Black stain spreading on keris during vinegar cleaning
 

I have a really perplexing dilemma. I gave this keris I posted a long time ago a bath recently in diluted vinegar (originally 5% acidity), but I poured and mixed 2+ cups of water.

http://vikingsword.com/vb/showthread.php?t=21446

I let it sit in the bath for a couple days (taking it out to scrub rust off and rinse before resubmerging in the same bath, what happened is black stains began to form on parts of the keris.

The stain can not be scrubbed off. By scrubbing, it only stains the toothbrush and water a dark black like paint. To make things worse, the black stain emits a strong chemical oder I can only describe as similar to burning tires! It is a noxious fume that permeates the entire bathroom with a horrible stench :(

The exact same thing happened to a moro kris I attempted to clean with diluted vinegar, and it turned out to ruin that moro kris in the end.

Essentially with both the Indonesian keris and Moro kris developed the black stains. Furthermore, the blackened parts of both blades look like they are corroded the blade as though they were burnt in a fire.

Here are some photos of the black staining of the keris that is spreading. What could it be?

I have no real clues but just submit my personal comments and opinion:
. The blade cleaning is not complete (remaining rust spots) probably because the vinegar is too diluted. I am using undiluted vinegar at 8-10% and I cover the vertical container for avoiding evaporation of the volatile acetic acid. The cleaning procedure usually lasts 24 h only with 2 intermediate brushings.
. From the pics, the black spots look like exposed and corroded steel or iron. As said by Alan in the last thread, the blade has pamor sanak.
. Is the bad smell like rotten eggs? In this case it would be hydrogen sulphide caused by the presence of iron sulphide in the metal and attacked by the weak acid.
Regards

Apolaki to clean the blade you can also use acid citric . You can put the blade inside 1 lt water with three little spoons of acid citric (white dust). Little by little the rust goes away. I used this way in the past with good exit.

Apolaki, I believe that the black you can see is the steel core that has been hardened. The small specks in the body of the blade could be where the outside layers have worn, or, as Jean has suggested, maybe some steel is in the mix of the outside layers, but the big black areas at the point & edges are steel core.

As to cleaning with vinegar I am not nearly as scientific as either Jean or Marco. I buy ordinary white household vinegar, I have not the slightest idea of its acidity, I never dilute it. I simply wash the blade with detergent to get rid of any grease, and soak it in the vinegar. I inspect it once or twice a day and brush it as well as pick off the rust with a sharp tool, then I put it back into the vinegar. It might take me a week or more before I'm satisfied that it is clean.

Jean has my utmost admiration if he can get a truly dirty blade clean in 24 hours with only 2 brushings. Incredible! You're a better man I am Jean.

my way to clean blades (with rust difficult to remove with other easier systems) is only empirical and rather fast.... sorry for my bad english

Nitric acid is faster Marco.

But jokes aside, citric acid works well, I've used that too, and a lot of people in Indonesia currently use citric. In fact anything acidic will clean a blade, its just that I prefer vinegar because it is cheap, easy, consistent.

But if I could still get decent pineapple juice, I'd still be using that.

I used home vinegar before and soak for a day during weekend. The old balinese keris has a part on the bilah which is almost what you have described. I think it is the steel core.

Thanks all, so the steel core is reactive poorly to the vinegar. Is the damage irreparable?

I have now taken the keris out of the vinegar bath and placed it in a bicarbonate and water bath (or as we say in the States, baking soda and water).

Apolaki, the steel core is not reacting poorly, and it does not need any sort of repair:- it is reacting exactly as it is supposed to react and it is an indication that the blade has been heat treated.

Thanks for info. I knew that keris is heat treated now. Cheers

The reason I thought the keris is now damaged is due to the edge. It used to be a straight edge throughout, but now the edges particularly where the black stain is has a serrated/corroded edge look as I have circled in red.

Also the black stain is not removable so it leaves a un-uniform look to the keris.

I am interested to learn more about heat-treated keris blades and how/why vinegar effects it in this manner. Is there any literature you can link me to?

Were the pamor keris I cleaned prior with vinegar all non-heat treated/ did they not have steel?

Also, what is the point of heat treating a keris?

Thanks!

Older keris very often have uneven edges, if it troubles you you can even up the edges by filing. Personally, I would not bother dressing the edges of an old blade unless the edges were very severely eroded and/or the blade was of very high quality. The little bit of erosion that you have drawn our attention to is nothing. It is normal, just accept it.

