Creating utsuri

[C0D]

  On 4/3/2025 at 12:39 PM, Rayhan said:

So, back to this. 

 

@Rivkinthermocycling yes. Please stop putting the cart before the horse. We do not need to speak of Yaki-ire at all when we speak of Utsuri. 

 

The development of a blade has its stages and if the smith uses thermocycling (annealing is a process that is involved also but not mutually exclusive) 

 

https://knifesteelnerds.com/2021/08/28/how-to-thermal-cycle-knife-steel/

 

I know knife steel nerds is not a scientific journal but this article helps. 

 

If we imagine the process where we are changing the structure of the steel as we go along all the way till Yaki-ire then we can build the visual base for utsuri. @C0Di am not fortunate enough to see Utsuri being produced in real life today, being produced infront of my eyes to say, however, if you have this information please share it here so we can all benefit. I can say that i have an Ichimonji blade and Aoe that both have wonderful Utsuri and will share that when i am close to them again after my travels. 

 

 

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I don't see any mention to utsuri or hamon in the article, I don't know how can be relative to the utsuri topic.

This process shows how grain size changes during cycles of normalizing and annealing. The grain size doesn't affect the appearance on the ji, it might influence the hamon in some degree, but depends on how the yakiire is performed 

[Apercus]

I believe there are several effects that are called utsuri. The description given by Yoshindo Yoshihara I believe is describing the formation of banite in the microstructure. Banite forms at a different temperature range than martensite. It is almost as hard as martensite but is much tougher and resistant to cracking. It is very desirable from the viewpoint of structural integrity. I believe many older blades were made without the use of clay. I suspect a large bar of iron was heated to a suitable temperature and the edge of the blade to be heat treated was placed against it to allow heat by conduction. I don’t see any other simple way to achieve a controlled differential application of heat on a long slender sword without modern technology. I have experimented with this and have produced “utsuri” similar to what I see on older blades. Not every steel will produce utsuri. As Rivkin mentioned, different steels have different thermal conductivity characteristics. It is difficult to produce utsuri on most modern steels, especially with high carbon content or alloying elements. I find that tamahagane with a medium carbon content works better for producing utsuri. 
I did X-ray diffraction analysis on a mid kamakura tachi with vibrant utsuri and found the core steel was high carbon (.7%) while the exterior layers were mid range carbon content (.45 % to .55%). 
I haven’t done an exhaustive study of the effects called utsuri. I don’t have the samples, time, money, energy, etc. These are just my limited observations from several years ago, so take that into account.

[Rayhan]

  On 4/3/2025 at 12:53 PM, C0D said:

I don't see any mention to utsuri or hamon in the article, I don't know how can be relative to the utsuri topic.

This process shows how grain size changes during cycles of normalizing and annealing. The grain size doesn't affect the appearance on the ji, it might influence the hamon in some degree, but depends on how the yakiire is performed 

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Im getting on my flight. Gents and ladies please think how these process(s) relate tonthe creation of a blade over weeks and months and not from hours or minutes. Sayonara. 

 

Ps: for those in Japan now the NBTHK is showing Kiyomaro (excellent examples and not so excellent but all Juyo) it is good to see what experts mean when they say excellent Kiyomaro and not so excellent. Masahide and Naotane also. 

 

The Tokyo National Museum is showing Soshu and Bizen (also Bitchu) in all it's glory, go see. 

 

Not to mention the other sword specific museums in Nagoya and such. 

 

 

[Apercus]

As a side note, Howard Clark produces Japanese styled blades in a process that maximizes banite formation instead of martensite. The process allows for an edge almost as hard but greater toughness and resistance to breaking overall.

[Rayhan]

  On 4/3/2025 at 1:09 PM, Apercus said:

I believe there are several effects that are called utsuri. The description given by Yoshindo Yoshihara I believe is describing the formation of banite in the microstructure. Banite forms at a different temperature range than martensite. It is almost as hard as martensite but is much tougher and resistant to cracking. It is very desirable from the viewpoint of structural integrity. I believe many older blades were made without the use of clay. I suspect a large bar of iron was heated to a suitable temperature and the edge of the blade to be heat treated was placed against it to allow heat by conduction. I don’t see any other simple way to achieve a controlled differential application of heat on a long slender sword without modern technology. I have experimented with this and have produced “utsuri” similar to what I see on older blades. Not every steel will produce utsuri. As Rivkin mentioned, different steels have different thermal conductivity characteristics. It is difficult to produce utsuri on most modern steels, especially with high carbon content or alloying elements. I find that tamahagane with a medium carbon content works better for producing utsuri. 
I did X-ray diffraction analysis on a mid kamakura tachi with vibrant utsuri and found the core steel was high carbon (.7%) while the exterior layers were mid range carbon content (.45 % to .55%). 
I haven’t done an exhaustive study of the effects called utsuri. I don’t have the samples, time, money, energy, etc. These are just my limited observations from several years ago, so take that into account.

