you (you clearly know more than I do, and I'm coming into this knowing nothing), but I'm not following your explanation.

Brad Gibson
06-18-2013, 02:38 PM
I find when I polish my gyutos to mirror finishes they literally lose degrees of sharpness with each board contact or rough contact with even a vegetable. I prefer about 5k finish on mine. My vg10 lasts longer than my white #2 when polished as well. I strop my slicers super high always. They don't get as much board contact so their delicate edges can stay sharp for longer.

These are just my thoughts. I'm pretty much a novice web it comes to this stuff but..:2cents:

ThEoRy
06-18-2013, 03:00 PM
Gyutos have more board contact and have to cut through many different products with many different cutting techniques. Yanagi are only used it one direction through raw product. It has nothing to do with the shape. It's all about the product and technique. From experience I can tell you highly polished edges on gyuto fail near immediately upon use. Sure it's sharp as hell the first use, but it won't last at all.

Brad Gibson
06-18-2013, 03:05 PM
Gyutos have more board contact and have to cut through many different products with many different cutting techniques. Yanagi are only used it one direction through raw product. It has nothing to do with the shape. It's all about the product and technique. From experience I can tell you highly polished edges on gyuto fail near immediately upon use. Sure it's sharp as hell the first use, but it won't last at all.

:plus1: agreed

keithsaltydog
06-18-2013, 03:10 PM
Gyutos have more board contact and have to cut through many different products with many different cutting techniques. Yanagi are only used it one direction through raw product. It has nothing to do with the shape. It's all about the product and technique. From experience I can tell you highly polished edges on gyuto fail near immediately upon use. Sure it's sharp as hell the first use, but it won't last at all.

Agree Yanagi's polishing stone,Gyuto's Med. stone between 1K & 2K,Sliced & Diced many cases of tomato's for Lomi Salmon wt. a Med. toothy edge.

DevinT
06-18-2013, 03:47 PM
The coarser something is sharpened, the longer the edge will last.

A polished edge is better for push cutting and a toothy edge is better for slice cutting.

Hoss

ThEoRy
06-18-2013, 04:18 PM
Devin makes an interesting point about the teeth. Think of it this way, under a microscope the teeth would look like a saw blade. The longer the teeth are the longer it takes to abrade them down to dull. If the teeth are very fine or refined/polished they are smaller so there is less material to wear away before reaching the dull state, so it happens faster.

dannynyc
06-18-2013, 04:27 PM
Devin makes an interesting point about the teeth. Think of it this way, under a microscope the teeth would look like a saw blade. The longer the teeth are the longer it takes to abrade them down to dull. If the teeth are very fine or refined/polished they are smaller so there is less material to wear away before reaching the dull state, so it happens faster.

Now THAT makes sense.

zitangy
06-18-2013, 05:54 PM
Now THAT makes sense.


This is one of the reasons that i reckon that it will be better not to overpolish with each grit and leave multiple grit striations on an edge..

The courser grit will leave a higher striation will be hte first to go (?) as it is higher and more direct contact with teh food and then the finer grit striation will be the next to go and the finest grit being the smallest striations will be the last line of defence. UNless, the coarser striations folds over the finer striation and render it toothless.

Logically say if it is over polished on say the 10,000 grit, the edge can be taken finer/thinner as the stone is finer provided of course that the steel is also fine grained and will thus roll/ fold over quicker than the thicker edge from a not so fine stone.

Havent figured out why courser grit will be better for push cut. Has it got anything to do with the angle of the striations/ teeth in relation to the edge? CLd it be that most people sharpen the knives to stone at 60 degrees ( there about) as it is an instinctive angle as it is more comfortable and natural?

just my thoughts..
d

keithsaltydog
06-18-2013, 08:15 PM
Murry Carter talks about striation direction in his Advanced Sharpening DVD.Japanese Sushi Chefs are said to sharpen at a angle usually polishing stones to give a striation that favors the slicing action of a Yanagi cut.He also talks of the theory of a master Japanese sharpener that leaving some mud on the stone not only aids in sharpening process,but also causes abrasion in all different directions that adds durability to the edge.

