Looking for information about Yakite-kusarakashi

[FlorianB]

I haven’t found a detailed description of yakite-kusarakashi yet.

Even Markus Sesko’s book gives only a vague account.

This technique was used by some schools like Hoan.

 

Knowing it is an European invention and together with my own experience with etchings (artistic prints) I guess the vital process as follows:

 

The surface of the plain Tsuba is covered with lacquer to prevent a corrosion by acid. 

• Either the motif is painted on a Tsuba or 
• the piece is completely covered with lacquer and the motif is scratched in (for example an amida yasurime).

Then it is put into an acid bath (I suppose it was hanged into a small canister containing the etchant) and the acid affects all uncovered areas of the metal.

Note that the corrosion deepens uniformly irrespective of the width of the openings.

After a certain time the Tsuba is taken out of the etchant, remnants of acid are washed off and the cavities form now a relief with sharp ridges.

Thus at least the yakite process will smooth the surface and incidentally the lacquer is removed by burning (or does it flake off?).
This seems logic because recently I read on this board that urushi can’t be dissolved with chemicals.

 

 

There are also pieces on which acid has been dropped randomly directly onto the surface to get a more weathered look (i.e. more sabi).

 

I hope I understood the procedure correctly but I don’t know neither which acid was used (I used sulphuric acid) nor the time which is necessary to corrode an iron Tsuba in this way (I only etched plates of soft metals like copper and zinc).

 

Maybe someone has more detailed information?

Thank You in advance!

[Geraint]

Dear Florian.

 

Just some thoughts to add.  Like you I have etched soft metals but this link, https://needlewatcher.com/marketplace/wp-content/uploads/2020/09/CN_Sugaie-Dragon-tsuba.pdf  suggests the aqua forte or nitric acid approach for iron.   It is perhaps the case that a generalised use of the term lacquer here might be less than helpful.  The term I am used to is stopping out varnish and this is a much softer medium than Japanese lacquer and can be removed with a solvent thus avoiding the use of heat.   I attach images of a tsuba I own which shows an etched design, there is something quite distinctive about the outline of the etched areas which would suggest that this one has been etched but then not subject to yakite which would give a much more nuanced surface and design outline I feel.

 

 

 

 

All the best.

[Steve Waszak]

Hi Florian,

 

Interesting topic.  My understanding with Hoan tsuba is that he would "paint" on the motif with urushi, and then place the guard in an acid bath so that the surface of the piece around the urushi-covered areas would be affected, leaving the motif raised above the surrounding plate surface.  The term often used for his tsuba is "yakite kusarashi," which implies that there is also an application of heat in some manner.  However, some argue that attempting to apply heat to the surface of a tsuba to achieve "melty" effects doesn't really work, and that the surfaces that present with melted-looking areas are achieved via the acid treatments, only.  I do wonder how much there is in the old ways of metal working in Japan that we do not know about or have access to.  

 

[ROKUJURO]

Florian,

 

as far as I know, the above described technique has nothing to do with YAKITE KUSARASHI (or KUSARAKASHI) but it is the way to create TSUBA with a shallow design as in KAMAKURA BORI or HOAN style. Removing URUSHI after the etching is no problem as it is an organic substance. Not much heat is necessary to get rid of it.

I once discussed YAKITE SHITATE and YAKITE KUSARASHI with Ford, and we shared the opinion that all information available on these techniques lacked metallurgical knowledge and were written/posted as assumptions only.

But it is safe to say that YAKITE KUSARASHI is a chemical treatment of iron TSUBA using heat and acidic substances at the same time to speed up artificial corrosion on the surface. Depending on the nature of the used iron, different surface structures can be achieved.

It is important to note that these processes do not necessarily need pure or concentrated acids as we know them in the West. If time was not important, natural sources of acids work as well. We know this from other cultures where etching has been a standard technique on weapons for hundreds of years.

 

[FlorianB]

Obviously I poked my nose into a topic which seems far more complicated I thought. 
At least the only way to explain undocumented techniques is by deduction and assumption.

 

Concerning removing of lacquer the information I read was obviously wrong.

However, I was thinking also about a mechanical removal by scraping or burnishing.

Geraint,

That is exactly what an etched Tsuba would look like without further treatment. 

Steve 
I have some other Tsuba with a smooth surface (and tekkotsu) which I always understood as a result of yakite according to the doctrine.  
Creating a high relief like this on Geraint’s Tsuba above is one method, but for an amida yasurime it is far more easy to scratch lines into a lacquered cover.