Apolaki, this is a keris. Everything I can see about this keris is totally normal for a keris of this age and quality. Yes, the edges are uneven, yes, the colour is uneven. This is exactly what we expect with a keris like this. There is nothing wrong with it, it is normal.

I cannot refer you to any published works that can explain why heat-treated steel goes black. I guess it is simply because the steel contains carbon, the iron does not, when the steel is heated and then suddenly cooled the carbon at the surface goes through some sort of change. An engineer can probably explain the reasons, I cannot.

As to why you did not see this change in colour in other keris you have cleaned, there could be a number of reasons. Maybe they had not been heat treated, or if they were old blades, maybe the blade had been annealed and the steel had become soft, maybe the blade did not have a steel edge or core, maybe it did have a steel core, but the core projected around the edge by only a small amount and any colour change would be difficult to see, maybe only the tip of the blade was heat treated. Lots of "maybes" and a different maybe can apply to different kerises.

If you do not like the look of the blade as it is, you could always repolish it and then use cold blue that is used for firearms repair to give it a deep blue colour.

Hello Apolaki,

I'm still at a loss about the stench you report; rotten-egg smell is certainly not unheard of though. There is a reason why most of us do these things outside, in a shed or in some other well-ventilated area... ;)

I'm also pretty pretty sure anyone possibly living with you wouldn't appreciate any fermenting pineapple juice with fungus floating on top. :eek: :rolleyes: :D

Having said that, keris Jawa blades can be especially porous and whatever happens to hide inside those crevices may differ quite a bit and possibly contribute to unexpected "features" as well.


The general rule for traditional/historic iron/steel: the greater the amount of carbon, the more susceptible they are to corrosion (i.e. rusting away). If any given steel alloy has been hardened, it corrodes even quicker than unhardened. For more details you can consult metallurgical text books but as Alan notes, this is not really needed for basic cleaning efforts.

Any smooth-looking edges with enough patina on them so that you can't see the bare steel anymore is likely to have patches consisting of rust rather than steel. When you start cleaning, the rust will fall off and these patches will look like in the pics you show (or worse). For keris Jawa this appearance is culturally accepted nowadays.


Regarding the aesthetics of the final result, I suggest that you're still in the middle of the cleaning phase: It would be good to proceed to remove all rust as Jean already suggested. One usually tries to limit exposure of the blade to any acid and manually scrubbing the blade and individually picking the remaining spots of rust as described by Alan really helps the acid to finish its job quicker.

Once the rust is completely removed (pics with flash can help to detect any remaining rust), you could try to rub a cut lime fruit over the dark areas, if you prefer lesser contrast. I usually do this as a preparation before progressing to warangan.

For pretty much any keris Jawa or keris Bali/Lombok warangan is needed as a final step to bring out the traditional look of the pamor. If you can't do that, it might be worth a try with other etching approaches including the cold blue suggested by Alan. While the exposed steel core will always stay visible (perfectly ok), the main part of the blade should have some pamor to show which would lessen the current B&W contrast.


BTW, that Moro kris is far from ruined! (Unless you haven't shown us his most recent reincarnation...)

As far as I could see, the overall surface wasn't even porous and just needs "a little" touching up with some polishing effort. Needs a bit of tedious work but feasible even for any beginner.

The more experience one gains with restoration, the better one is able to predict the final outcome and the hopefully best strategy to achieve it with the least effort. Most errors or results of less suitable approaches do not tend to have severe consequences and can be remedied with additional efforts. However, it helps to obtain frequent feedback during each project to progress along the learning curve - I'd posit posting pics of the current status of any ongoing projects more frequently!

The more a blade approaches any relict/excavated condition, the more careful one should consider just leaving it alone though. (There is a reason why we tend to speak of "ghost" blades in forum parlor, especially with keris Jawa.)

Regards,
Kai

Kai, I have tried cold blue on a normal contrasting pamor blade but it does not produce acceptable results.

However, on pamor sanak, which is all ferric material, it can produce more or less OK results, and for touch-ups of worn areas on a blade that has contrasting pamor it works really well. I'm talking about very small areas when I mention "touch-ups", areas less than, say, 3mm X 3mm.

What you say about sensitising the blade prior to warangan by rubbing a cut lime over it is better achieved by brushing with strained juice from Tahitian lime, freshly squeezed.

Alan or anyone else - might you be able to show have a good example of a darkened pamor sanak blade, or a pamor sanak blade which has had cold blue applied to it such that it produces an "ok result"?

I cannot. Sorry.

How do you indicate that this is pamor sanak? I see the word mentioned several times. From when I cleaned the blade, I could not find any distinct contrasting patterns in the blade.