ThEoRy
06-18-2013, 09:19 PM
With natural stones grit range varies and changes when it further refines in the mud. This causes teeth of many different sizes which abrade at different rates causing the edge to last longer.

panda
06-18-2013, 09:40 PM
Gyuto, aim for that fine line between toothy and polished, a balanced edge. I find my latest stone very capable in that department
JNS synthetic aoto, I have no idea what grit it is but I sharpen on it starting with moderate pressure and finish with light touches. Jks 3k stone works in this manner as well, I imagine the two stones I mentioned are around final 4k edge.

Justin0505
06-18-2013, 09:50 PM
as zitangy already mentioned: I've found that you can get a good combination of the benefits of toothy and polished by moving up the progression in stones before completely removing the scratches (teeth) from the coarser stone. Funny that you can get a "better" edge by using fewer stones, bigger gaps in grit, and spending less time on the later ones.

andre s
06-18-2013, 11:11 PM
On certain knives (gyutos in particular come to mind), different parts along the edge tend serve different functions. I wonder if there would be any benefit to varying the level of polish/toothiness along the length (e.g. tip vs heel). Realizing that this would probably go against most proper (full stroke) sharpening techniques, I wonder if anybody here has experimented with that?

panda
06-19-2013, 12:09 AM
varying edge along the length of the blade would drive me nuts!!

tk59
06-19-2013, 01:43 AM
as zitangy already mentioned: I've found that you can get a good combination of the benefits of toothy and polished by moving up the progression in stones before completely removing the scratches (teeth) from the coarser stone. Funny that you can get a "better" edge by using fewer stones, bigger gaps in grit, and spending less time on the later ones.+1. With regard to sharpening different parts of a knife different ways, some people do it, esp. if a knife is task specific and the task has two distinct parts. Deba sharpening comes to mind.

Zwiefel
06-19-2013, 09:11 AM
Happy 4000th post TK59!

NO ChoP!
06-19-2013, 11:43 AM
I've been saying all along; since 10, 12, 16 and 32k stones were the fad; since .0025 micron strops;

A rugged, well rounded gyuto edge lies between 2 and 6k tops. Anything above is just silly, "let me push cut this tomato one time" antics.

I'm glad people are coming to there senses.

I must say, I've always been very conscience about well aligned scratch patterns; this whole different patterns leads to more toughness thing is gonna have to be tested...

zitangy
06-19-2013, 12:04 PM
With natural stones grit range varies and changes when it further refines in the mud. This causes teeth of many different sizes which abrade at different rates causing the edge to last longer.

Hi..
a)I am just wondering as to whether the synthetic material from stones do also eventually break down due to attrition . Are they more resistant?

b) It is also fr this reason that I use say a 3,000 grit stone to clean or create mud on say a 5,000 grit stone. Grit contamination does replicate the desired mixture.ON this subject, the texture of the mud becomes relevant.... too watery not much slurry around. Too dry, it cant do its job. A right amount of water ( droplets, via a spray) will have the right mix and texture.

Look forward to the above said confirmation.

D

Patatas Bravas
06-19-2013, 02:18 PM
Hi.. a)I am just wondering as to whether the synthetic material from stones do also eventually break down due to attrition . Are they more resistant?

More resistant? Yes. Break down? Apparently no.

The source may be a nat-stone seller, but I'm a believer and I think this was also written by another member here. Easy to find info: http://www.japanesenaturalstones.com/JNS-Grit-Fines-and-Hardnes-s/1835.htm

Editted quote:

Japanese Natural stones do not have grit like we see in synthetic ... they have flakes. These flakes will release at different rates and patterns depending on how hard or compact the stone ... these flakes will continue to break down ... if you take synthetic stones, the particles are cubed or rounded with extremely sharp edges ... These particles will deeply gouge ... leaving deep and difficult to remove scratches. Synthetic stones are also produced by grit being super-compressed into a hard resin or ceramic binder, the particles break off in huge, non-friable, chunks and stay suspended in the slurry as you sharpen. This results in very fast metal removal, but also contributes to the deep gouging ...

