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Beware of Torigoe's temper...


Ford Hallam

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I'm not a fan of 'Tsuba - An Aesthetic Study', as some of you gentlemen will know ;-). However, I do occasionally try to tease out reliable material.

 

Last night I was struck but how frequently Torigoe refers to the quality of the the temper of a tsuba's steel. What puzzles me is what he actually means by this. In technical terms 'temper' is result of relieving the absolute harness initially created (by quenching) so that a better balance of toughness and hardness is obtained. Essentially the steel is reheated very gently to relieve some of the internal stresses and thereby restore some flexibility and toughness in the structure.

 

Is Torigoe implying that it's possible to discern this state by eye and touch, through a patina? And, does anyone know of any scientific analysis' that provide any data relating to either carbon content or harness of the sort of tsuba Torigoe most recommends?

 

I ask about the analysis because he offers some very specific details of carbon content and the corresponding hardness. (pp21 'aesthetic study)

 

I think this is a very important detail to examine because if it is actually not technically accurate we are merely left with Torigoe's subjective feeling about the material qualities of the objects he's thus describing. Subjective descriptions can be quite useful but we need to ensure we don't accord them the same status as verifiable facts.

 

I look forward to hearing other thoughts on the matter.

 

kind regards,

 

Ford

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I'm reading the translated version, I don't have a copy of the original Japanese. I'd appreciate a scan of a few pages if that was possible....anyone?

 

Having said that, the problem remains that for most non-Japanese students this particular book is quite heavily referred to and if this is a mistranslation it's a pretty serious one.

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But by tempering, does he mean annealing...or is it used the incorrect way most of us do, to mean the actual quenching/hardening process?

I know it is wrong, but it has become accepted to mean the quenching process.

 

Brian

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Yes, Adam is quite right....however we might define this term the ability to discern it by means of hand and eye is beyond us mere mortals. Perhaps Mr Torigoe was a Jedi... ;)

 

Annealing, however is only correctly applied to non-ferrous metals.. When we speak of ferrous metals the correct term is 'normalising' as it's not quite the same result nor process.

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I never knew that. I thought annealing was anytime any metal was softened by heat (and by quenching with copper) making the molecules realign and making the metal workable again. Can you explain the difference between normalizing and annealing, or post a link that explains it. Does it have to do with the difference between work hardening and quenching?

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Actually, annealing is indeed proper when used with steels....Annealing and normalizing are slightly different:

 

from: http://www.efunda.com/processes/heat_treat/softening/annealing.cfm

 

 

"Full Annealing

 

Full annealing is the process of slowly raising the temperature about 50 ºC (90 ºF) above the Austenitic temperature line A3 or line ACM in the case of Hypoeutectoid steels (steels with < 0.77% Carbon) and 50 ºC (90 ºF) into the Austenite-Cementite region in the case of Hypereutectoid steels (steels with > 0.77% Carbon).

 

It is held at this temperature for sufficient time for all the material to transform into Austenite or Austenite-Cementite as the case may be. It is then slowly cooled at the rate of about 20 ºC/hr (36 ºF/hr) in a furnace to about 50 ºC (90 ºF) into the Ferrite-Cementite range. At this point, it can be cooled in room temperature air with natural convection.

 

The grain structure has coarse Pearlite with ferrite or Cementite (depending on whether hypo or hyper eutectoid). The steel becomes soft and ductile.

 

 

Normalizing

 

Normalizing is the process of raising the temperature to over 60 º C (108 ºF), above line A3 or line ACM fully into the Austenite range. It is held at this temperature to fully convert the structure into Austenite, and then removed form the furnace and cooled at room temperature under natural convection. This results in a grain structure of fine Pearlite with excess of Ferrite or Cementite. The resulting material is soft; the degree of softness depends on the actual ambient conditions of cooling. This process is considerably cheaper than full annealing since there is not the added cost of controlled furnace cooling.