 

Jean
My problem was how to connect the terms „etching“ and „heat“, so my idea seems logic to me.

 

8 hours ago, ROKUJURO said:

If time was not important,

– let them rust! 

 

 

[ROKUJURO]

2 hours ago, FlorianB said:

..... I was thinking also about a mechanical removal by scraping or burnishing. 

Mechanical removal is possible, but it will probably not create a "natural" looking surface. Scraping and grinding would work best on a completely level surface. 'Burnishing' (= MIGAKI JI) is a technique which does not remove material. It only creates a glossy surface.

URUSHI will stick firmly to a clean metallic object and is quite difficult to get rid of with mechanical methods as it creeps into the smallest gaps and fissures.

Please find below a test-piece with (artificial) corrosion on one side and URUSHI on the other. Without heat, it is not possible to remove the lacquer completely as it remains in the fine structures of the surface. However, I scraped and ground most of it away, leaving an almost glossy surface.  

[Robert S]

Just a detail, but it's also worth nothing that in most cases acid etching doesn't result in a vertical sides groove or area, like you show in your illustration.  Generally, the exception to that rule is dutch mordant on copper, but that's a whole other story.  You're also unlikely to get a smooth surface left where etched, due to differences in metal composition, acid movement, etc.  The surface shown on the tsuba illustrated is pretty typical.

 

Robert

[Steve Waszak]

Here is Shodai Hoan tsuba with a yakite-kusarashi (or kusarakashi -- the term is often shortened in usage) finish.  The recognizable motif of a kiri-mon may be seen in the lower-left quadrant, and others appear elsewhere on the plate.  I believe the effects are achieved via the process I described in my earlier post.

 

Florian, as far as I know, the creation of amida-yasurime was often accomplished by painstakingly careful application of the chisel onto the plate, at least in the tsuba I'm familiar seeing this presentation in (e.g. some of the Owari province artists and groups, such as Yamakichibei, Toda, Fukui).  Attached is a Nidai Yamakichibei tsuba where the amida-yasurime was first chiseled into the plate, and then (perhaps?) there was some application of acid afterwards to soften the effect.  This is how it appears to me, anyway.   

 

[ROKUJURO]

According to Ford Hallam, the finer AMIDA YASURI was not chiseled, but scraped with a sharp tool. Another YAMAKICHI BEI:

A following YAKITE KUSARASHI treatment is very likely. 

[FlorianB]

10 hours ago, Robert S said:

Just a detail, but it's also worth nothing that in most cases acid etching doesn't result in a vertical sides groove or area, like you show in your illustration.  Generally, the exception to that rule is dutch mordant on copper, but that's a whole other story.  You're also unlikely to get a smooth surface left where etched, due to differences in metal composition, acid movement, etc.  The surface shown on the tsuba illustrated is pretty typical.

In my illustration I showed a very simplified version of the process. In fact I recognized myself, that there are different structures and tiny holes which I ascribe to non-homogeneous iron the Tsuba is made of.

[GRC]

As far as Yasuri lines go, I see the thick kiku-petal outline type and the irregular thickness + placement ones as being done with deliberate chisel strokes, while the very fine, regularly spaced ones would have been scraped by pulling out from center to rim using a "guide rail" that pivoted in the center of the tsuba where the nakago-ana would be.

Like @ROKUJURO said, Ford demonstrated this guided scraping technique in one of his video tutorials. 

I suspect there is no one on the planet who could free hand engrave each of those fine lines and be that consistent in their linearity and spacing. Personally, I wouldn't even bother trying to free hand it because I know I couldn't do it. 

[GRC]

Found it...

1- straight line guide on a practice plate

2- Wavy line guide on a tsuba in progress

[FlorianB]

Here are two specimen of yasurime enlarged which made me think they must have been etched and heated:

 

However, Fords video made me think - although he used the scraping tool on a copper plate.

[ROKUJURO]

Florian,

you could do the same on an iron plate without a problem. TSUBA are not hardened steel! The surface migt have been left a bit raw from forging, and additional YAKITE KUSARASHI did the rest.

You could replicate all this in my TSUBA forging workshop in July!

[FlorianB]

Sorry I’m a "Doubting Thomas"!
The longer I'm thinking over Ford’s video it seems a very time- and labour- consuming process if You do the same on an iron tsuba even if it is not hardened.

BTW: Wasn't there once a discussion if Tsuba consist of iron or steel?

 

Thus at least I plead for my method scraping the lines (like Ford shows it) into a lacquer coating and the etchant do the rest.

Quick and easy.

