# Why kurouchi stainless-clad?



## Pirendeus (Jun 18, 2016)

If the main purpose of kurouchi is to create a barrier to protect the inner steel by retarding rust and limiting reactivity, why would a carbon knife also be stainless-clad? Wouldn't the stainless cladding by itself be sufficient protection? Why would a knife need both?


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## XooMG (Jun 18, 2016)

Pirendeus said:


> If the main purpose of kurouchi is to create a barrier to protect the inner steel by retarding rust and limiting reactivity, why would a carbon knife also be stainless-clad? Wouldn't the stainless cladding by itself be sufficient protection? Why would a knife need both?


Visual interest. Why assume a knife _needs_ it?


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## MAS4T0 (Jun 18, 2016)

Some people like the looks of KU and it allows for the surface to be left as is rather than polished (which would save labour and therefore $).


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## LifeByA1000Cuts (Jun 18, 2016)

Stainless in spite of kurouchi: You also preclude rusting tang problems that way... or rust undereating the finish... or coming down the spine... and you still get a stainless finish if somebody decides to abrade the kurouchi...

Kurouchi in spite of stainless: Aesthetics and purported? food release behaviour...


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## supersayan3 (Jun 18, 2016)

Carter has a video, where he explains his knife lines, and there he explains the differences between kurouchi and the stainless cladding. If I remember correct, he favours kurouchi as being better


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## chefcomesback (Jun 18, 2016)

supersayan3 said:


> Carter has a video, where he explains his knife lines, and there he explains the differences between kurouchi and the stainless cladding. If I remember correct, he favours kurouchi as being better



Yeah , he favours the white steel to have the best edge retention as well


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## MAS4T0 (Jun 18, 2016)

chefcomesback said:


> Yeah , he favours the white steel to have the best edge retention as well



:goodpost:


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## Pirendeus (Jun 18, 2016)

So, if kurouchi adds so much appeal, why aren't more knives made in this style? The majority of praised gyutos seem to be polished instead of rustic finish.


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## aboynamedsuita (Jun 18, 2016)

Pirendeus said:


> So, if kurouchi adds so much appeal, why aren't more knives made in this style? The majority of praised gyutos seem to be polished instead of rustic finish.



The appeal is to the individual user's taste. A lot of highly coveted knives such as Andy Billipp and Tsukasa Hinoura are KU finish


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## MAS4T0 (Jun 18, 2016)

Pirendeus said:


> So, if kurouchi adds so much appeal, why aren't more knives made in this style? The majority of praised gyutos seem to be polished instead of rustic finish.



It's personal preference, and what you expect are largely dictated by the price range.

I would agree that KU looks better than rough bare metal cladding, but if I'm buying a high end knife I expect it to be properly finished and not need KU to hide a rough finish.


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## lucabrasi (Jun 18, 2016)

There are tons of sought after ku knives. I'm not a fan myself, and it has prevented me from buying some knives. But there is no shortage of them. 

There are Shigefusa ku, Watanabe, Kurosaki, H Kato, Kochi, Heiji...could go on.


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## Sharpchef (Jun 18, 2016)

Blades like Takeda`s or JJ. Tritz from Germany, Brian Raquin France are forged to the desired shape and only the a part of the blade has to be grinded, so this shows a lot of blacksmithing skills!
Whole polished knifes could be stockremoval too! But this is no quality issue just for the look.

And in my opinion it looks cool! The KU or even polished hammering on the blade (i don`t think of the quite cheap Sakai Takayuki VG 10 Hammerfinish fake things.....)

Greets Sebastian.


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## daveb (Jun 18, 2016)

Some have turned KU into an art form. Yoshikane SLD comes to mind.


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## preizzo (Jun 18, 2016)

Good kurouchi finished knife doesn't get scratches on the side of the blade when you wash it. 
I like them a lot.


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## Pirendeus (Jun 18, 2016)

Everyone has suggested reasons why KU is good and useful (low price, easier production, more blade protection, some prefer the looks, etc.), and the only negative aspect mentioned is the subjective aesthetics. If all that is accurate, I don't understand why not all (or at least the vast majority) of knives are KU?


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## Matus (Jun 18, 2016)

Sharpchef said:


> Blades like Takeda`s or JJ. Tritz from Germany, Brian Raquin France are forged to the desired shape and only the a part of the blade has to be grinded, so this shows a lot of blacksmithing skills!
> Whole polished knifes could be stockremoval too! But this is no quality issue just for the look.
> 
> And in my opinion it looks cool! The KU or even polished hammering on the blade (i don`t think of the quite cheap Sakai Takayuki VG 10 Hammerfinish fake things.....)
> ...