 

The main difference between full annealing and normalizing is that fully annealed parts are uniform in softness (and machinablilty) throughout the entire part; since the entire part is exposed to the controlled furnace cooling. In the case of the normalized part, depending on the part geometry, the cooling is non-uniform resulting in non-uniform material properties across the part. This may not be desirable if further machining is desired, since it makes the machining job somewhat unpredictable. In such a case it is better to do full annealing."

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Even if he made the tsuba in question, he would only be guessing at it's carbon content. And, If he had been the person doing the 'tempering', he would still only be guessing at it's hardness/toughness.

 

If, he knew the tsuba was made of 'sword' grade steel, and had spent the multitude of hours trying to chisel/saw through it, he may be able to say that "Yes indeed, this one was a bugger to cut through, regardless of how much I annealed it".

And then, could have a close guess.

However, holding, and maybe tapping on, or any other test you may do on a finished, patined, tsuba, would just be a guess, at best. Even if you were a Jedi.

I have been making my own iron and steel for my tsuba & blade work for a little bit now. I would think that the Japanese likely use the not so pretty parts of any bloom for making tsuba. Even after doing 6-8 folds, this material can have many impurities in it. This can make them very tricky to work with, when doing sukashi especially.

 

If Torigoe, had been able to do some form of stress test on a few thousand tsuba, he may have been able to make a better guess due to where it was made, or by whom. That was likely what he was doing. Without the testing.

He may have been able to tell a tsuba had been 'heat treated' in some way, that could have resulted in a tempering process. And, from this, may guess that it is tougher in some way then another.

As to carbon content, he may have had knowledge of the normal construction/forging process of the tsuba school in question. This could give him a close guess on the carbon content. Or he may have devised a 'ring' test of some kind.

but, that wouldn't be very scientific.

Even if he were spark testing those tsuba on a grinder, it would still only be a close guess.

 

?????? Mark G

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Hi Ford,

 

Thanks for posting such a interesting topic for discussion. I can generally tell if a tsuba has underwent additional heat treatment (aka annealing) in Japanese yakiteshitate because many of the sukashi or other details including even the mei would appear to be melted almost like butter. You can often find this on Yamakichibei tsuba. Steve W. would be a good person to ask for some additional examples. I think these tsuba have one of the hardest iron because of the additional heat treatment. Very close in hardness to Yamakichibei tsuba are the Saotome school tsuba as well but these tsuba I don't think had any additional heat treatment. This might be because of the carbon content or other factors but I am not sure. Here is a Yamakichibei tsuba in my collection which had heat treatment applied. Notice the melted appearance of the ko-sukashi and mei. If you look under low magnification the surface is shiny. This might also be a effect of the heat treatment. I think some of Torigoe's statements are subjective but I do think there are tsuba with harder iron then others. Hardness being just one of many other characteristics of the specific iron used to make the tsuba.

post-1126-14196828197218_thumb.jpg

 

 

 

Yours truly,

David Stiles

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Thanks Chris, for the details on annealing vs normalising. I was just thinking in terms of workshop practice as would have been usual practice 'back in the day' using forge and where such distinctions are more generalised. :)

 

David,

 

Thanks for the image of the Yamakichibei. It illustrates exactly part of the problem Torigoe's ideas create. We actually don't know that this type of surface was really created by means of melting at all. Just because it looks a bit like melted butter doesn't convince me it was. In fact when you raise steel to the sort of temperature where the surface begins to melt you get carbon burn-out and a resulting coarse surface. I'll post some images of the effect tomorrow. In my view 'yakishitate' is a term best used to describe the appearance but not necessarily the actual process used. This sort of 'poetic' terminology s fairly common in Japanese art.

