Acid job? What remedy?

[Marius]

Dear All,

 

I have recently purchased a very tired koto ko-wakizashi. I could not resist, I like the shape of it, looks like Soshu, and maybe it is the next sleeping Masamune The hamon has survived and it is nie deki, I believe. However, the hamon is dark and looks like it has been "brought out" with acid?.

 

Anyway I can remedy this, without another polish, which this piece would surely not survive?

 

Pics are attched. Thanks for your help, I appreciate it

 

 

 

 

[Guest nickn]

lots and lots of uchiko work if fact use uchiko until the black from the acid doesnt appear on the tissue

[remzy]

What Nick said, but lightly oil every two or three wiping of uchiko to lubricate and help dirt get off, perhaps it will take some off the stain off but i doubt it will get it all off as acid job usualy mess the steel internatly.

[Guest nickn]

i have used t-cut before on acid polish swords with good results

now before you all condem me think nugui iron oxide in suspension t-cut aluminium oxide in suspension

so it will not scratch steel and i am only suggesting using it on acid polished swords not proper art polished ones uchiko then t-cut repeat until the black from the acid does not show on the tissue i had a very rough emura polished by JB ,his commercial polish, and spent several weeks with uchiko before the hada started appearing . i do not believe acid continues to eat into a sword that is not how acid works its just not chemistry

[Marius]

Dear All,

 

thanks for all the good advice. I have started with uchiko, as my I have no ready access to nugui and would have to import it from Japan. A lot of brown dirt comes off and the hamon looks already better. I will uchiko this sword on a daily basis for a week or two and I shall see what comes out, but I am sure that most of this disastrous acid "polishing" will be removed. I will let you know in about a week :-)

[Kevin]

i do not believe acid continues to eat into a sword that is not how acid works its just not chemistry

 

Hmm! It depends on what they've been using. Some folks use nitric acid, so you'd be OK. Others, however have been known to use either hydrochloric or iron III chloride. If you use hydrochloric acid you'll get iron III chloride formed. Iron III chloride would be, I would think, a serious problem if it got in the grain. Firstly, it is a fairly strong Lewis acid and it is used for etching circuit boards. It's nicely deliquescent, so it attracts moisture, and the anhydrous form gives off hydrogen chloride.

 

The problem isn't necessarily acid eating away the metal. The problem is the attraction of water, plus chloride ions, plus acidic oxygen rich environment, plus iron equals accelerated rusting. Chloride corrosion of iron and steel is well-known - think of the accelerated corrosion of reinforcing bars in concrete bridges where road salt has got in, leading to iron III chloride formation. It is a major problem stopping it once it has got in - it has been likened to a cancer of reinforced concrete. You get a similar extravagant rusting if you leave iron or steel in oxygenated sea water. Similarly, it only needs a little iron III chloride to be lurking in a bit of open grain for it to start causing problems which, if untended, could seriously damage the sword.

 

I'd be tempted to wash it very thoroughly in a sodium carbonate solution several times (watch to see if any fizzing appears anywhere), then throughly dry before polishing and oiling.

 

OK, not the recommended treatment for a nihonto, but possibly a good precaution for one that's had an acid 'polish'.

 

NB: Thought I'd add that the above effect is effectively a battery, with the iron III chloride acting as an electrolyte, and the return path being through the sword. The reaction goes on for as long as there is enough metal to conduct electrons. Hydrochloric acid or iron III chloride (formed by the former) would be extremely bad news for a nihonto, especially if the grain allowed it to get deep into small spaces in the metal. The only way to deal with it would be to neutralise the Lewis acid, otherwise in a few years you'll just have an interesting pile of hydrated rust.

 

Kevin

[Guest nickn]

use t-cut i only mentioned nugui to point out that t-cut is milder ,aluminium oxide, then nugui , iron oxide, which is used to darken the ji and not to clean/polish

[Marius]

Again, many thanks for all that valuable input

 

I have had an extensive uchiko session yesterday and it has worked! :D The worst stuff from the acid "polish" has come off, apperently. The yakiba is now much brighter, and I can also see more of the hamon when hoding the blade towards a source of light. I will continue with uchiko for a few days, I don't think I can do this sword much harm this way.

 

I have always avoided uchiko, so this is the first time I am grateful that the Japanese have invented it :lol: