Best way to deal with rust spots

[Emil]

Upon closer examination of a katana I recently gifted my father, I see small dots along the blade. 2 months ago, when it first arrived with at my brother’s, he sent me pictures of it. I saw the small grey dots but assumed it was just dust. So it doesn't appear to have worsened in the last two months.

 

Mostly they the spots go unnoticed, but I can see that they have a yellowish tone if I look really close in some light conditions.

 

I advised my dad to keep it well oiled at all times. However, every time it's pulled from the shirasaya there are small wooden flakes on the blade. It's probably been stored in this shirasaya for many years already, judging from the aged look of it.

 

What is my best course of action to prevent further oxidation? What would you have done in regards to blade and shirasya?

 

Now that this licensed Showato has left Japan and the torokusho has been returned, there are no guarantees that it will pass inspections and be let inside Japan ever again. Let alone the price of a polish, I'm quite concerned that if left as is, it might get worse?

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[Brian]

Use a wooden toothpick and some oil and see if you can clean those dots. Then keep it wiped and very lightly oiled.

[Emil]

Thanks @Brian, I tried it but without any luck. I think the problem is that the toothpick is larger than rust pits and they felt very sturdy.

[Matsunoki]

Emil, it is very possible that the small dots are the remains of some tiny rust pits that have mostly been removed by the polisher but have now filled up with uchiko powder.

If toothpick is too big try a wooden cocktail stick with very fine sharp point and use gently with great care! Rotating the fine point in the pit might reveal what the white stuff is. Can’t stress enough how careful you need to be …..use high power magnifier but let the oil sit on it for a while before trying. 

[French nihonto]

I think there are many techniques, many of them very good. I had an experience with a rust stain on one of my blades that had been in customs too long. The stain was much bigger than yours. I inhibited one of my microdear with clove oil and rubbed it gently for just over an hour. Using my fingertip to be as precise as possible, after just over an hour and quite a bit of pain in the arm and hand  (I understand the physical difficulty for a polisher who does this sort of thing all day), the rust stain turned into a clove oil stain, and I rubbed gently for at least an hour. The rust stain turned into a small light white stain and the steel was healthy again. And the polish around the stain remained perfect. Very archaic but it worked for me 

[Emil]

Thanks for the advice @French nihonto and @Matsunoki

 

How concerned should I be about the Shirasaya leaving wooden residue on the blade?

 

 

 

 

[French nihonto]

55 minutes ago, Emil said:

How concerned should I be about the Shirasaya leaving wooden residue on the blade?

 

The solution would be to make a new shirasaya. Sometimes an old shirasaya can be quite healthy, but sometimes it's not. Uchigo powder, blocked humidity, wood that is staining. 

[Matsunoki]

4 minutes ago, French nihonto said:

The solution would be to make a new shirasaya.

Having a new shirasaya made for a blade after it has been polished is fraught with danger. The precise process of fitting it to the blade requires much handling and thus scope for scuffs, scratches etc no matter how careful the sayashi is. Usually the s/s is made before polish I think.

Finding small bits of wood on the blade is common especially if the s/s (or saya) has some age but it’s not something I would worry about if it is just the odd very small piece provided the blade is kept oiled and stored in the correct orientation ie edge up.

It’s a tricky decision. Personally I’d just leave it and observe regularly.

[Gakusee]

2 minutes ago, French nihonto said:

The solution would be to make a new shirasaya. Sometimes an old shirasaya can be quite healthy, but sometimes it's not. Uchigo powder, blocked humidity, wood that is staining. 

Not necessary to always make a new one, especially for a showato.
In fact, even with my Kamakura blades I did not have a new shirasaya made after the fresh polish and instead opted for thoroughly cleaning the old shirasaya. No issue whatsoever with the freshly polished blade thereafter. 
 

The old shirasaya can be opened (after all it is only glued with a rice-paste adhesive) and cleaned very throughly. The cleaning process actually is abrasive and removes surface deterioration within. After that is done, it can be easily reassembled. This is all best done by a professional. 
 

Mind you, however, a cleaning process could cost 60-70% of the price of a new shirasaya (if done in Japan) but will be a smaller expense if done in the West (10-15%). The reason is that honoki is still more available in Japan (although even there it is becoming scarcer) and in Japan of course people value their time and you need to send the blade and old shirasaya etc etc. 

 

In short, I think we are overthinking it here and I am not convinced these tiny, barely-visible spots are the artefact of the shirasaya. If the blade is well oiled and well taken care of in appropriate environment, this would not happen. Also these could be tiny “breath/saliva” induced spots too when someone looked at the blade and did not wipe it clean thereafter. 

 

 

[Emil]

17 hours ago, Matsunoki said:

it is very possible that the small dots are the remains of some tiny rust pits that have mostly been removed by the polisher but have now filled up with uchiko powder.

 

I managed to take some close ups with 30x and 60x magnification

 

 

 

 

 

[Emil]

3 hours ago, Matsunoki said:

Finding small bits of wood on the blade is common especially if the s/s (or saya) has some age but it’s not something I would worry about if it is just the odd very small piece provided the blade is kept oiled and stored in the correct orientation ie edge up.

It’s a tricky decision. Personally I’d just leave it and observe regularly.

 

 

It looks like this every now and then when I open it

[Lewis B]

I have the same issue with the Mino senjuin katana I acquired. For me this over application of oil, which gets onto the wood causing it to swell. The reduced clearance and and contact with the edge leads to these wood shards. My other two Koto blades had a minimum film of oil (not visible) and I've yet to encounter the splinters. I would ask Patrice Sabah in France what he would charge to refurbish the shirasaya. 

[O koumori]

Over the years, I've developed the habit of lightly bumping the saya on a padded surface, koiguchi down, to dislodge any stray fibers or particles before re-sheathing the blade. Seems to work well!

 

Dan K.

[Emil]

2 hours ago, Lewis B said:

 For me this over application of oil, which gets onto the wood causing it to swell. The reduced clearance and and contact with the edge leads to these wood shards.

 

I think I'm over oiling the blade, but since there are a few rust spots already I'm afraid to leave it too dry

[Emil]

1 hour ago, O koumori said:

Over the years, I've developed the habit of lightly bumping the saya on a padded surface, koiguchi down, to dislodge any stray fibers or particles before re-sheathing the blade. Seems to work well!

 

Dan K.

 

I'll try that, thanks 👍