 

But just as a mental experiment can you imagine how a tsuba-ko might have actually gone about melting the surface of a tsuba to create this soft melted appearance. Bear in mind the melting point of steel is more than 14oo degrees C and the smith would need to ensure that however the tsuba was manipulated or held didn't leave any marks on the melting surface. In addition, consider how risky such a procedure might be in terms of melting the whole piece because keeping just the surface at melting temperature might be a bit tricky. ;)

 

Again, references to hardness, "Very close in hardness to Yamakichibei tsuba are the Saotome school tsuba", are not as yet supported by scientific testing, nor is the supposed carbon content. This is merely an unsubstantiated assertion. :dunno:

 

As for your Yamakichibei tsuba, if it was indeed hardened would that not have posed something of a problem when sekigane was added later? This type of alteration work and the addition of ryo-hitsu, after the initial making, is quite commonplace after all.

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Hi Ford,

 

On the issue of the ryo hitsu-ana of my Yamakichibei tsuba they are original from my in hand observation of the tsuba and were not added after the yakiteshitate process. I think this can be observed from looking at the inside surface of the openings. In regards to the sekigane they were added much later likely after the tsuba was remounted on another Nihonto.

 

If you had not notice in the my last post I presented just anecdotal evidence from looking at tsuba in my collection about the hardness of different schools of tsuba without any strong scientific and empirical evidence. To answer your original request I think in the world of tosogu that is all you have from Torigoe's time until now. In the end I think it would be a really fun PhD dissertation to study such a topic to produce some real scientific evidence in this field of study. I think the problem with trying to recreate the masterpieces of old in your backyard like Mark G. is that in the end you don't have a master showing you the fine details of forging and the finishing (ex. yakiteshitate etc.) of the tsuba making process along with the correct materials to use. For example with tamahagane there are many different grades based upon carbon content likely some where used for tsuba making while others not so much. Alternative idea would be that different grades of tamahagane were used in specific ratios. The use of nanban tetsu "southern barbarian iron" and its use in making Nanban tsuba adds another dimension to the issue. This is not to say that Mark G. haven't been able produce any fine tsuba.

 

 

 

Yours truly,

David Stiles

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Here´s an quite interesting part of an article/Published in JSS/US Volume 25 No.1 (1993)-by the late Dr.Tom Hoopes,who wrote an very enjoyable article(as far as i do know,part of his doctorial Dissertation)named: „A Study of Japanese Sword Blades“...

I just cite:

The(Iron/Steel) of the Japanese sword is not in fact made of well-tempered steel,for it is not really tempered at all!The word „temper“is widely misunderstood and misused.Popular writers frequently use it as thought it meant „hardened“.On the contrary,it actually means „softened“,“lightened“or „reduced“as in:“God tempers the wind to the shorn lamb“;“Temper Justice with Mercy“.In the occidental metallurgy of steel,the word is quite properly used in just this sense.When a smith forges a piece,he hammers it to shape,heats it to a bright cherry red,then plunges it into water or oil.This brings the whole object to a state of near-glassy hardness.Next he cleans and polishes the item and again heats it,slowly and carefully.As he does so,colours begin to appear on the polished surface,first yellow,then brown,then purple,and finally blue.When he judges from the colour that the right temperature has been reached,he again plunges it into a cold liquid.This „sets the temper“,that is,it reduces the extreme hardness caused by the first quenching to a proper combination of hardness and toughness for whatever use the item is intended.

With the Japanese sword it is not so;it is never tempered.After being shaped the blade is covered with an insulating mud,which is removed all along the cutting edge.It is then heated,once and for all,to the correct hardening temperature,and quenched.The edge becomes permanently hardened to a degree akin to that of a razor,the rest of the blade protected by it´s insulating encasement,cools much more slowly,and ends in an almost annealed condition.

 

If we do examine this-and put this theory to equally the production of Iron Tsuba here-there seem to be plenty of further possibilities how and in which degree an Tsuba may have ben produced/individual to the time,school and artist.

Additionally-please do not forget-that still you do have the possibilities of latter application of polish,acids and abrasive work....

 

The reader may judge for himself here...