+1


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## aboynamedsuita (Jun 18, 2016)

Pirendeus said:


> Everyone has suggested reasons why KU is good and useful (low price, easier production, more blade protection, some prefer the looks, etc.), and the only negative aspect mentioned is the subjective aesthetics. If all that is accurate, I don't understand why not all (or at least the vast majority) of knives are KU?



Perhaps subjective aesthetics?


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## kevpenbanc (Jun 18, 2016)

Pirendeus said:


> Everyone has suggested reasons why KU is good and useful (low price, easier production, more blade protection, some prefer the looks, etc.), and the only negative aspect mentioned is the subjective aesthetics. If all that is accurate, I don't understand why not all (or at least the vast majority) of knives are KU?



Stock removal blades don't have KU finish, plus some people like damascus finish.
Lots of different people want lots of different things


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## spoiledbroth (Jun 18, 2016)

my experience thus far is that carbon knives are cleaned (polished) daily, the reason for this, I am told, is that patina affects flavour (it is my presumption that this is a negative comment).

I think I recall somebody here saying that patina is considered dirty by sushimen in japan. Perhaps these ideas extend to KU finishes as well.


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## Ruso (Jun 18, 2016)

I'm not a chemist, but I always thought that patina prevents the further oxidation of the blade, which makes it less reactive and hence should affect flavours less not more.

Patina=dirt belive must be due to chef's wanting thier cooks to show that they care of their tools.


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## MAS4T0 (Jun 18, 2016)

I could be completely wrong here, but I always thought that KU was only generally used on 'home' knives and never on 'pro' knives.

I'd assume that most of the brands we're buying are focussed exclusively on the 'pro' market.

Have you ever seen a standard KU finish on yanagiba?


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## fimbulvetr (Jun 18, 2016)

A (relatively fresh) patina can indeed hold odors. I minced about 6lbs. of kimchi the other day, which turned the exposed carbon core of a stainless clad kochi jet black, which discoloration smelled to high heaven of cabbagey funk. I ended up polishing all that off that night, which made my wife ask if dinner included a particularly evil-smelling kimchi.

That said, my old Sabatiers, which I let patina wildly, never transferred off flavors to food. But I never prepared anything as fussy or "pure" as sashimi either. If I had a yanagiba, I'd likely polish it daily.


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## chinacats (Jun 18, 2016)

I totally get the ku, what I don't quite understand is the stainless part...:scratchhead:


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## aboynamedsuita (Jun 18, 2016)

MAS4T0 said:


> Have you ever seen a standard KU finish on yanagiba?



Why yes


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## MAS4T0 (Jun 18, 2016)

Wow! :dontknow:

I didn't expect that. Are they Watanabe?

Unrelated, but I just noticed the Canadian smiley while looking for that one. :yammer:



tjangula said:


> Why yes


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## aboynamedsuita (Jun 18, 2016)

MAS4T0 said:


> Wow! :dontknow:
> 
> I didn't expect that. Are they Watanabe?
> 
> Unrelated, but I just noticed the Canadian smiley while looking for that one. :yammer:



Yes they are Watanabe, I think ynot1985 also has a shig

Watanabe also has a small 150 lefty version for only ¥14,000JPY:




I am almost tempted at that price, but have a ton of wa and western rehandles to pay for shortly and some rehab work too, so gotta keep a lock on the wallet.

Btw I used to be a huge southpark fan back in the day, my parents didn't let me watch it when it first came out but I just watched at friends. Terrence and Phillip and Kraft dinner lol


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## Pirendeus (Jun 19, 2016)

supersayan3 said:


> Carter has a video, where he explains his knife lines, and there he explains the differences between kurouchi and the stainless cladding. If I remember correct, he favours kurouchi as being better


Is this the video to which you refer? At the 13:00 mark he discusses KU, but at the spot at which my link is cued, he's mentioning that he outsources his SS-clad lamination, and that SS-clad don't cut as well as non-SS clad, but he doesn't give an explanation, and his next statement is that SS-clad are his customers best performers. He also doesn't mention the possibility of SS KU (which is what Watanabe makes.) 
So, Carter gave some pertinent info, but still leaves me with more questions :-(


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## supersayan3 (Jun 19, 2016)

I can't see the video now, internet problems, but from your description this must be it.
True, he doesn't explain why KU cuts better than SS, and if all makers give their stainless cladding to some other factory.
But taken for granted that Carter knows traditional Japanese techniques, it must be more likely valid.


