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How to remove fire scale (if at all)?


Marius

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Dear All,

 

I have a tsuba, described by Sasano as Kyo-sukashi from middle Muromachi. I don't think mine is that old, although it matches the Sasano example in almost every respect. Nevertheless, it is a nice tsuba, deserving to be rstored. While I have had good experience with removing loose rust (washing in soap water, drying, working with pieces of bone, going slowly and methodically), I have no idea what to do with fire-scale. Any ideas?

 

Thank you :-)

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I know that blade smiths use vinegar to loosen up fire scale on their blades after forging. Soak overnight and brush the scale off with a wire brush.

Doesn't sound a particularly pleasant way of dealing with an antique tsuba though so please don't take that as a recommendation.

I have no idea what the vinegar will do with the old patina but cetainly imagine the brush will do it no favours.

 

So, I figure vinegar may be helpful, but will leave it for the knowledgeable guys to say whether I'm an idiot for even mentioning it.

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I know that blade smiths use vinegar to loosen up fire scale on their blades after forging. Soak overnight and brush the scale off with a wire brush.

Doesn't sound a particularly pleasant way of dealing with an antique tsuba though so please don't take that as a recommendation.

I have no idea what the vinegar will do with the old patina but cetainly imagine the brush will do it no favours.

 

So, I figure vinegar may be helpful, but will leave it for the knowledgeable guys to say whether I'm an idiot for even mentioning it.

 

Hi Lee,

 

Thanks for the advice, I appreciate it. But wire brush? Never. That would boil down to having this tsuba destroyed. What is legitimate for a newly made sword, is ceratinly not for an old tsuba.

 

Anyhow, nice to learn something new (the vinegar trick, that is)

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I really think if you have fire scale (and it certainly looks that way) then your tsuba is a goner. You'll wind doing severe damage to an already severely damaged surface. Also, I would be anything that tsuba would paper to Shoami, not Kyo.

Hi Rich,

 

thanks a lot for your input. I believe that in a later edition of Sasano's book the attribution is in fact to Ko-shoami. I will certainly not touch that tsuba, if there is no non-invasive way to get rid of the scale. I would rather keep it as it is and not do any more damage to it.

 

It is a goner, for sure, but at least I can enjoy the shape and the fact that it may be a Muromachi tsuba. I am deluding myself, though, as this motif has certainly been copied until the 19th century, has it not?

 

BTW, the reason why I am asking is that in the Haynes catalogues some tsuba are described like this: "some fire scale, but the tsuba could be restored" or something along these lines... So that was humbug, then? No way to rescue the tsuba?

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Fire scale is a form of iron oxide. As the name suggests it forms, rapidly, when iron or steel is heated. Typically to at least incandescent heat, ie; glowing.

 

The layer is in fact harder than the underlying steel as well as being very brittle. The thickness of the scale depends on the length of time the steel was held at high heat, and the amount of oxygen available to convert the iron to it's oxide.

 

If there is a layer of fire scale on a tsuba it then is clear that any trace of the original patina is now long gone.

 

In my opinion there is therefore no reason to accept the fire scale as the default finish at all. It is in fact possible to remove all trace of the scale without doing any further damage to the underlying material. In fact that would in many ways replicate the second to last step the original maker would have carried out prior to developing his protective patina.

 

Once the scale is safely removed,( and I won't be telling the whole world how to go about this as I hate to be the cause of yet another area of sword related DIY :shock: :roll:) it is possible to develop a perfectly reasonable replacement patina, which, while probably not an exact match for the original, would not be all that evident to the vast majority of collectors.

 

Regards,

 

Ford

 

p.s. Repair to damaged tsuba like this was, I believe, not an uncommon procedure in the Edo period. There would be no reason to discard a perfectly serviceable tsuba, particularly one with some age, just because the patina was damaged.

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Excellent points Ford. There's often talk about the masses of retempered blades in existence which supports a rational conclusion that there are as many (if not many more) tsuba that also suffered from these events. I would suspect that quite a few of those we see today have been restored, the degree of skill applied determining any detectable features of the restoration. Would you agree with this? If so, allow me to elaborate with a follow up question;

 

Swords that have been retempered obviously can exhibit visual indications of the process. We are taught to look for these features as a matter of judgment (and prudence), when examining swords. Granted, tsuba are not restored under the same processes (i.e. polishing), yet the nakago of swords is something I would see sharing similar considerations for restoration that tsuba would. So, in your experience, is there perhaps any "layman's" list of things to look for in iron tsuba that could help our members detect prior damage and/or restoration? I don't think anything like this has ever been covered here, and aside from the obvious such as, growing red powdery rust or flakes of scale falling off, perhaps there are other things less obvious we should look for. Comments?

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Hi Ted,

 

First off I honestly don't think the average iron tsuba that had been repatinated by a competent artisan sometime in the Edo period will look all that different to what an untouched guard would look like. I think that, as you suggest, the practice was probably more common than we would like to think.

 

We're used to all sorts of defining characteristics for specific schools in terms of iron quality, hardness ( how that is measured with fingers I can't imagine :roll: ) texture and colour etc. But the reality is that these traits are really the gold standard that we can expect of the finest, text book examples. That leaves a huge number of guards that for all sorts of reasons deviate from the classic examples. To be honest I think that the issue of colour is most problematic given how subjective it is.

 

So what I'm suggesting is that, for example, a classic Ko-Owari guard that lost it's original patina around 1600 could quite feasibly have been repatinated 200 years later by a skilled artist and we'd not necessarily be able to tell. There will have passed enough time to develop the required "crud" in the piercings and it will have had sufficient time to mellow and acquire a "gleam of age". The point being; we really can't judge the age of patinated iron visually and there is no definitive nor reliable dating method for metal.

 

Much is made of the time needed for various corrosion products to develop but there again it all depends on the environment the object was kept in. 2000 year old Iron artefacts found in the middle east are generally in far better condition than the average 400 year old European sword.

 

My view would be that if it looks right and is beautiful then we can leave it at that because I think we'll never really be in a position to be absolutely certain. We come down to the consensus of educated and experienced opinion.

 

Sorry I can't provide a litmus test :dunno:

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I have had success getting rid of fire scale by soaking the tsuba in oil over night and then going over it with a bone prick and doing it over again a few times if need be, took me some time, but the fire scale is now gone.

 

 

James, what kind of oil? And I presume that you have had the tsuba repatinated?

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