[ROKUJURO]

Florian,

there is no "fast and easy" in TSUBA making!

The discussion about iron/steel in TSUBA is finished. To have the desired function, it has always to be iron, never hardened steel (or cast iron, for that matter).

You can try your personal methods on my TSUBA forging workshop.

[OceanoNox]

6 hours ago, FlorianB said:

The longer I'm thinking over Ford’s video it seems a very time- and labour- consuming process if You do the same on an iron tsuba even if it is not hardened.

I have tried it, like Ford (hole in the middle of the tsuba, small nail in the hole to hold the guide, and file/scrape away! It's fairly quick, especially if you're not concerned about even spacing. Depth of the lines is another issue, but you can do it with a file or make several passes. 

 

6 hours ago, FlorianB said:

Wasn't there once a discussion if Tsuba consist of iron or steel?

Agreeing with Jean here. Scientific analyses of tsuba (either neutron diffraction, or plain hardness measurements) all point out to iron or wrought iron. 

[OceanoNox]

To add, I have tried to have "fancy" surface by leaving a tsuba in a 1000℃ furnace (electric) in air, for an hour or so. It does result in a surface that seems to have partially melted. It was completely uncontrollable though.

[GRC]

@FlorianB in the two examples you showed, the top one got the yakite heat treatment while the bottom one did not.

We see that in tons of Yamakichibei tsuba, but even the so-called Nidai smith, who is renowned for producing this amida-yasuri effect, apears to have eased off his use of yakite treatment over time, likely as trends shifted in the early Edo period and the lumpy-bumpy tekkotsu started to lose favor in place of a smoother, more regular surface which we see almost ubiquitously in mid and late Edo period tsuba (except for the "late Edo revival period" when tekkotsu came back on the scene). 

 

And as @ROKUJURO and @OceanoNox pointed out, it's pretty easy to scrape unhardened iron or steel plate using a hardened steel point on whatever tool you use to scrape it with... and repeated passes along the same guide position would get deeper grooves.

Scribing tools are used all the time to mark lines in metal work... this is just a decorative application of using a scribing tool.  

 

Re: "Fancy surface" for @OceanoNox... what type of metal were you using when you tried to get the desired effect?

I haven't tried it yet, but plan to this summer, but I strongly suspect you need the less pure grade of tatara steel that has much more variation in its composition. I think you'll get a relatively uniform effect using purer forms of steel like high grade sword steel, but a lot more variation in the position of crystal growth... maybe resulting in some of those "explosion" type tekkotsu we see most often in the works of the Yamakichibei "Low crossbar smith". Here's an example from one of his "ring of soybeans" tsuba.

This is just part of my overall hypothesis for now... I need to try it out to see what happens. 

 

[ROKUJURO]

1 hour ago, OceanoNox said:

To add, I have tried to have "fancy" surface by leaving a tsuba in a 1000℃ furnace (electric) in air, for an hour or so. It does result in a surface that seems to have partially melted. It was completely uncontrollable though.

What can be found in the literature about YAKITE has not been tested by the authors and is pure assumption. The surface of a TSUBA may indeed LOOK LIKE MELTED  (perhaps something like TOKA ME in Japanese), but it is definitely not! The melting point of pure iron is 1.538°C, wrought iron has some impurities, but almost no alloy metals content, so its melting point can be assumed to be about 1.480°C. 

In case you heat an iron object up to close to that temperature, it will deform on the underside as well, destroying any design that may have been created before, and it will take on the structure of the ground it is laying on. So this would never work! And the build-up of scale on the surface has not even been considered! 

[OceanoNox]

9 hours ago, GRC said:

what type of metal were you using when you tried to get the desired effect?

I used a piece of "steel", bought from an online shop called Haganeya. I suspect it is SS400, so low-carbon steel.

 

9 hours ago, ROKUJURO said:

The surface of a TSUBA may indeed LOOK LIKE MELTED  (perhaps something like TOKA ME in Japanese), but it is definitely not!

In my case, it is likely coming from non uniform scale growth. You can see in the photo what it looks like. I did the heating prior to anything else. So it messed up the seppa dai, and I was too lazy to shave it smooth... 

In the end, I soaked the tsuba in warm citric acid for a couple of days.

Edited yesterday at 12:48 AM by OceanoNox
added information

[ROKUJURO]

Thank you Arnaud!

Your results are exactly as expected! Higher temperature would have produced still more scale but not a "melted" surface.

[OceanoNox]

Jean, now my issue is that I used an electric furnace without option to control the atmosphere. I have no idea how it would look like for the same piece heated in a charcoal fire for some time.