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## Pirendeus (Jun 19, 2016)

Ooops. I just re-watched the video and noticed I misinterpreted part of what Carter said. He DIDN'T say that stainless clad are his customer's best performers---he _actually_ said that stainless clad are "the best cutting knives that his customers have ever expeienced," and, in context, I think he meant that, specifically, his [Carter's] stainless clad are better than any other knives that customers have tried in the past.


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## aboynamedsuita (Jun 19, 2016)

I have two SS clad Carters, 160&275:





I spoke with Murray about the outsourcing some time ago and it is simply because you cannot effectively laminate the steel in-house. Apparently it has to be done in an oxygen free environment (probably vacuum?) and the distributors (presumably hitachi themselves) have the technology and capital to do this properly. Someone with an actual background in bladesmithing or metallurgy could probably comment better.

I don't the the cladding has as much to do with how well the knife performs as its not doing the cutting. However in one of my emails with Watanabe he did mention that honyaki has a smoother bevel as it obviously has no cladding and is generally mirror polished.


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## DanHumphrey (Jun 19, 2016)

Pirendeus said:


> So, if kurouchi adds so much appeal, why aren't more knives made in this style? The majority of praised gyutos seem to be polished instead of rustic finish.



Personally, I think it's wonderful that you can buy an arbitrary number of knives and have them all look different.


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## panda (Jun 19, 2016)

people love redundancy


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## osakajoe (Jun 19, 2016)

spoiledbroth said:


> my experience thus far is that carbon knives are cleaned (polished) daily, the reason for this, I am told, is that patina affects flavour (it is my presumption that this is a negative comment).
> 
> I think I recall somebody here saying that patina is considered dirty by sushimen in japan. Perhaps these ideas extend to KU finishes as well.



This is correct. Lots of Japanese chefs consider it unclean. They usually work in restaurants that have open kitchens and the customer can see the cutting food. You can now imagine why most Japanese kitchen knives are polished clean.


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## Matus (Jun 20, 2016)

osakajoe said:


> This is correct. Lots of Japanese chefs consider it unclean. They usually work in restaurants that have open kitchens and the customer can see the cutting food. You can now imagine why most Japanese kitchen knives are polished clean.



At a risk of sidetracking the thread - but isn't the patina-free knife worse for the food (affecting the taste) as a knife with stable patina? With a carbon clad knife that was re-finished I will get browning on onions - something that does not happen with a patinated blade. Also - if one puts a drop of onion juice on a clean iron cladding - it will start to turn brown (the juice faster than the blade) within few seconds. You can not wipe a knife that fast. This yields a question from me - would this be one of the advantages of a honyaki blade? The cutting steel is usually somewhat less reactive than the iron cladding, so no cladding means easier maintenance (in particular when polished).

Just thinking/wondering loud here ...


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## Pirendeus (Jun 20, 2016)

I just got a response from Watanabe-san:


> I shape Kurouchi petite for making polished petite. So polished version is thinner than Kurouchi.
> 
> Polished surface version is much smoother to cut than Kurouchi.
> You can cut more precisely.
> ...


So, it sounds like the kurouchi is just a normal step in his process to complete any blade. He clearly believes that a non-kurouchi knife is a superior performer to a finished blade...which is an interesting contrast to Carter's thoughts.


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## XooMG (Jun 20, 2016)

They're also talking about very different things when they are talking about cutting. Carter is referring to his edges, and Watanabe is referring to the blade faces.


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## Pirendeus (Jun 20, 2016)

Can you clarify, Xoomg? While they may be talking about different aspects of the blade, aren't they ultimately both talking about cutting performance?


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## XooMG (Jun 20, 2016)

Pirendeus said:


> Can you clarify, Xoomg? While they may be talking about different aspects of the blade, aren't they ultimately both talking about cutting performance?


I think there are too many assumptions being made about cutting performance. Grand castles of assumptions that a puny nerd like myself cannot hope to tear down.

I'll just reiterate. Watanabe is talking about the feel of the cut as the sides of the blade pass through an ingredient. Separation and friction. Carter is referring to the sharpness and stability of his edges with thin near-edge geometry. Neither is a complete story of cutting performance, but they both matter to varying degrees depending on what a person is cutting and how.


