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How many polishes?

jezah81

By jezah81
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jezah81

Posted
Posted

How many times can a blade be re-polished generally speaking until it is deemed a "tired" blade? Like 5-10 times, 10-20 times.....etc?? I understand there are a few variables such as the amount of niku a blade has etc... but a rough estimate would be good enough.

 

Kind regards,

 

Jeremy Hagop

Brian

Brian

Posted
Posted

Jeremy,

 

I think that is impossible to say, even an estimate is not possible.

Some blades have thicker skin steel than others.

The amount of polishing that needs to be done depends on the damage. Pitting? scratches? Just muted hataraki?

There is no such thing as a common amount of metal that is removed with a polish. Some just need to be renewed, others need a full polish from the first foundation stones. Do chips or nicks need to be removed?

It all comes into play.

One sword might take 10 polishes, while another might be tired after 2 if there was a lot of work necessary.

 

Sorry, but I think that is a question that can't be answered.

 

Brian

nagamaki - Franco Veteran

nagamaki - Franco

Posted
Posted
Jeremy,

 

I think that is impossible to say, even an estimate is not possible.

 

Brian

 

A "good polisher" from experience can tell with amazing precision how many polishes are left on a particular blade. What a polisher cannot predict is unseen kizu hidden beneath the surface that might become exposed.

remzy Rising Star

remzy

Posted
Posted

Funny you should mention this Franco... i was just thinking about something regarding hidden kizus this morning.. I was thinking, has anyone ever used metal detection tools* on high end nihontos as to detect defects hidden in the metal? Or would this be unappropriate? hmmm ..

 

*(like the tool they use to detect cracks in metal pilars of oil platform, for exemple)

 

Regards,

Remy

Ted Tenold Mentor

Ted Tenold

Posted
Posted

The number of polishes is irrelevant to the procedure. One has to always remember that most consider polishing a restoration process, but really it's a conservancy process. It is the job of the polisher to remove only the minimal amount of metal that will preserve the blade and identify it in shape and activity. The invasive nature of the process at most every level has a detrimental effect on the life of the sword. So really it's not how many polishes, but how much invasion will the blade tolerate. And on that level, it doesn't matter how much it will tolerate, the original form of the blade is lessened with each polish as well. So even if it will not become tired by intrusion of the construction (i.e. exposing core steel), it becomes tired in it's keijo, or form, which is the single most important identifier of a swords identity.

 

The original health, dimension of the sword, it's construction method, as well as the skills that the smith had in creating it are the first factor. Swords made in certain construction arrangements will tolerate more invasion. A sword comprised of very good steel throughout the cross section will tolerate more than one of kobuse (hot dog and bun) style constrution. The Rai school is often recognized by the presence of "Rai Jigane" or "Rai Hada" which are areas of looser construction mostly exposed over time in polishing. It's not a derogatory trait though, because the quality of the steel throughout the swords is very high, and it's an acceptable characteristic of the school. However, more healthy Rai's I've seen, such as one I saw that was Tokubetsu Juyo, had none at all, which threw my kantei or it off because it's been drilled into me to look for sporadic looser hada. The Tadayoshi school in Hizen made swords in the Rai style, and the hada is brilliantly done. But it also required very high quality iron (read that as expensive) and was labor intensive to forge to obtain that fine luster, so the conservation of that material meant that they made the kawagane very very thin. Hizen blades are therefore notoriously "thin skinned" and even one stone can burn through it.

 

Therefore, the next factor is the skill and knowledge of the polisher, and EVERY polisher that ever touched the blade previously. He must be able to identify the sword and then accordingly he must be able to see any problems in shape, health, construction, flaws, and correct, repair, and implement a plan for restoration. No small task given the conditon that some swords arrive in. Is it a Rai, or a Tadayoshi? If it's a Rai, whose? What period? What region? Yamashiro? Nakajima? Believe me, that's the short list of questions. In some cases he may leave problems if correcting them will compromise the blade in such a way that removing/correcting will be worse than just leaving it. The skills, or lack thereof, of those that worked on it everytime before are critical. Bad decisions or improper methods cannot always be corrected. So again, it comes down to being as least invasive as possible. Some make good decisions, some bad. Either way the blade suffers, just not as much in the former as the latter. The process can be fatal in the first or the twentieth polish. A good polisher might even turn down polishing a sword if he thinks that even in the most conservative of efforts, the blade will be fatally altered.

 

Last, and influencial on the polishers abilities, is the *preservation* of the blade. How extensively has it been used? Was is used in combat? How much? Carried only on special occasions? Stored in an armory? Buried in a back yard? Left on a wall and forgotten? A good polish on a sword can last well into a century or more if maintained, handled, and stored prudently. That negates any subsequent need for more invasion through polishing, and makes it much less invasive when it finally does become necessary.

