Question about rust and choji oil

[jezah81]

To start of with i would like to wish everyone of you a Happy New Year!

Now to my questions. Does choji oil have an expiry date and if so, how long can it be used for?? Secondly, i found a little bit of surface rust on my 30 year old nihonto. I wiped the old oil off with facial tissue and applied uchiko then reoiled it again. I do this once a week and everytime after i train. Would anyone know how and why there is rust forming on my blade baring in mind i dont live near any salt water area. The oil I am using is about 3 years old. Could this be the problem?

Kind Regards,

[Brian Owens]

While food-grade oils can become rancid, and thus unusable, choji (whether true choji or just mineral oil with some clove oil added) should be fine after three years.

If you clean and oil your blade after every use and you're still getting rust forming between practices, I would suspect that there is moisture trapped in your saya.

You say you don't live near salt water, but do you have high humidity where you live?

[jezah81]

Thanks for your reply Brian. As a matter of fact we do have about 60-80% humidity as it is now summer here in Australia. So, what can i do about this problem if in fact it is the moisture in the saya??


Kind Regards,

[Brian Owens]

So, what can i do about this problem if in fact it is the moisture in the saya??
A couple of things:

You can pour some uncooked rice in the saya to absorb the excess moisture (just be sure to dump it out before your next practice, or you'll be very embarrassed ;) );

You can put some small bags of dessicant in it (I don't know where to get those, but they often are put in with electronic goods for packing);

You could use a hair dryer to blow hot air into the mouth of your saya (but don't overdo it, or it'll get too dry and possibly shrink/crack).

Despite all the rain we get, Seattle isn't really a high humidity environment, so I don't have much experience. Maybe some of the folks from other parts of the world can post better suggestions.

[Kim Taylor]

The salt is coming from you, not the sea. ;-) Sweat is pretty salty, and can also be very acidic.

Rust can dive deep into a blade, especially if it's tamahagane, and there's a line of rust-prone steel, you can get it diving right into the blade before you realize it's there.

Lots of uchiko which will abrade the rust off.

Another less well known item is "sword cleaning water" which is made traditionally by dripping water through wood ash. Now for the chemists out there that's lye, which is potassium hydroxide.

This basic water helps clean off fats, oils and neutralizes the acid. Potassium hydroxide doesn't leave as big a residue as sodium hydroxide so don't use Draino!

And don't use a high concentration of base if you plan on making this stuff yourself! A small amount of KOH will make plain water VERY basic since there's no buffering capacity... you only need enough base to neutralize the acid. Then you clean it off and dry it well and oil the bejeepers out of it.

Sword polishers use washing soda (sodium carbonate) which is also strongly basic to keep the blades from rusting while they're working on them.

So, always always use uchiko or sword water to clean off the bits of skin, oil and sweat from your skin. Don't just oil the blade like you do an iaito since the oil can just seal the sweat down onto the blade (oil and water don't mix remember), clean off the sweat, then oil.

And yes, I've got pits all down the mune of my shinken even though I know all this. It doesn't take long.

Kim Taylor
SDKsupplies.com

[Ken-Hawaii]

I agree with Kim that any salt comes from your body, rather than the ocean or sea. I live right across the street from the Pacific Ocean, & my collection of knives, swords, shinken, & nihonto have never had any problem with salt damage.

I do keep the longer blades in a vault with an electrical dehumidifier.

[Brian Owens]

...Sword polishers use washing soda (sodium carbonate) which is also strongly basic to keep the blades from rusting while they're working on them.
That's in interesting bit of trivia that I never knew.

I've spent many hours watching Token Kono polishing blades, and I noticed that during certain stages the water had a slightly milky look, but never thought to ask him if he'd put something in the water.