 

Christian

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The use of nanban tetsu “southern barbarian iron” and its use in making Nanban tsuba …

To divert a little from Ford’s original submission, may I take issue with the above statement of David’s? What evidence has he for this: I personally believe it to be quite unfounded. John L.

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Hi Christian - Perhaps Dr. Hoopes was working from incorrect material as I believe Nihonto are tempered(yaki-modoshi) after quenching(yaki-ire). It is outlined in Yoshihara's "The Craft of the Japanese Sword" on page 92.

 

David, I believe Ford's comments meant that if some tsuba were hardened, it would be very difficult to add sekigane or hitsuana at any time after they were made. Any work to fit the tsuba to another sword would be almost impossible if the tsuba steel was hardened to any degree. Files don't cut, saw blades don't cut and punches would have a hard time moving hardened steel.

It seems to make little sense to harden tsuba steel.

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David,

 

I think we agree then, that in essence much of what is taken at face value in the various 'technical' descriptions of ferrous tsuba is merely guesswork and not based on any empirical data. This being so I suggest we dispense with them entirely until such time as we can reasonably say we actually have a vague idea of what we're talking about. :D The real problem with the continued use of these sorts of unexamined ideas is that they stand in the way of any real investigation in that they seem to define the territory in advance. In essence, the entire subject is built on unverified guesswork. As you say, this would make a very interesting and valuable basis for some serious scientific analysis.

 

As has been pointed out, we don't know exactly what methods old masters used but we do have a pretty good idea about how metal behave under certain conditions. One being that steel doesn't reach melting point and begin to soften like butter or wax :D that much I'm pretty certain about. That there may be all sorts of other possibilities is self evident but that also shouldn't open the door to speculations that are not based on any empirical or physical evidence.

 

And don't get me started on 'tekkotsu'.... :roll:

 

edit to add;

 

Yes, Lee is correct when he points out I was referring to steel tsuba in general and not specifically to your Yamakichibei. :)

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And don't get me started on 'tekkotsu'.... :roll:


Why not? ;) There is an intersting article by Andy M. on tekkotsu (among other things) in Momoyama armour and tsuba:
* link dead *

I am sure most of you have read it already, if not, here it is :)
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Mariusz,

you're a very naughty man ;)

I've read Andy M.'s article and wasn't particularly impressed I'm afraid.
 

Folding iron greatly increases resistance to ballistic and notch-impacts, by dissipating the impact
energy from effectively a point or line source, to a greater surface area provided through
successive planes of laminated material that tend to shear or delaminate rather than fracture.

 


He then illustrates this principle by reference to a laminated compound which is quite different to the material that results from simply folding and forging steel to refine it. I'd suggest that this point is therefore unfounded with reference to the subject he is writing about.

His next assertion;
 

Tekkotsu may be defined as segregated areas of high carbon content, formed as a result of
a process of successive episodes of heating, folding and hammering of an iron plate.

 


It may well be defined in this way by some people but as yet we have no actual scientific analysis to corroborate this notion. So this point is just another guess. I actually don't think tekkotsu are higher carbon content at all but lower carbon.

His conclusion;

 

The combination of the laminated plate of a tsuba, with heterogeneous carbon is thus a
very effective crack arrestor.
is therefore unwarranted and not proven.
 
Kokatchushi tsuba would then be made from scrap metal used in the production of armor, which may have been folded, but generally more iron-like in feeling and appearance.

 

I assume here he means iron-like in appearance and feeling (?) as opposed to steel -like in appearance and feeling. Bear in mind we're generally talking about patinated or rusted material. How exactly do they differ in appearance? From my own experience of sourcing both from scrap yards I can assure anyone that merely looking and feeling the stuff is not helpful in identifying either material. So, another meaningless point. :dunno:

He describes a menpo thus;

This mempo (face armor) dates to the Momoyama period. It was likely made in Western Japan by a Haruta school smith. It is thin, light weight and the steel is very hard with a high carbon content.