Patatas Bravas
06-19-2013, 02:24 PM
... A follow-up point to the above is that I think synthetic stone sharpeners will wear down their knives a lot faster than nat-stoners. I wonder about this when I read posts for example on BST where a knife might have been '55mm at the heal, but now 52'. I usually imagine there's been too much sharpening, or too much harsh synthetic sharpening.

dannynyc
06-19-2013, 02:26 PM
An interesting observation that gets back to my original point -- there seems to be near-unanimity here that toothy edges last longer than polished ones. But some searching around the internets shows that there are plenty of people on other forums who say the opposite.

wsfarrell
06-19-2013, 02:35 PM
Here's a quote from Alex at The Japan Blade which amplifies Maxim's comment about how natural stones work. This is the bible for me.
------------
Natural sharpening stones, the type found near Kyoto but also in other parts of Japan, are complex in their material make up and contain tens if not
hundreds of different elements and compounds. Some of the minerals and fossilized organic material act as cutting and polishing agents while
some make up the binder portion of the stone that holds everything together. The harder minerals like chert, a form of flint, do most of the cutting
while clays mostly make up the binder. Users of Japanese stones notice the contrast between the hard steel and the soft iron after sharpening, in
Japan this is called Kasumi. Kasumi is a word that describes the fuzzy or hazy look objects take on when viewed over hot summer ground. The
kasumi look is desirable to most Japanese tool users but few understand how this effect is achieved.

Taking into account the hardness of these blades, in the Rockwell 60-65 range, only a fraction of the available abrasive grit mix in these stones will
actually polish the hard steel cutting edge, the clay certainly will not. But conversely because the iron backing on laminated blades is so soft almost
every thing in the grit mixture will affect the polish of this softer iron material, even the softer flakier grit particles.

During the sharpening process the soft iron has been honed and reduced in mass by the effects of all of the grinding compounds working in
unison. The chert which cuts the soft iron like butter and the clays, salts, radiolarians and even some silica that is a know element of some of the
older wrought irons will help to sharpen or reduce the jigane soft iron as it is coaxed out of the iron base. The kasumi effect is basically the result of
all of these lesser abrasives working together to sort of massage the surface of the iron, none of the abrasives acting on their own to over power
the other, a little bit like Judo, which translates as "the soft way". The iron is changed and reduced and sharpened, but in a soft way.

The hard tool steel takes on a polished mirror look, some suggest it has the look of chrome. This microscopic scratch pattern in the hard steel that
makes it look polished has been cut by only the hardest of the hard abrasive particles and it looks regular and finished. The soft iron on the other
hand looks dull and complicated. This is the contrast in the polish that is achieved with the natural stones. Synthetic stones give an over all highly
polished bevel while the natural stones allow the soft iron to look soft.

Patatas Bravas
06-19-2013, 02:47 PM
Devin makes an interesting point about the teeth. Think of it this way, under a microscope the teeth would look like a saw blade. The longer the teeth are the longer it takes to abrade them down to dull. If the teeth are very fine or refined/polished they are smaller so there is less material to wear away before reaching the dull state, so it happens faster.

I agree. However, if you imagine two toothy edges, one coarser and one finer, and if the teeth of both have been worn away the finer edge will still remain the sharper because it's still going to be thinner, no?

Zwiefel
06-19-2013, 02:54 PM
Excellent write up, thanks!

maxim
06-19-2013, 02:57 PM
To be honest i have never seen a huge difference in toothy VS polished in edge holding, however i seen more bight in toothy edge like on cutting tomatoes.

For slicing i really dont want to use toothy edge, if you slice something like fish or fine vegs you want that shine to it that you can only make with polished edge


The hard tool steel takes on a polished mirror look, some suggest it has the look of chrome. This microscopic scratch pattern in the hard steel that
makes it look polished has been cut by only the hardest of the hard abrasive particles and it looks regular and finished. The soft iron on the other
hand looks dull and complicated. This is the contrast in the polish that is achieved with the natural stones. Synthetic stones give an over all highly
polished bevel while the natural stones allow the soft iron to look soft.

That also may be Not true, because i can make very good Kasumi finish on Synthetic stones :) And also very good mirror on Jnats '
Mud control is the most important in Kasumi finish

bamin
06-21-2013, 04:21 PM
Never tried this, but what if you sharpen to a very polished edge and then put a micro-bevel on with a coarse stone? Would that have any kind of benefit or make a difference?