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Modern steel does not require the process that producess Utsuri as stated in my previous post.

[Brian]

As a major knife guy, collector and dealer, I can tell you that thermocycling is used a lot in custom knifemaking nowadays. It is used on high end knives.
Now that may be unrelated to the topic at hand, and is unrelated to utsuri production, but saying it is not widely used or not economical is not true at all. It's used by numerous factories and custom makers seeking the best possible performance out of steel.
Also, carbon content is definitely closely linked to utsuri...all the articles you read mention differing carbon content in various schools and smiths, and I think it's obvious that both temperature and carbon content are vital in the production of utsuri.

Edit to add: Actually, I think the knifemaking process may relate quite a bit when it comes to Nihonto, considering they are both dealing with the crystalizing formations and normalizing to increase strength and durability
https://knifesteelnerds.com/2021/08/28/how-to-thermal-cycle-knife-steel/

[C0D]

Carbon content is related to utsuri no doubt of that, a 0.45% C can't produce utsuri, while over 0.7% can.

Anyway I shared enough of my personal experience and Japanese swordsmiths experience, the readers can decide what they think works better. The topic is already exhaust for me

[Apercus]

The only way to determine answers on this subject is through trial and error error controlled experimentation. Results provide bits of information. A lot of trials and results eventually define the science. Everything else is speculation and should be treated as such.

[Apercus]

I have a juyo Ichimonji tachi with vibrant utsuri appearing in an area that has .45% carbon content. I tend to think your conclusion that .45% carbon content steel can’t produce utsuri is incorrect

[Rivkin]

  On 4/3/2025 at 1:22 PM, Brian said:

As a major knife guy, collector and dealer, I can tell you that thermocycling is used a lot in custom knifemaking nowadays. It is used on high end knives.

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Sorry - I am not a title's guy, so I am still not convinced it involves multiple, beyond maybe two, quenchings.
Otherwise its a matter of what's defined as thermocycling. Can easily imagine I am operating on a different terminology than knifemaking. 

[Franco]

  On 4/3/2025 at 7:28 AM, Matsunoki said:

So what actually is this utsuri like effect? In what way is it not the same? Method of production (there seems to be several), metallurgical structure? Be good to know what looks like utsuri but isn’t.
@COD has the benefit of having the blade in hand vs working from images….plus he saw the smith at work.

In what way is koto utsuri higher quality? Does it improve flexion tolerance? Does it improve cutting? Does it improve longevity.

Observing this interesting topic (as a real novice)  it seems we have very few hard facts but a great many opinions.

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If you haven't read Yamanaka on the subject of utsuri vs utsuri like effect then you're missing something. And if you have read it, read it again. Although Yamanaka has a section on utsuri, you'll find other tidbits scattered about. Some of the information will only become clear when and after you actually see an example of what he's talking about.   So that's what he meant!

 

I've already mentioned the words intentional and incidental. In my experience utsuri can be both. Intentional utsuri becomes obvious. It has a definite pattern. It has uniformity. There's no mistaking it when you see it. Incidental utsuri will be more like an afterthought, it will have a randomness to it.

 

An utsuri like effect will be dull and lifeless in comparison to real utsuri. The nioi and nie (if it can even be called that) will not be defined. It will lack reflectiveness, brightness, whiteness.

 

Bizen nioi utsuri will be like looking at a surface covered in diamond dust. Rai and Soshu nie utsuri will appear like individual specs of diamonds clustered together. These descriptions are my own. On top quality A+ utsuri works, the steel begins to have that wet look that is only seen on top quality swords.

 

Form follows function. Form follows function. Form follows function. One advantage of early swords were that swordsmiths had direct feedback. The teacher student relationship was chained and unbroken by disruption. 

[Brano]

First of all, I think that swordsmiths in the Early Koto period did not create utsuri intentionally.
They primarily made weapons.
The utsuri was just a side effect of the material's sensitivity to the yakiire process
There are many great Kamakura blades from the Bizen school that do not have utsuri
I'm not even sure if they were able to get the blade surface to a state where they could see the utsuri.