[ROKUJURO]

Arnaud,

as far as I know, the Japanese swordsmiths of olden times did not have furnaces with a vacuum chambers....  

In case you can bury a workpiece deep in a charcoal fire, you will have more carbon monoxide and thus create less scale, but the higher the temperature, the more reactive with oxygen the iron will be. So scale will not be avoidable in any open fire.
Using water on the anvil while pounding will blast most of the scale away. 

It is generally overlooked how much material is lost in firewelding. The necessary high temperatures "burn" away the steel at a high rate, so only 25% of it is left in a blade after 12 to 15 foldings. However, there is a considerable difference between iron and high-carbon steel.

[OceanoNox]

22 hours ago, ROKUJURO said:

What can be found in the literature about YAKITE has not been tested by the authors and is pure assumption.

Back to that and the original idea of masking/etching, do you have a theory, or are there info about the acid used (I always imagined it could be vinegar)? 

From Ford Hallam's opinion that a lot of the texture was made by chisels and textured hammers (possibly anvils?), I wonder if this kind of mechanical texturing process was not combined with heat to force surface "damage" via oxidation. Then removal of that with acid, finishing touches, and controlled patination.

 

I suppose, aside from asking artisans who make similar stuff (are there any?), and barring the finding of documents detailing the process, we are left with our own experiments to confirm what kind of process could yield similar surfaces to the antique tsuba.

[christianmalterre]

This constant discussion about different types of charcoal and additives to achieve specific temperatures and cross-sectional heat is really starting to get confusing.
I think anyone interested in the chemical and physical changes in iron ores, steel and more or less refined forged iron will find what they’re looking for very quickly, given the wealth of material available in the literature.

I also think that by now every layperson knows that acids do not produce the desired effect seen here.
So why do we keep coming back to this utterly ridiculous idea that was written in a book some 30 years ago by several authors? ( none of them slightly expert in the field of metallurgy, no craftsmen, no working with the material ) - just experts in stilism and design....

Since when do acids work in such surface scenarios?
And since when does iron ore behave specifically in relation to the charcoal used?
Considering the extremely primitive capabilities available to blacksmiths, swordsmiths and all those other kind of smiths producing Tsuba in medieval Japan, I might still be able to imagine etching methods based on alkalis and repeated grinding and polishing....?!? ....but when it comes to acids, I personally don’t see that happening at all.

 

Sorry....

Christian

[OceanoNox]

23 minutes ago, christianmalterre said:

This constant discussion about different types of charcoal and additives to achieve specific temperatures and cross-sectional heat is really starting to get confusing.
I think anyone interested in the chemical and physical changes in iron ores, steel and more or less refined forged iron will find what they’re looking for very quickly, given the wealth of material available in the literature.

Literally not the topic here. We just discussed the use of heat with/without oxygen for the "melty" effect of yakite. Nobody talked about the possible effect of particular charcoal for this application. 

Yes, we are aware of the scientific literature on steel making tradition in Japan (in fact, I referenced a bit in my own posts elsewhere on this forum).

 

24 minutes ago, christianmalterre said:

I also think that by now every layperson knows that acids do not produce the desired effect seen here.

Apart from the fact that heating a tsuba for some time, and then putting the oxidized tsuba in acid did yield a similar surface to what's being discussed?

 

29 minutes ago, christianmalterre said:

I might still be able to imagine etching methods based on alkalis and repeated grinding and polishing....?!? ....but when it comes to acids, I personally don’t see that happening at all.

Use of acid is specified for patination of iron items (patinate a bit, then clean with some kind of acid, then patinate again), in books on traditional colouring methods in Japan. I am not aware of alkali, except to neutralize prior acid use. Do you have anything in mind?

[ROKUJURO]

Christian,

I apologize to be boring you with this subject, but we are actually only 'scratching the surface' of it. There are many factors which have to be looked at, and what actually seems like well-kept secrets may have been something so evident to the old TSUBA masters that they thought it not necessary to write about it. Of course, it may also have been business secrets!

All we can do - and what we are actually doing here (and I appreciate the scientific exchange with Arnaud a lot!) is trying to explain features which in the past have been described wrongly but early authors.

You are welcome to take part in this discussion, but you would need to know some chemistry facts. Please read this in German:

Eisen ist unter normalen Bedingungen sehr beständig gegenüber Alkali (basische Lösungen wie Natronlauge, NaOH). Im Gegensatz zu amphoteren Metallen wie Aluminium oder Zink, die sich in Laugen lösen, passiviert Eisen in alkalischem Milieu, was bedeutet, dass sich eine schützende Oxidschicht bildet. 