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## spoiledbroth (Jun 20, 2016)

Matus said:


> At a risk of sidetracking the thread - but isn't the patina-free knife worse for the food (affecting the taste) as a knife with stable patina? With a carbon clad knife that was re-finished I will get browning on onions - something that does not happen with a patinated blade. Also - if one puts a drop of onion juice on a clean iron cladding - it will start to turn brown (the juice faster than the blade) within few seconds. You can not wipe a knife that fast. This yields a question from me - would this be one of the advantages of a honyaki blade? The cutting steel is usually somewhat less reactive than the iron cladding, so no cladding means easier maintenance (in particular when polished).
> 
> Just thinking/wondering loud here ...


i had tbought there were some daily maintenance routines that can reduce reactivity on the face of a knife for short periods of time, though not totaly sure.

It could be this is all "an old wives tale" which is still held in japan, the restaurant industry in the west is full of inaccurate dogmatisms, one assumes the east is not dissimilar


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## MAS4T0 (Jun 20, 2016)

Matus said:


> At a risk of sidetracking the thread - but isn't the patina-free knife worse for the food (affecting the taste) as a knife with stable patina?



In my experience it depends.

The only iron clad knife I keep polished is a Mizuno.

If I do as Jon instructed and use a wet and a dry towel (to keep the blade clean and moist), I don't have any issues with reactivity or discoloration of food.


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## Pirendeus (Jun 21, 2016)

I just received some info from Murray Carter's shop:


> Prelaminated steel that is made in Japan (such as our stainless fukugo-zai) sits in a gas forge for a long time at the correct temperature. When we forge weld our own Kuro-uchi steel here it is only at that temperature for a matter of seconds, which maintains integrity of the grain structure, and thus, leads to a higher quality finished steel.
> 
> 
> So kuro-uchi knives are much more than just "unfinished." They are metallurgically superior to other steels that won't have such a refined grain structure due to their manufacturing techniques.


It sounds like the difference, then, might be more than cladding, which explains Carter's claims of kuro-uchi superiority. Does anyone know if all/most other craftsman have similar method of knife production (I.e. is all laminated stainless steel subject to the same issues)? If so, that would seemingly indicate that that most stainless knives have an inferior characteristic (subject to other factors, of course.)


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## JBroida (Jun 21, 2016)

not all laminated stainless steels are subject to the same issues... but knives from pre-clad stock would be


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## Pirendeus (Jun 21, 2016)

JBroida said:


> not all laminated stainless steels are subject to the same issues... but knives from pre-clad stock would be



Is one type more prevalent than the other? What about the oft-named brands---gesshin, mizuno, kono, hattori, Watanabe, etc?


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## Pirendeus (Jun 21, 2016)

And how important of an issue is this, relatively?


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## MAS4T0 (Jun 21, 2016)

JBroida said:


> not all laminated stainless steels are subject to the same issues... but knives from pre-clad stock would be



I'm sure I'm misunderstanding things here, but wouldn't the smith be able to 'fix' this with heat treatment?



Pirendeus said:


> Is one type more prevalent than the other? What about the oft-named brands---gesshin, mizuno, kono, hattori, Watanabe, etc?



With regards to Mizuno, they don't use stainless cladding.

You take your pick of iron cladding, honyaki or stainless mono-steel.


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## JBroida (Jun 21, 2016)

Pirendeus said:


> Is one type more prevalent than the other? What about the oft-named brands---gesshin, mizuno, kono, hattori, Watanabe, etc?



pre-clad stock is pretty common... even within the brands you mentioned, it can vary. All of them use both types, so it will depend on the specific series. Entirely hand forged and laminated in house options are becoming more and more rare as time goes on, but they still exist for sure.


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## JBroida (Jun 21, 2016)

MAS4T0 said:


> I'm sure I'm misunderstanding things here, but wouldn't the smith be able to 'fix' this with heat treatment?
> I wasnt making a comment on the HT, as there are people out there who know way more about this than i do... i was just commenting on the fact that carter says this is an issue of prelaminated stock (sheets and bars), and so lamination that is done in house (including stainless lamination, which, while a huge pan in the ass, is possible to do) would not be in the same group as what he was talking about


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## Matus (Jun 21, 2016)

Jon, with the little I have read about the HT I suppose the makers can and do adjust their HT procedure. If steel sits at high temperatures for unnecessarily long the grain size will grow what will have large impact on the toughness at given HRC and the steel would probably chip easily. Since that is rather rare among the knives mentioned I am blindly confident that those makers know what they are doing.