 

Nice to see you back here @Rayhan

[Tohagi]

Another point was... there was no artificial light to "observe" utsuri. Most token teachers had to wait for proper light (dawn? ) once a day.

Still utsuri seems to have been à well mastered process in Bizen...

[CSM101]

I once wrote an article about Jigane & Jihada with photo of different kinds of utsuri. Here is a Ko Bizen Muneyoshi with jifu utsuri for a better understanding.

[Lewis B]

A timely reminder to all those, like me, who like a blade exhibiting utsuri. Nefarious sellers out there praying on the appeal of this feature.

 

https://www.facebook.com/photo/?fbid=2401552303244992&set=pcb.2401556073244615

 

https://www.facebook.com/photo/?fbid=2401552296578326&set=pcb.2401556073244615

 

A warning from Andrew Ickeringill

"

A warning to sword collectors...

Please have a look at these pics taken from a Japanese auction site, when you look at this utsuri, what do you see? Have a good look and think about it before reading the below...

This kind of utsuri was drawn to my attention a few years ago, a client had asked me to open a window on an old tachi. As soon as I saw the blade, I knew something was off... it had been acid etched (not unusual) but something else was going on with the utsuri.

After a few minutes pondering I concluded that the utsuri was fake, but the owner wasn't convinced and still wanted a window opened. Sure enough, the window revealed the utsuri was completely artificial, it came right off and didn't return.

I believe the sword pictured here has had the same treatment, it has no utsuri... well it might have some kind of utsuri underneath the artificial one, but I doubt it.

I'm guessing it's been created using some kind of VERY strong chemical process, applied either very carefully with a cotton bud stick, or perhaps a stencil was used as a guide.

I've been seeing this kind of "utsuri" quite a bit recently, mainly coming from the Japanese auction sites. It's a very cheeky deception that I imagine has fooled many people.

So, how can I tell this is fake just from looking at pics? That's the hard part to explain, I'll do my best...

For starters, how do you view utsuri? Similar to the way you view the hamon. Real utsuri generally can't be seen very well from the angle that you'd normally view the jigane from, which is from directly above. But the "utsuri" in these pics shows up very strong in the jigane pics.

What about the shape/pattern of this "utsuri"? It seems there's a contrived shape and repetitive pattern. On a sword with this kind of gunome-ba, I'd expect real utsuri to mirror the hamon in a similar flow, the utsuri would rise where the hamon dips into valleys, and the utsuri would fall where the hamon peaks (this isn't always the case with real utusri, for example shirake-utsuri). But with this sword you can clearly see the pattern of the utsuri is often at odds with the flow of the hamon in a very unnatural way.

Also, please note the granule-like/mottled texture of this "utsuri", it's a result of the acid and you don't see that effect in real utsuri.

One more thing, look how defined this "utsuri" is, especially the area down towards the hamachi where they've tried to emulate a mizukage-like effect. It's so sharp and defined, like it's been painted on, well it basically has been!

So, just beware of these Japanese auction sites and their swords, some are gimei, some are acid etched in the hamon and jigane, and some have completely artificial utsuri. I'm not saying don't buy from these sites, there are some good swords to be found there, but you need to be aware it's like navigating a minefield, please be cautious and don't get had! I wouldn't recommend buying anything from these sites unless it's at least papered Hozon level."

[ROKUJURO]

  On 4/3/2025 at 11:56 AM, C0D said:

.....Of course any form of hardening is a thermocycling, because it changes the composition of the metal through heating and rapid cooling....

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Manuel,

while I agree with much of what you say, I would remind you that short-term heating-up a blade will not change the composition of the steel but only the molecular structure at best. Considerable carbon migration - which could result in a change of composition -  takes place after long heating cycles or exposing the work-piece to very high temperature.

I am on your side when you are asking for evidence - written in old papers or explored by modern research methods - about the making of UTSURI in KOTO times. Where is the information coming from? I would not consider "logic" as proof.

[Rivkin]

Discussions about utsuri tend to follow the same pattern - there are few postulates and there are groups of people defending each.

The basic problems are:

 

a. There is no per se scientific analysis of utsuri which clearly demonstrates what it is. Unfortunately I am not aware of someone taking an old Bizen blade, looking at the structure and saying - within utsuri we have (a), outside we have (b). In blades without utsuri we have only (b). Repeat to confirm.

