rusty old nakago....

[undermilkwood]

I don't want to get a reputation on the forum for asking irrelevant questions but I have no one else to ask......

 

When it comes to old koto and shinto blades where the rust has taken that fine (almost) black patination, is there any risk that the rust might weaken the metal to the point where the nakago just snaps off or is in danger of snapping off?

 

I'm interested to know how this rust differs from your common all garden rust.

 

Thanks again for your eternal patience with us curious novices.

 

All the best, Joe

[remzy]

Technicaly, yes and no.

But in practice, a loving nihonto-phile will always handle the nihontos under his guard with much care, so there is actualy very very limited chance of the nakago snaping while admiring it or reoiling it.

 

I think that the dark rust (patina) stop the active rust development and serve as a protective coast against red rust that is damaging to the steel.

[undermilkwood]

Thanks remzy :D

 

I wasn't talking about swinging em around, but in the normal course of handling

do you know what exactly happens for the metal to age in this way? I've never seen it anywhere else.

[Walter]

I think, it's all depends from the steel itself.

From centuries, since Hattie’s discovered the iron, many smiths from the different regions of the World tried to find the best possible material for the edged weapon they forged.

Obviously, so far the Japanese sword smiths are the best on this field.

 

I collect the swords and daggers from many countries and always just out-of-curiosity take a look on the tangs and other parts very carefully.

Just can say that all well maintained swords, sabers, daggers, stilettos... etc... doesn't matter where they came from and how old they are have some dark, oily looking rust/patina on the tangs.

I'd agree with Remzy:

that the dark rust (patina) stop the active rust development and serve as a protective coast against red rust that is damaging to the steel.

BTW - very interesting subject and maybe someone more familiar with metallurgy could add more professional point of view.

[John A Stuart]

Hi Guys, Rusting of iron or the iron within carbon steel can only occur in the presence of water, fini, thats it. It is an electrochemical process and requires an electrolyte, water. What is produced is ferric oxide (iron III oxide) Fe2O3. There is an hydrated form and an anhydrous form of this oxide. The hydrated form Fe2O3.xH2O is the red powdery rust we all hate and are forever trying to get rid of. The anhydrous form is blackish in colour and is the form we want to keep. It is insoluable and when nicely patinated forms a barrier to the underlying metal from further rusting by air and water. The red rust is porous BTW and promotes further rusting from an humid atmosphere. John

[undermilkwood]

Ok so it's a form of passivation. Thanks for that John , so if well maintained there is no real danger to the blade. Is there a kantei term for this type (ii) rust, just as an after thought, used when determining the age of the piece?

 

All the best

 

Joe

[Guest reinhard]

Many old Tachi were cut down later to a more wearable length during later 16th and early 17th century. The patination of the new tang started again hundreds of years after their manufacture. Furthermore tangs of only slightly shortened swords were sometimes completely worked over. Paul Martin explained the details on this forum. Therefore the state/color of patination can only be a hint but is no safe pointer. It also depends on factors unknown to later owners like: climate, outdoor use, sword-care and so on. If there is a terminology, it is not particularly mentionned in sword-appreciation.

 

reinhard

[remzy]

Reinhard hit the nail on the head , ive seen shinshinto swords with rustier nakagos than koto blades' nakagos and vice versa, it all depends.

[undermilkwood]

Thanks again for the information, it helps fill in the voids. :D

 

All the best

 

Joe