And, not to forget, is there actually a reason to assume that ALL (or MOST) of the pre-clad steel is exposed to prolonged exposure at high temperatures? I mean - we may be discussing a non-existing problem (which of course does not make it any less important and thus worthwhile the discussion  )


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## MAS4T0 (Jun 21, 2016)

JBroida said:


> I wasnt making a comment on the HT, as there are people out there who know way more about this than i do... i was just commenting on the fact that carter says this is an issue of prelaminated stock (sheets and bars), and so lamination that is done in house (including stainless lamination, which, while a huge pan in the ass, is possible to do) would not be in the same group as what he was talking about



I wasn't meaning HT in terms of 'normal' HT, but was thinking that you could refine the grain size through thermal cycling.


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## Ruso (Jun 21, 2016)

Sorry, what is pre-clad stock? i.e. _"...but* knives from pre-clad stock* would be "_


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## MAS4T0 (Jun 22, 2016)

Ruso said:


> Sorry, what is pre-clad stock? i.e. _"...but* knives from pre-clad stock* would be "_



It's a sheet of factory produced san-mai sheet metal.

Knives can be cut and ground from it with no forging needed, almost as if it were mono-steel.


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## Ruso (Jun 22, 2016)

So, it's like stock removal but on san-mai knife? I thought such thing didn't exists. Damn, all is a lie, all those videos of Japanese old folks hammering down the hot steel is a lie!?!?!! NOOOO!O!O!OO!OOO


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## Pensacola Tiger (Jun 22, 2016)

Ruso said:


> So, it's like stock removal but on san-mai knife? I thought such thing didn't exists. Damn, all is a lie, all those videos of Japanese old folks hammering down the hot steel is a lie!?!?!! NOOOO!O!O!OO!OOO



The operative word is "can". Carter, for one, starts with relatively thick pre-clad stock and forges it thinner before grinding. Takeda does the same. I'm certain other smiths do as well. Do you consider those knives "stock removal"?


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## MAS4T0 (Jun 22, 2016)

Ruso said:


> So, it's like stock removal but on san-mai knife? I thought such thing didn't exists. Damn, all is a lie, all those videos of Japanese old folks hammering down the hot steel is a lie!?!?!! NOOOO!O!O!OO!OOO



If you see a perfectly straight lamination line, it's most likely been made by stock removal of mass produced san-mai material.

Just because it's not been forge welded by the blade-smith, it doesn't mean that it's not undergone forging; a lot of smiths will forge in the bevels or forge in the taper of the blade and this shows up as a more animated lamination line.

This photo of a Hiromoto AS gyuto and matching petty shows this very well. The petty is from thinner stock and seems to be entirely stock removal, but the thicker gyuto has some randomness to the lamination line which would imply that the material has been forged by the knife-maker.


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## Ruso (Jun 22, 2016)

I see. Thank you for the explanation.
Based on the comments above, it looks like if the knife is SS clad it was most likely made from pre-clad stock; is it correct?


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## JBroida (Jun 22, 2016)

for what its worth, there are a number of makers using preclad stock that dont have straight lamination lines... a lot of people still forge pre-clad stock a bit too


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## Keith Sinclair (Jun 22, 2016)

Does anyone know the process of making the animated lamination line? When it patina's looks like the Hamon line on a katana always wondered how they do this.


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## MAS4T0 (Jun 22, 2016)

JBroida said:


> for what its worth, there are a number of makers using preclad stock that dont have straight lamination lines... a lot of people still forge pre-clad stock a bit too



That's what I was trying to express.

Both of those Hiros are most likely made from pre-made san-mai, but the petty appears to be entirely stock removal while the gyuto seems to have been forged somewhat.

Would you agree?




keithsaltydog said:


> Does anyone know the process of making the animated lamination line? When it patina's looks like the Hamon line on a katana always wondered how they do this.



It's just randomness which comes from deforming the layers through forging.

Unless there were grind issues, uniform pre-made san-mai would give a straight line, but almost any kind of forging operation will result in a more animated lamination line as core steel and cladding are no longer completely even, straight and uniform in thickness along the length of the blade. Through forging the smith would cause the core steel to have some waviness (when viewed from the spine), which would give an uneven and random pattern when the blade is ground. Basically, it's caused by forging.


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## JBroida (Jun 22, 2016)

MAS4T0 said:


> That's what I was trying to express.
> 
> Both of those Hiros are most likely made from pre-made san-mai, but the petty appears to be entirely stock removal while the gyuto seems to have been forged somewhat.
> 
> ...



yeah... makes sense


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