Nakago Colouration

[James]

Hey Guys,

 

Just recently I picked up this sword and I inspected the nakago to find this colouration on both sides, just below the ha-machi area. I complained to the seller who insists that it is not at all a negative feature of the blade, and who in fact says it adds character to the blade.

I've my own thoughts about what this is, but to make this discussion unbiased, I'd like to hear the thoughts of others before sharing my own.

 

Please also include your thoughts as to whether this would affect the value of the sword.

 

Here are the photos:

 

[pcfarrar]

It's definitely a negative. Heat has been used, maybe saiha?

[george trotter]

This is the second sword this week that I have seen with this heat treatment...the other was an o-suriage blade in gunto fittings...either shortened in Showa era, or a copy. I would be concerned at such a feature and would hesitate to buy...but perhaps it is not uncommon when associated with shortening and "detempering" the hamon after the machi okuri; can some experienced NMB members give comment on this?

regards,

George.

[sanjuro]

Just an initial impression...............The rainbow effect is a result of heat being applied to the area immediately below the colouration. A naked flame will always produce this when applied to steel which is not then brought to red heat.

Given that the habaki on this sword appears to be an ill fit, and the line of nakago discolouration is quite sharply defined on its upper edge where the blue colour indicates where the greatest heat was applied, The uncoloured steel above that line was therefore shielded from the heat source. Then I might suggest that the original habaki may have been removed by heating (Collapsed or siezed on the blade).

 

Does the habaki moto appear to have been moved at all?

 

I hesitated in adding this, but if the seller of this sword is representing it in the way you have indicated, then I would think twice about dealing with him. He is either a fool or he is dishonest. There is nothing good about this feature, and the only thing it adds to the blade is extreme doubt.

[estcrh]

Just an initial impression...............The rainbow effect is a result of heat being applied to the area immediately below the colouration. A naked flame will always produce this when applied to steel which is not then brought to red heat.

Given that the habaki on this sword appears to be an ill fit, and the line of nakago discolouration is quite sharply defined on its upper edge where the blue colour indicates where the greatest heat was applied, The uncoloured steel above that line was therefore shielded from the heat source. Then I might suggest that the original habaki may have been removed by heating (Collapsed or siezed on the blade).

 

Does the habaki moto appear to have been moved at all?

I have used heat to loosen old plumbing parts that were stuck together so thats a very good explanation, is heat ever used to re-patina the nakago?

[sanjuro]

Excuse my use of the language.... but in answer to your question. Not on my bloody swords it isnt!

That said, there is a whole range of ways to fiddle with patination and I dont doubt that heat may be one of them. I wouldnt think though that anyone wishing to repatinate using any method involving heat would leave so obvious an indication behind. The discolouration is fairly easily removed after all.

 

One wonders if this sword is perhaps a gendaito?

[Veli]

I agree with Keith's analysis.

 

James, are you able to remove the habaki? If someone has applied intense heat to loosen the old habaki, he might have inflicted thermal damage also above the old habaki, in other words, there might be identical discoloration under the present habaki. That would be a serious flaw...

 

Veli

[James]

I agree with Keith's analysis.

 

James, are you able to remove the habaki? If someone has applied intense heat to loosen the old habaki, he might have inflicted thermal damage also above the old habaki, in other words, there might be identical discoloration under the present habaki. That would be a serious flaw...

 

Veli

 

Hi Veli, yes I can remove the habaki. The ha machi is almost non-existant. The blade is o-suriage and machi okuri in my opinion. I believe it is most likely Shinto.

Definately not gendaito.

[John A Stuart]

It would be nice to see an overall pic of this sword. I am curious as to how and who did this alteration. That is one mad wide hamon. John

[drbvac]

I am not crazy about the narrowing between the nakago and the hamachi in the last picture and could the heat have been applied to re-straighten it after it was welded on ? - looks really weird - maybe an artifact from the flash

[Brian]

The blade is machi-okuri, and the heat might have been added to make reshaping the machi easier.

 

Brian

[sanjuro]

Its pure speculation I know, but the banded gradiation in the discolouration which is in fact a heat signature, indicates that the area did not reach red heat.

It would have been necessary for the whole area to have reached red heat in order for either reshaping of the machi or for the straightening of the nakago. There is also no other indication of the nakago being replaced or otherwise tampered with except in a very amatuerish way possibly with an inadequate file, to reposition the hamachi /munemachi. I think in this instance though we may contemplate the extremely sinister, in fact we are simply seeing a less than adequate attempt at moving the machi forward. An attempt perhaps that resulted in the jamming of the habaki on the blade. The heat band being the result of the removal of the jammed habaki.

 

Its fascinating trying to put this together though isnt it?

[Veli]

This is a nice table for estimating the temperature history!

 

http://www.anvilfire.com/FAQ-article.ph ... ilfire.com

 

Veli

[Lee Bray]

Keith, I like your idea but surely the thermal conductivity of copper would not create such a sharp transition?

The habaki would need to be a fantastic insulator to create that transition line.

 

It looks like someone has been trying to draw temper on the tang for whatever reason.

I think we can speculate all day long about why but at the end of the day, a decent smith would not have left the nakago looking like that so it's probably a hack job and should be treated with suspicion.

[sanjuro]

Lee

 

I actually thought about that believe it or not! The copper however would have heated up very quickly, more quickly than the steel of the nakago. If the habaki was jammed on, the solder at the seam would have liquified and the habaki sprung apart long before the steel reached a heat great enough to damage the temper in the steel.

As you say however, we speculate to no avail. The evidence of a botched job is before us and the circumstances of it are academic. The question is.. can it be rectified?

[Lee Bray]

That IS the relevant question and I'd say cosmetically, yes, with polishing. However, the blue colouration evidences that the heat applied to the nakago has been sufficient to alter the heat treat in that area.

So then that begs the question, is the heat treat/sword safe?

If the HT is altered, and recently, how collectible is it?

Probably not very, in my opinion.

 

About the temperature needed to change the temper in the steel and your comment about the solder joint melting first.

I honestly don't think that's the case although I could be wrong. I've softened steel just by the heat transferred from grinding a blade(non nihonto).

No colour in the steel at all, just too hot to touch.

 

I'm thinking the sharp transition line is from possible immersion in water of the whole blade, with heat being applied to the nakago for Keith's stuck habaki suggestion or for machi okuri.