Reaktion von Eisen mit Alkali im Überblick:
Keine Normalreaktion: Eisen reagiert bei Raumtemperatur nicht mit verdünnten oder konzentrierten Alkalilaugen.
Passivierung: In Gegenwart von Sauerstoff und Alkali bildet sich eine schützende Passivschicht aus Eisenoxiden oder - hydroxiden, die das Metall vor weiterer Korrosion schützt.

Hochtemperaturreaktion: Erst bei sehr hohen Temperaturen (über 700°C) oder unter speziellen elektrochemischen Bedingungen (z.B. Bildung von Ferraten) kann Eisen von konzentrierter Alkalilauge angegriffen werden.
Alkali-Einfluss bei der Eisenerzverhüttung: In Hochöfen können Alkali-Verbindungen (aus Rohstoffen) die Eisenträger (Sinter, Pellets) beeinflussen, indem sie die Schmelz- und Reduktionsprozesse verändern. 

Zusammenfassend lässt sich sagen, dass Eisen im Alltag gegen Laugen weitgehend beständig ist.

Back to the main subject. Arnaud, you wrote: 

.....do you have a theory, or are there info about the acids used (I always imagined it could be vinegar)? 

From Ford Hallam's opinion that a lot of the texture was made by chisels and textured hammers (possibly anvils?), I wonder if this kind of mechanical texturing process was not combined with heat to force surface "damage" via oxidation. Then removal of that with acid, finishing touches, and controlled patination.

 

I suppose, aside from asking artisans who make similar stuff (are there any?), and barring the finding of documents detailing the process, we are left with our own experiments to confirm what kind of process could yield similar surfaces to the antique tsuba.....

I do not know what chemistry science was like in medieval Japan, but they had masking techniques (wax, URUSHI) and used them. Organic acids were available through all forms of fruit acids (did you ever experience the reaction of carbon steel with tomato juice?), vinegar, and other aggressive media like animal dung. These work certainly slowlier than our modern concentrated acids, and possibly needed another form of treatment like cleaning up in the process, but as time was not a limiting factor, it was possible.

It is also possible to produce nitric acid from potassium nitrate (KNO3) which was available in Japan.

Coming to texturing, Japanese craftsmen indeed used a variety of very specialized tools, and unfortunately, the different surface textures are often not recognized or described wrongly because we lost the contact to the craftsmen's realm. ISHIME, TSUCHIME, MIGAKIJI, KE BORI, KATAKIRI BORI, scraping, stippling, burnishing and many other techniques can be applied. 

All surfaces were patinated which helped to prevent a TSUBA looking "new", and at the same time, protect against corrosion (at least for some time).

And to answer your question: Ford told me that no living TSUBAKO could produce TEKKOTSU, so there is still some research to be done. I am on the track.....

[GRC]

8 hours ago, ROKUJURO said:

And to answer your question: Ford told me that no living TSUBAKO could produce TEKKOTSU, so there is still some research to be done. I am on the track.....

Well technically, Ford may not have been entirely correct at the time.

The Japanese smith Kazunari Nariki clearly rediscovered the technique and became quite proficient at it.

It was more along the lines of the smoother Kanyama and Ohno type tekkotsu, but not the more extreme "explosions" or "volcanic craters" such as the ones in the Yamakichibei Low-Crossbar smith's work I posted above.

 

Unfortunately that potential for gaining information is now gone because Kazunari Nariki passed away in 2022.

He was dedicated to sourcing sand iron from the specific regions where certain types of tsuba were made in order to achieve the different look of let's say a smooth black iron finish from Higo or the melty-looking lumpy surface of Kanayama-esque tekkotsu.

 

Utsushi of a Higo tsuba:

Utsushi of Yamakichibei with an otafuku-shaped guruma motif:

Utsushi of an early Hoan style irregularly spaced rays motif (a variant from the more typical guruma motif):

 

So that seems to hint at getting back to the idea of material composition as a significant contributing factor for the outcome.

I have a strong suspicion that the effect will not be effectively achieved by using modern produced mono-steels with fairly even distribution of component materials in the alloys.

i suspect using the right grade of steel from the right type of sand iron formed in a tatara will be a critical key to unraveling it all... 

but we shall see... i hope 

Edited 6 minutes ago by GRC

[GRC]

By the way, those images came from this forum thread:

 

along with this one as another Higo utsushi example: