Food Release: Stiction and the Grind

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Barmoley

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Sort of, it is usually selenium dioxide based compound. Selenium dioxide can be dissolved in water to form selenious acid.
 

Nemo

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Might actually be good in Oz...

Australian soil is notably deficeint in Selenium IIRC [emoji6]

Edit: Disclaimer: The author does not suggest that Australians consume Selenium based blueing or blacking solutions [emoji848]
 
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ecchef

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Martell did a nice blueing job on a Forgie conversion of mine. Hasn’t killed anyone yet.
 

Barmoley

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How well does it work against reactivity, is it more stable/durable than normal patina? In theory it should be.....
 

Pensacola Tiger

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How well does it work against reactivity, is it more stable/durable than normal patina? In theory it should be.....
My experience is that it is about the same as a well-developed patina.
 

merlijny2k

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I tried modifying the grind on a cheap santoku today to see if I could boost performance and test some idea's I had. Knife is a Rosenthal. Very soft chinese steel steel but decent spine thickness and balance and half decent grind to start from. Perfect for my purposes.

I tried to improve performance on food release and horizontal onion cuts. To achieve this I did three things:

I thinned the spine of the knife in the front half.

Ground the left side of the knife flat and very thin.

Put a small widebevel on the right side that stops where the granton edge begins. About 6mm from the edge.

Put a 70/30 assymmetric edge on it.

The results are as follows:

Horizontal onion cuts still suck. Seems like the grantons ruin the smoothness of the cut. Is this normal or am I doing something wrong?

Food release on onion parts is as terrible as can be.

Food release on potato is pretty darn good. Not as good as Kip's grind of course but better than I have seen on some cutting video's with J-knives said to have good grinds by knowledgeable people.

The complete disparity of onion vs potato performance leaves me puzzled. Any thoughts?
 

Jville

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I tried modifying the grind on a cheap santoku today to see if I could boost performance and test some idea's I had. Knife is a Rosenthal. Very soft chinese steel steel but decent spine thickness and balance and half decent grind to start from. Perfect for my purposes.

I tried to improve performance on food release and horizontal onion cuts. To achieve this I did three things:

I thinned the spine of the knife in the front half.

Ground the left side of the knife flat and very thin.

Put a small widebevel on the right side that stops where the granton edge begins. About 6mm from the edge.

Put a 70/30 assymmetric edge on it.

The results are as follows:

Horizontal onion cuts still suck. Seems like the grantons ruin the smoothness of the cut. Is this normal or am I doing something wrong?

Food release on onion parts is as terrible as can be.

Food release on potato is pretty darn good. Not as good as Kip's grind of course but better than I have seen on some cutting video's with J-knives said to have good grinds by knowledgeable people.

The complete disparity of onion vs potato performance leaves me puzzled. Any thoughts?
Perhaps, onions get caught up in the grantons.
 

refcast

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Kip, have you tried making a grind that:
-super thin behind the edge
-thick, lightly rounded shoulders like 2/3 spine thickness
-concave from edge to shoulder
-concave face
(so in total, like a gentle w)

I had a TF like that and it had crazy food release. But it accelerated through the cut. Didn't like that. But it didn't really wedge . . . until I softened the shoulders. Personally, I don't enjoy using the grind because I really like a linear feeling though the cut, but it is one of my top performing grinds I've experienced, as inconsistent as it was.
 

Kippington

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Kip, have you tried making a grind that:
-super thin behind the edge
-thick, lightly rounded shoulders like 2/3 spine thickness
-concave from edge to shoulder
-concave face
(so in total, like a gentle w)

I had a TF like that and it had crazy food release. But it accelerated through the cut. Didn't like that. But it didn't really wedge . . . until I softened the shoulders. Personally, I don't enjoy using the grind because I really like a linear feeling though the cut, but it is one of my top performing grinds I've experienced, as inconsistent as it was.
Sorry, I missed this post till just now. Could you please show me what you mean with a diagram? I don't quite follow from your description alone.
 

refcast

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tfgrind.PNG
I couldn't get the proportions quite right, but this is an over-exaggerated representation of my particular 270 TF denka wa-gyuto (don't have it anymore though). Just make the shoulders less fat, spine less fat, concavity a bit less extreme. I can't seem to do that with my skills on autodesk though.

The thing is though, that the grind changed in proportion a bit along the blade but that somehow allowed it to cut pretty much the same way. Perhaps because if it was consistent it might not have worked as well.