 

Unfortunately, and to the detriment of the article's credibility, he doesn't cite any evidence or analysis' for this though.

he adds;
 

Tekkotsu if present, were often filed down to facilitate lacquer application.

 

but we have no way of knowing how he actually knows this. It is merely another guess based on absolutely no evidence. Surely assertions like this need to be qualified with some evidence.


Since tekkotsu appear in the mabizashi, they are likely also present in the hachi plates, and thus could also have added to the energy absorptive qualities of the metal.

 

And how has it been established that tekkotsu (which itself hasn't even been accurately defined as yet) has "energy absorptive qualities" ?

The article then passes to a discussion on the quality and production of plate used in the manufacture of armour. Here Andy is on firmer ground with his explanations of the types of battle damage that is often seen, particularly underneath later additions. Unfortunately he soon reverts to making unsubstantiated assertions about steel.


One outstanding attribute of Haruta hachi dating to the Muromachi period is that they are composed of very thin dense plates

 


How does one distinguish a very dense plate from a less dense plate if they both have similar physical dimensions? ie; both the same thickness. For this statement to have any meaning we'd need to compare the actual weight of this apparently very dense plate with a similar plate that had the same thickness but was less dense. I can't imagine how Andy has managed this tricky operation so that he can make this claim.


It is possible that some Haruta kabuto are either not folded, or are folded to such a degree that individual laminations are not apparent. It is clear however that the metal is very dense and hard, suggesting a high-carbon steel. One might even compare the tensile qualities of Haruta hachi to that of stainless steel

 

In the absence of any analysis of the steel this is yet again merely guessing, especially as he has no comparative steel of known composition and properties to make his comparison to. And there's that word 'dense' again. Sounds serious but is actually meaningless in this context. One might compare Haruta hachi steel to stainless steel but as there are so many types of stainless steel it's all a bit vague. And once again not really making a comparison of any know qualities of either material. A pointless statement.

The following paragraph begins thus;

In addition to using steel with a very high tensile strength, Haruta kabuto....

 

If this has been proven by means of some actual analysis or materials strength testing we're not made aware of it. As it stands it's just another of those unsubstantiated assertions, or guesses. Notice, though, how each new point builds on the previous unsubstantiated guesses.

Another kabuto is described thus;

The steel is light weight, high carbon with a grayish brown patina on the inside.

 

but sadly no reference for this analysis is provided so I'm forced to assume it is not verifiable. Certainly, as it stands it must be dismissed as heresay.

His next supposition is the following;
 

It can be surmised that the Myochin hachi were composed of a softer iron rather than steel

 

This deduction is apparently based on his interpretation of various bits of damage to Myochin kabuto he's seen. Frankly, I don't know that anyone could be all that sure of something so specific based on such variable evidence.

The next kabuto is described like this;
 

In contrast to the previously mentioned Haruta kabuto, this hachi has 32 flat plates, more rivets, and is made out of a softer steel or iron with a more absorptive quality. It is also much heavier.

 

Here he seems uncertain as to whether his previous assumption about Myochin kabuto being softer iron rather than steel is always applicable. :roll: That this one is much heavier also tells us nothing meaningful about the material's qualities only that there is more of it. But again we have a claim about the material composition and it's material qualities neither of which have been proven.

I have to agree wholeheartedly with this comment of his though;
 

We think that a scientific study focusing on the comparison of physical qualities of metals from both Muromachi tsuba and armor could yield enough concrete information to revise and link the two disparate chronologies, and help better date and categorize the early iron tsuba that are the subject of so much ongoing controversy.

 


If such a study were made and the results made available he might be able to base his ideas and theories on some actual evidence. And the references cited at the end don't do much to inspire a great deal of confidence in this article as a piece of useful research, in my opinion. Rather, it simply adds more unverifiable assertions to an already confused area of study, namely the qualities and composition of early armour and tsuba.

There may well be useful research available that does provide the sort of data we would need to see but by not accessing it nor referring to it he has undermined the credibility of his article, I feel.