JBroida
06-21-2013, 05:33 PM
not really... its the same as sharpening on a coarse stone in general

Chefdog
06-21-2013, 05:44 PM
Bamin,
What some do to kind of bridge the gap between toothy and polished is to drop down one stone (say from 8K to 2-3k) after polishing and strop a couple times on the coarser stone to add some bite to the edge.

Patatas Bravas
06-22-2013, 03:01 PM
Never tried this, but what if you sharpen to a very polished edge and then put a micro-bevel on with a coarse stone? Would that have any kind of benefit or make a difference?
not really... its the same as sharpening on a coarse stone in general

Makes some sense. The blade has been thinned down, and the edge appears very polished, but instead of stopping there a fine micro-bev has been put on with a lower-grit stone. Doesn't affect the appearance of the blade and thickness, but adds some longevity and gives some teeth.

JBroida
06-22-2013, 03:34 PM
i guess the only benefit is aesthetic... i was thinking in terms of performance. You could get the same results without going through all of that work.

zitangy
06-24-2013, 07:54 PM
Originally Posted by bamin
Never tried this, but what if you sharpen to a very polished edge and then put a micro-bevel on with a coarse stone? Would that have any kind of benefit or make a difference?

Originally Posted by JBroida
not really... its the same as sharpening on a coarse stone in general
Makes some sense. The blade has been thinned down, and the edge appears very polished, but instead of stopping there a fine micro-bev has been put on with a lower-grit stone. Doesn't affect the appearance of the blade and thickness, but adds some longevity and gives some teeth.


i guess the only benefit is aesthetic... i was thinking in terms of performance. You could get the same results without going through all of that work.

Hmnn... thinking aloud..

1) in between the striations wld be a finer/ striation (polished edge.) and the striation of the rougher stone will be first to go? Also if the higher striations just folds over the smaller striations will render the smaller striations useless in terms of bite function.


2) The final edge polish will be the last stone/ honing rod grit that touched the edge unless it is done at a lower angle with teh edge not touching the stone.


3) Jnats seems to be "unpure" with the diff materials giving diff grit size adn with its proclivity to be friable ( easily breaking down) we might as well "contaminate" our water stone by rubbing 2-3 water stone grits or just add a lump of assorted collected mud.

thus if contamination is good on Jnats, must also be good on synthetic water stone?

4) polishing with stone.. as Maxim mentioned.. the "texture" , watery or sticky or just the right amout of water wld make a difference and of course the pressure. My Naniwa stones gives a very light hazy "mist" not dark enough. I have not attained a respectable level at polishing at all. BUt can do a decent job with 600grit 3M sandpaper together with a blob of mud.

rgds
d

JBroida
06-24-2013, 10:12 PM
Originally Posted by bamin
Never tried this, but what if you sharpen to a very polished edge and then put a micro-bevel on with a coarse stone? Would that have any kind of benefit or make a difference?

Originally Posted by JBroida
not really... its the same as sharpening on a coarse stone in general
Makes some sense. The blade has been thinned down, and the edge appears very polished, but instead of stopping there a fine micro-bev has been put on with a lower-grit stone. Doesn't affect the appearance of the blade and thickness, but adds some longevity and gives some teeth.



Hmnn... thinking aloud..

1) in between the striations wld be a finer/ striation (polished edge.) and the striation of the rougher stone will be first to go? Also if the higher striations just folds over the smaller striations will render the smaller striations useless in terms of bite function.


2) The final edge polish will be the last stone/ honing rod grit that touched the edge unless it is done at a lower angle with teh edge not touching the stone.


3) Jnats seems to be "unpure" with the diff materials giving diff grit size adn with its proclivity to be friable ( easily breaking down) we might as well "contaminate" our water stone by rubbing 2-3 water stone grits or just add a lump of assorted collected mud.

thus if contamination is good on Jnats, must also be good on synthetic water stone?

4) polishing with stone.. as Maxim mentioned.. the "texture" , watery or sticky or just the right amout of water wld make a difference and of course the pressure. My Naniwa stones gives a very light hazy "mist" not dark enough. I have not attained a respectable level at polishing at all. BUt can do a decent job with 600grit 3M sandpaper together with a blob of mud.

rgds
d

quick notes...
1. this is at a point that doesnt really yield tangible results
2. yes
3. synthetic abrasives are not friable and will not act in the same way as a natural stone even with grit contamination... the results are interesting, but not the same as a natural stone.