By crazy food release I mean, slices of potato fell off. Brunoise red bell peppers fell off after the cut, or rather, very little stuck on the upstroke of a push cut.
 

ecchef

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Busse used an interesting grind on some of their blades:
upload_2018-12-29_16-41-36.jpeg

Like a series of shallow Kippington hook grinds in parallel. I wonder how that would work on a gyuto?
 

refcast

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For my instance of knife, compared to takeda grind:

shorter blade height
thinner behind edge and concave, like kochi
slight concave blade face, less concave than takeda but with hammer indents

from what i've seen online, highest performance teruyasu fujiwara grind is like kochi, most workhorse/wedgey is just thicker behind edge.
 

HRC_64

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Concave oftentimes sucks IMHO because of the steering,
you want convex BTE because its more manuerable
and cuts better in product.

If you sharpen kitchen knife a razor blade or a scalpel
its "sharper" than a kitchen knife sure, but its too grabby
and it cuts food like dog-****...butchers also talk about
"knives being too sharp" ... its vary appernt in meat

I know this is all opinion (/personal preference) etc,
but I think its important to think thru...
ie, just what is "high performance" etc....
 

ecchef

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I think those butchers are probably referring to ‘toothyness’ rather than sharpness, or maybe a thin edge that deforms on contact with bone. I don’t really break down primals anymore, but for me there’s no such thing as a too sharp butcher knife.
 

Kippington

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I'm guessing 'too sharp' might have something to do with the knife cutting through things you don't want it to go through.
I sometimes find these two jobs to be annoying as hell with a super sharp knife, as it will simply cut through the thing I'm trying to separate...


But this is going a bit off topic. I don't think a concave grind has anything to do with this.
 

HRC_64

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But this is going a bit off topic. I don't think a concave grind has anything to do with this.
You've got the basic idea covered here.

If you look at a single beve, they use a clamshell (convex)
on the bevel, not a hollow for this exact reason.

The convexity in a single bevel isn't for food release,
because the slice is typically opposite the convexity.

The convexity is for "edge release" for lack of a better way to say it.
its not technially as sharp/acute...but its better handling when it cuts.

It "seems sharper" because its more controlled, and better handling
but its differnt property than edge refinement or bite.

(Simialrly the curve of the edge is there for the same reason,
but that's probably getting off topic).

Hope this is helpful explanation.
 
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HRC_64

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Note the bevel is not releasing the product, the slice is agains the ura (hollow side),
and the lack of surface area actually helps reduce sticktion.

>https://cdn-b.william-reed.com/var/...lleting-a-fish-with-a-Japanese-deba-knife.jpg

If you watch a fishmonger with a deba, similalry the bevel goes against the spine
(or the table side) when doing the filet cut (typically from right to left),
it isn't releasing off the bevel... because that side is sort of immovable.
 
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Kippington

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The convexity in a single bevel isn't for food release,
because the slice is typically opposite the convexity.
It's used both ways, slicing off both the left (0:10) and the right (1:10):
Also, it was the ura on the table side when he was skinning the fish, not the bevel... albeit a different usage from filleting off the spine.

But hey, I don't know enough to say a whole lot about single bevels. I'm very much a double bevel guy! :D
 

HRC_64

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Kip the 'typically' wasn't meant to imply every possible cut,
each knive has to be able to cut vertically as well.

The relation of convextiy to control is about steering, and assumes
you are making a cut that needs to be "steered"...
either because avoid or closely follow an object...
like a spine, the grain in flesh, the curve etc of the radish

A vertical cut, however being a straight cut, in theory
is no problem with a flat-side edge against product,
or a pure flat grind knive.
 
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panda

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I'm guessing 'too sharp' might have something to do with the knife cutting through things you don't want it to go through.
I sometimes find these two jobs to be annoying as hell with a super sharp knife, as it will simply cut through the thing I'm trying to separate...


But this is going a bit off topic. I don't think a concave grind has anything to do with this.
Yes!! Especially skinning fish, so many times I've cut right through the damn thing instead of it peeling..
 

Kippington

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Our fellow knife nuts over on zee German forums have asked me to make a hook grind knife for a passaround. They'd like to compare it against some of the major players in the area of food release:
(Dalman Knives and Xerxes)

This should be interesting... :D
I hear they are brutal in their criticisms, even going so far as to look at knives under a microscope to find faults...
(Kamon Custom)

I had two on order so I've gone and made them at the same time:





I still gotta make the handles.
The other makers would laugh if they found out how long it takes me to grind and polish one of these suckers. :oops: It takes me about 4 times longer than a standard grind... but at least I'm really happy with the consistency and how they're turning out.

I'm not gonna lie, I'm super interested in what these guys have to say! :D
 
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Kippington

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Well one of the Germans asked to go on my list a few months ago, and he's buying this knife for himself to own. The passaround will be organised through his end, and I highly doubt he would appreciate me sending his knife on a quick detour to someone else before he gets to hold it!

Sorry!
 
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