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Ford,

 

thanks for this critical comments on Andy's article - it surely contributes to my learning :)

 

But I fear, that we might have strayed somewhat from the topic, even though the tekkotsu discussion is relevant to some degree....

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There is no real 'tekkotsu' discussion until we know what it really is. Until then we're just making stuff up.... ;)

 

OK, let us adopt a more leisurely approach to tekkotsu - "iron bones" are lumps or streaks of iron projecting from the rim and the plate (of a tsuba), and while we do not know exactly what they are made of (high carbon or low carbon iron) some of us like them a lot.

 

Christian, I love this pic :clap: This little guy looks like he could know what tekkotsu is :rotfl:

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Hi John,

 

To restate again my main point of the earlier post and to answer your question the evidence is anecdotal at best and not scientific. I collect what I like to see I don't collect tsuba for scientific study I collect them as fine art.

 

 

 

Yours truly,

David Stiles

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Hi Gang,

This is indeed a great talk.

In the past couple years, I have done some extensive research, and testing into fire treatments of tsuba. Mostly in my quest to re-create "bones".

I have tried these treatments on grade 1 Japanese & Chinese Tamahagane, lesser grades of these, all made the traditional way. Many modern steels, and more recently, many grades of my own iron & steel.

I will publish all this sometime soon, but right now I'm so busy making stuff, that I don't have the time or inclination to write it all up.

Most of these tests involve heat treatment to high temps, and acid baths after, to remove the fire scale.

Then the used of abrasives, and back again for more testing.

The tsuba, I have completed using these methods do have a certain "look", much like Dave's tsuba does.

That was what I was talking about with reguards to experience of knowing how some schools did their finish work.

But, it would still be just a guess, as to the temper, and carbon content.

 

These heat treatments are very difficult to do on thin sukashi. Solid plates are easier. But to get anywhere near melting your plate, forget it. The "look" is created by the acid & abrasives used after. It does make for a nice finish. With a solid plate you can get close to "that" hot, but then you risk having to straighten up the warp you may get. It just isn't worth it.

 

Can you make bones? Yes. There are a few ways. But it is impossible to recreate the 2-600 yrs of rust & wear.

 

One day I will do a big write up on all the work.

 

With this "Rabbit in the moon" tsuba, I hand chiseled all the sukashi, and did multiple heat/acid treatments. You can see it has a bit of that "melted" look. This is my steel.

post-99-14196828291942_thumb.jpg

 

On this one, I did the same. It is grade 2 Japanese tamahagane. It has less of the melted look. But I could not let it get as hot.post-99-14196828303599_thumb.jpg

 

This is modern, mild steel. The same process. It gives a nice look.post-99-14196828306393_thumb.jpg

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Exactly, Lorenzo :D

 

Until we know exactly what these appealing lumps and striations are made of, and how thay are formed in the steel, all we can say is we might be able to simulate a similar effect.

 

As I see it there are a number of problems with the 'lumps of high carbon' theory. This idea is a bit like raisins in a cake but in practice one wonders how these lumps retain their 'roundness/lumpiness' when the forging process to process these lumps into the plate would by necessity flatten them out. Similarly, even the most limited amount of working of bloom steel will result in a thin linear structure.

 

Consider also that high carbon steel corrodes more easily than low carbon steel and iron. So it the lumps are a result of various acid etching, forced oxidising or corrosion processes over time then it's probable the 'lumps' are lower carbon areas.

 

But, as has been pointed out, we enjoy the effect, however it was produced. :D Until we know what they are, though, we're just guessing in the dark.

 

Thinking about it....I may have an idea or three to test 8)

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Until we know exactly what these appealing lumps and striations are made of, and how thay are formed in the steel, all we can say is we might be able to simulate a similar effect.

 

And we don't even need steel. I did it in silver :lol:

 

post-801-14196828349452_thumb.jpg

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