Instead there are many people making conjectures about what (a) should be. Basically like wootz studies used to be around 1990-2000: there were couple of blades analyzed, but 95% of information in publications were conjectures which went like "since wootz got to be superior because otherwise why would they do it, it is probably nano-fulleren-carbon etc.". Reality is most old ironworking is about trying to adapt to very severe material/temperature/timeframe constraints. The lost knowledge of quantum-coherent-supersteel is associated with professors submitting a paper to nature.

. 

b. Related to previous point - no clear experiment analyzing what is jifu utsuri, midare utsuri, Muromachi bo utsuri etc.. Is it the same (a)? Different? Is hardening or composition what determines jifu/midare/bo structure?

 

c. Modern methods of making utsuri have one purpose - to make utsuri. Hopefully looking like the old one. The simplest way to do it is a fine done acid etch, but its cheating and yes, its mostly visible from the top. Still its popular in Japan. Real deal usually needs to be looked at from a side. But again - not always. So does it mean if I manage to make utsuri today I know how ko Bizen did jifu utsuri? Open question. Plus people who made really good utsuri in the past 200 years tended to be a bit silent about the details.

 

So to summarize - in wootz only when people did the analysis of 30+ blades it became apparent what the "real wootz" is (except there are many still arguing that it is not). Studying utsuri basically means sacrificing (non-destructive testing is not used in professional iron metallurgy) a few old blades, targeting utsuri versus non-utsuri areas.

I did such study with a single  Muromachi Uda blade and basically it was very dirty steel with visible composition variation which even without hardening would produce some "utsuri" during polish. Is this universal? No, I don't think so. But I do suspect that considerable portion of utsuri variery is because of composition variation multiplied by hardening effect.

[Jacques]

  Quote

 because it changes the composition of the metal through heating and rapid cooling....

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Wrong. It doesn't change the composition of the metal, which is iron + carbon, but it does change the arrangement of the atoms, which take on different shapes.

 

 

[reinhard]

Do not forget:
It's the polishing technique that makes utsuri visible, or not.
For a long time people believed, utsuri was an old, lost quality, forgotten during Edo-times.
They were proven wrong by increased polishing techniques.

What makes the difference now:
Kind and quality of the utsuri!

reinhard

[Robert S]

As an example of Utsuri and the complexities of creating them, here's an example of utsuri from a wakizashi - but this small area of utsuri is the only place it is found on this nihonto,  so it appears that the specific conditions required to create utsuri only occurred on one small area on the blade - possibly accidentally?

[Rayhan]

So we have some very nice images being shared and this is the main way we can study online, with shared images or video. There are other members being silent but who have access to great data to help this query.

 

Perhaps if the more knowledgeable that have access to data could summarise which swords in the juyo and tokuju registry have been noted to show Utsuri and in what form we could break this up into era, utsuri type, frequency, etc. Much to be learned from the study of zufu and its contents as well as  how they (the NBTHK) phrase the presence of utsuri on a sword. 

 

From my perspective the presence of utsuri denotes excellent and consistent heat treatment of steel and the uniformity in that particular area of the steel. Because it is a sign of excellent thermocycling and consistent practices that leads to uniform steel fit for purpose. Especially when dealing with raw materials such as forge made or tatara made Tamahagane. This raw material, although beautiful to behold, is not a forgiving medium and comes with it's own challenges when striving for "good sword steel ".

[Rayhan]

Oh my, so much time has passed and no input from the more knowledgeable. 

 

Perhaps it is my oni spirit causing commotion...

 

Anyway, utsuri in general falls to the Bizen tradition and the Yamashiro. Both schools show very distinguished traces of utsuri.  We know that Bizen and Yamashiro forged in heats that were low in the context of Nihonto. We know that the sword smiths in the Heian/ Kamakura produced their own raw material and indeed followed the river systems in Bitchu, Bizen etc to produce tamahagane. Later this moved further north and spread across Japan. And so Utsuri might be a sign of lower quality steel being refined to a huge milestone. 

 

Interesting is it not, that these two schools came together to make soshu. Forging at such high heats that impure remnants are left behind. 

 

Also an interesting note is that by the time soshu came round we had tatara making much higher grades of raw material. 

 

Perhaps @Brano @Jussi Ekholm @Gakusee you might have some data? Sorry to call you out.