 

Swords that have been preserved to the utmost degree can stand in oppostion to what we normally *imagine* them to be because we see comparible examples that have not been as deftly or skillfully maintained. Seeing swords from the Heian and Kamakura period that are as large (or larger) than many gendaito and shisakuto is a stunning reality check on what preservation and conservancy can accomplish.

Ted Tenold Mentor

Ted Tenold

Posted
Posted

 

A "good polisher" from experience can tell with amazing precision how many polishes are left on a particular blade. What a polisher cannot predict is unseen kizu hidden beneath the surface that might become exposed.

 

 

I'd actually offer the reverse of this. There's no polisher I've yet met with a crystal ball that can tell how many polishes a blade will tolerate. Polishing is not a wholesale "start with this stone" process, and what will happen to the blade in the future will determine what starting point will be required.

 

Kizu, although I'd agree they cannot be completely predicted, there are blades that "run to kizu" and therefore are a preliminary suspect. Yoshimichi school blades are an example of them. So being able to identify the sword will give the polisher the ability to predict at some level. Also there are techniques for searching for them prior to the polishing process. Identifying construction will point to anticipating (I hesitate to say "predict")possiblities as well. How the kizu are addressed (if possible) is the important factor if they are found.

Ken-Hawaii Grand Master

Ken-Hawaii

Posted
Posted

Brian, I think that Ted's explanation of polishing should become a "sticky," because it has so much useful information. Great job!!

 

Rémy, yes, there are several metallurgical techniques that could be used to search for hidden kizu, but I'm not sure exactly how we'd go about it. There are many detailed procedures to look for cracks & weak points in steel plate/pipes/etc., but how do those apply to a hand-forged blade? I've worked in the field for about 40 years, & I'd hesitate on NDT (non-destructive testing) because I'm not sure how to interpret what I see....

nagamaki - Franco Veteran

nagamaki - Franco

Posted
Posted

 

A "good polisher" from experience can tell with amazing precision how many polishes are left on a particular blade.

 

There's no polisher I've yet met with a crystal ball that can tell how many polishes a blade will tolerate.

 

Ted, crystal balls set aside are you absolutely sure?

Jean

Jean

Posted
Posted

Jeremy,

 

Getting back to your question, I have no picture of your entire blade but I can assure you from what I see that there is enough of Hamachi/Munemachi to have a polish done :) :)

Ted Tenold Mentor

Ted Tenold

Posted
Posted

No, I haven't met them all yet. :-) But devining with some precision that a sword will take x number of polishes in it's life is a bit of a moot statement. We'll never be around to verify it, and if a sword is getting polished that much in a single lifetime, then something is seriously wrong.

 

From a purely logical approach though, I'd offer this; A polish on a sword doesn't always necessarily start from the coarsest stone which removes the greatest amount of metal than any other. Therefore, if the blade were in a state that required starting with one finer (or shall I say *not* as coarse) then more "polishes" could be endured. How many? Well, again, depends on the preservation efforts, the construction of the blade, the skill of the smith in controlling his materials, and the skills of all the polishers throughout the swords existance.

 

Again, I'd offer my Tadayoshi example. They are thin skinned. But how thin and where is it thinnest or thickest on the length of the blade? Sure, a polisher can look at a blade and say, "This sword is very healthy", but the skill of the smith in controlling his materials will decide whether the kawagane is equal throughout the length and breadth of the blades surface. However a shallow spot in the kawagane can't necessarily be seen, though it can be anticipated. In looking at the construction one might see either konuka hada in the shinogiji, or perhaps areas of masame (and/or dull colored steel) drifting down. The former would indicate a healthy kawagane as it hasn't started to fade into the side of the sword with polishing. Masame creeping deeper into the shinogi would indicate that the kawagane is deteriorating. But even if the konuka looks healthy, there could very well be an area that is shallower than the next just waiting to expose shingane despite that konuka in the shinogi.

 

Pardon me for saying so, as I really don't intend to appear argumenative, but your statement is somewhat contradictory in this regard too. A polisher (even a good one) *cannot* predict with any precision how many polishes a sword will take, if they cannot see hidden kizu. Burning through kawagane is literally installing a flaw due to not being able to see how shallow or deep the shingane is in the blade. Sure, assesments can be made on the individual health (or lack of it) of a sword, and therefore an educated Occam's razor type judgement made, but that's for the next polish not the one following that. Hidden is hidden no matter how healthy it looks from the outside. If it was unexpected, it was unpredicted.

Jacques D. Grand Master

Jacques D.

Posted
Posted

Hi,

 

I've an article talking about tsukurikomi. this article contains some pictures wich shows the disposition of the hard steel and the soft one.

 

These pictures confirm that Ted says.