[Brano]

I have never statistically evaluated the presence of utsuri for higher rated blades in a time and school
I agree with you that the prerequisite for the emergence of utsuri is first-class tamahagane. We can only assume that the typical appearance of Jifu utsuri is a consequence of fluctuations in the homogeneity of the raw material with respect to carbon content
I am not a metallurgist and am not competent to make any conclusion
However, I can attach examples of three different blades. All have nioiguchi in the ko-nie.
The first is the Soden-Bizen school from the Nanbokucho period
Prominent midare utsuri

[Brano]

The second is a blade from the Rai school also from the Nanbokucho period. Setsumei describes utsuri as jifu utsuri but I would rather call it nie

-utsuri

[Brano]

The third is a blade from the end of Kamakura, Bitchu/Bingo area
Setsumei describes it as shirake utsuri
Although the utsuri on this blade is not that pronounced, it is very sensitive to changes in the angle of light and the reflection looks like a hologram
It is my favorite blade by the way

[Jussi Ekholm]

Nice to see you again Rayhan.

 

Unfortunately I am pretty much clueless when it comes to these finer details in sword appreciation. I just like the huge swords that can be appreciated even from far away.

 

I would think like Reinhard that perhaps polishers (or swordsmiths) could offer best insight on this subject. At what stage the utsuri becomes visible in steel?

[Jacques]

School with utsuri 

 

NIE UTSURI
Awataguchi
Rai
Taima
Hôjôji

SHIRAKE UTSURI
Kanabo
Sengo (faible)
Shiga (Yamada Seki)
Akasaka Senjuin
Zenjo
Seki Kanemoto
Seki Kanesada
Hachiya
Kanefusa
Kanetsune
Gassan
Fujishima
Uda
Motoshige
Omiya (weak)
Kongobei
Miike
Yukihira
Takada
Naminohira

JIFU UTSURI
Ohara
Ukai

MIDARE et CHOJI UTSURI
Ko Bizen
Ichimonji
Osafune
Yoshii
Hatakeda
Wake no Sho, Nitta no Shô

BO UTSURI
Osafune
Aoe, en Nanbokuchô (with some midare elements).
Yasuyoshi (Sa)
Mihara

DAN UTSURI
Niô

[Gakusee]

  23 hours ago, Rayhan said:

Oh my, so much time has passed and no input from the more knowledgeable. 

 

Perhaps it is my oni spirit causing commotion...

 

Anyway, utsuri in general falls to the Bizen tradition and the Yamashiro. Both schools show very distinguished traces of utsuri.  We know that Bizen and Yamashiro forged in heats that were low in the context of Nihonto. We know that the sword smiths in the Heian/ Kamakura produced their own raw material and indeed followed the river systems in Bitchu, Bizen etc to produce tamahagane. Later this moved further north and spread across Japan. And so Utsuri might be a sign of lower quality steel being refined to a huge milestone. 

 

Interesting is it not, that these two schools came together to make soshu. Forging at such high heats that impure remnants are left behind. 

 

Also an interesting note is that by the time soshu came round we had tatara making much higher grades of raw material. 

 

Perhaps @Brano @Jussi Ekholm @Gakusee you might have some data? Sorry to call you out.

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Ray, thanks for chiming in and good you called us out as nowadays I don’t have much time for here. 
I have to disagree with you about Utsuri being on lower quality steel. Utsuri was produced, according to some scholarship, by Bizen den smiths to compensate for the softer blade forged at lower temperature. Utsuri rehardened the body of a Bizento which was not as hard as the nie-rich blades forged at higher temperature. Utsuri is evident on good / high- quality steel and blades. 

To move away from the above thesis, utsuri was produced by other schools which hardened in nie (eg Yamashiro / Rai and later Bizen such as Soden or sub schools such as Aoi and Unryu) but as Brano says, there it is mostly referred to as nie utsuri. Jacques has produced a very good list above. I will summarise it as follows: generally early utsuri (KoBizen) tend to jifu and choji/ midare, Yamashiro one tends to be nie and less ostensible than the Bizen utsuri, and later utsuri (Nanbokucho / Muromachi) tends to appear as bo or shirake across various schools. Various sub differences across the latter. 
 

Brano: by the way jifu utsuri is not about nie vs nioi even though it is more often evident in nie-rich blades such as KoBizen (KoBizen tended to forge at higher temperatures and render the nioiguchi more in nie / konie). It is about the shape as in fingerprint blobs on the blade. 

[Gakusee]

Midare utsuri on a Hatakeda sword 

[Gakusee]

Jifu on a Tomonari