 

img3344hk1.th.jpg

Brian

Brian

Posted
Posted

Thanks Ted, that is an excellent article.

Would like to add it as an article in the archive section. Always good to hear it from the people who deal with it on a daily basis :)

 

Jacques, that is also an interesting article you have posted there. Surprising analysis of that Sukesada blade, and explains a lot of the flaws and general faults we see in various blades.

I guess we would all like to think that these blades were forged according to the ideals pictured, but when forging them, it is all to easy to have something go wrong and end up with an internal crosss section far from what was planned originally.

 

Thanks,

Brian

Jacques D. Grand Master

Jacques D.

Posted
Posted

Hi,

 

Interesting book, I would like the name of that book.

Is it about sword metallurgy specifically?

 

 

It's not a book, it's an article which was written in 1981 by Harvey Stearn in the Bushido journal.

 

You can also look at here especially the paragraph "Japanese sword from ancient times". I think that is instructive and show the necessity of the smith's skill.

Ted Tenold Mentor

Ted Tenold

Posted
Posted

Interestingly enough, Harvey Stern once did a bunch of cross sectional studies on sword that were tired or damaged beyond repair. They are a great example of the different constructions used by smiths, and demonstrate the concerns of over polishing and hidden kizu.

 

I photographed them some years back for my library, but I didn't take high resolution images unfortunately. My friend Keith re-shot many of them later in better rez and I believe they're still over on Rich Steins index, but I can't access the page right now for some reason.

 

Here's one that I originally shot. This is Kobuse Kitae construction.

post-44-14196741064878_thumb.jpg

nagamaki - Franco Veteran

nagamaki - Franco

Posted
Posted

Pardon me for saying so, as I really don't intend to appear argumenative, but your statement is somewhat contradictory in this regard too. A polisher (even a good one) *cannot* predict with any precision how many polishes a sword will take, if they cannot see hidden kizu. Burning through kawagane is literally installing a flaw due to not being able to see how shallow or deep the shingane is in the blade. Sure, assesments can be made on the individual health (or lack of it) of a sword, and therefore an educated Occam's razor type judgement made, but that's for the next polish not the one following that. Hidden is hidden no matter how healthy it looks from the outside. If it was unexpected, it was unpredicted.

 

 

As for contradictory statements, yes, unseen kizu are unpredictable as I have already clearly stated. I think most people can understand this concept without having to spell it out. There will always be issues when swords are in poor condition in relation to knowing how they will turn out. However, when minor foundations need to be adjusted and little else structurally and only a "surface" polish is needed, a good polisher will know with amazing predictability that a sword made by swordsmith X can be polished five more times or ten more times before reaching core steel.

 

Look Ted, we're in agreement on all tech points, we actually agree on unpredictability, we don't agree on predictability, let's leave it at that.

Keith Larman Contributor

Keith Larman

Posted
Posted

Here's another cross-sectional photo from the same set. I repolished the face and shot it under different lighting and also edited it in Photoshop in different ways to make different things visible in the image.

 

One of these days I need to resection them all and shoot them. Just fwiw.

post-34-14196741065629_thumb.jpg

Keith Larman Contributor

Keith Larman

Posted
Posted
Hi Keith and Ted.

It would be interesting to have details about the school and age of the swords sectioned, if available and if sharing of such info allowed.

 

Well, since I happen to have that very nakago on my desk... here's a quickie scan from my inexpensive all-in-one scanner/printer/etc.

Keith Larman Contributor

Keith Larman

Posted
Posted

Just to add an observation -- I posted the particular cross sectional picture because it illustrates something you also see in the other images done from cross sections including articles already referenced. More often than not the skin steel is rather thin and when you cross section you'll see that the subsequent forging distorts things quite a bit. Sometimes the core steel is dead center. But usually the core steel seems to wander closer to one side more than another in points of the blade. Remember that after that critical welding to create the laminated blank the entire thing is drawn out. That forging and then subsequent filing by the original smith sometimes seems to leave you with areas where the skin steel is a lot thinner than you might have thought. In the photo I posted notice that one side has virtually no skin steel left. I'm pretty sure the blade was sectioned because core was showing elsewhere on the blade. It has been polished a few times obviously. And the hamon is a bit low. But there is still a fairly decent hamachi and munemachi. So it hasn't been polished way too much (by most standards). But clearly the blade is already tired. If you were looking at a shinto piece with the same hamachi and mune machi and when you look down at the nakago you'll see there isn't much change from the nakago yasurimei "height" and the "height" of the polished steel... You'd probably guess it had a lot more polishes in it. Or at least one more. But this one was already showing core... And short of somehow sectioning a blade to see the relative locations of core and skin any significant polish can potentially expose an unwelcome surprise.

This thread is quite old. Please consider starting a new thread rather than reviving this one, unless your post is really relevant and adds to the topic..

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