"sanak" means "related", a relative, or a relation.

"Pamor Sanak" is "related pamor"

Related to what?

The rest of the blade, in other words the pamor is ferric material, usually of various types, blended together. It is not usual for pamor made exclusively of ferric material to provide contrast, but if white iron (high phosphorus iron) is used you will get a low key contrast.

If a blade does not have an obvious pamor (e.g. using ferric and non-ferric materials such that obvious contrasts in the damascene pattern can be seen), how often is it the case that it can be called "pamor sanak"?

Would this be almost the same as asking this question:

Were keris or other tosan aji from what is now Indonesia ever made using a single material, such that there can be no pamor to speak of?

We usually classify something as pamor sanak if we can see the weld lines but there is no contrast, in other words, the outside layers have been made by welding together an assortment of various irons.

Yes, there are blades from various places that give the appearance of having been made from only the one type of material.

During the 1980's in Solo the elite of ahli keris that I came in contact with seemed to hold the opinion that in Sultan Agung's time, and also before and after, keris that were made specifically as weapons were made without contrasting pamor, whilst keris that were made with pamor and/or naga and other carved motifs were made for talismanic or social reasons.

Re: Vinegar, C6H8O7, NaCl and H2O2.
 

For what little it may be worth, I've done a few rust removal experiments on planer blades (from lumber mills), neglected and abused Mora knives of laminated steel construction, "load binders", and hard-to-come-by threaded fasteners using either undiluted acetic acid from Canadian or Filipino producers, undiluted Peruvian lemon juice, or an ad hoc mixture of both. For blades, I'll wrap in paper towel, apply liquid to saturate, then wrap in common, food grade plastic wrap or a similar shipping grade product. The result after unwrapping 12-96 hours later is always a strong odour which I'd describe as mouth-watering in a Limburger cheese sort of way. Provided that care has been taken to remove all oil and/or grease from the steel treated in such a way, in most cases, the rust will have disappeared, and the steel will be quite black, and vigorous rubbing with nothing more abrasive than a paper towel or a stick of (soft, not hard) softwood is needed to remove this blackening completely. Faster results might possibly be achieved using a toothbrush, perhaps in combination with toothpaste. This last mentioned method works on silver plate and coinage (though I'd discourage it), but I've never tried it on steel.
I've read of a method used at one time in Japan to cause a durable layer of glossy, black protective oxide to form on chisels and axe heads by first soaking in a solution of water and kosher salt until fully coated in rust, and then boiling the rusty tool in hydrogen peroxide to bring about the conversion of the rust to the protective black oxide. I've yet to try this method, but have considered it for "gardening-variety" machete, parang and golok, and as a possible alternative to traditional warangan treatment for keris due to arsenic being unavailable where I'm living. If anyone has any knowledge of this method, any input would be appreciated.

Hi Marco,

I don't access to acid citric. Where can you get that?

Also, can I use concentrated lemon juice and water? If so, what is the recommended ratio?

Hi Apolaki
I have always easily found citric acid in the pharmacy (here in Italy). Citric acid resembles as white sugar and I used this acid only with blades where the rust was very difficult to take away as old rust inside the deep of the blade's structures. When you will have the citric acid you must put some spoons of this dust into water and you must put all the blade inside this water for one day or more or less (it depends how many acid you put in the water) and , for exemple, every hour, you have to see the the blades to control the process.
Western lemon juice, in my experience, works well together bicarbonate-soda if I want to take away old warangan from the blade ...and to clean the blade before to put a new warangan

Marco what ratio of lemon juice to bicarbonate soda are you using? Are you making a paste and scrubbing with a tooth brush?

yes... I used exactly this way

Great! What is the ratio you use?

A word to the wise:

A great regret of mine is opting to use citric acid as opposed to regular white cooking vinegar, on one of my old blades.

It was the first time for me cleaning any blade.

Firstly I put too much citric acid in and it flaked some of the steel off the blade.
It was already in quite a fragile state due to its purported age, and the concentration of citric acid was far too harsh.

For this reason I will always opt to use cooking vinegar and father time.

Jaga, I understand where you're coming from with this, and I'm of the same opinion, but only because I've used vinegar for years & years now and never had even the hint of any sort of negative result.

However, if I was new to the game I'd be looking at everything, including Coca-Cola and tomato juice. It is the nature of human kind that most people like to learn by their own mistakes.

That said, Marco used a very short term hands-on method with his citric acid. People in Solo have been using citric for years, and citric acid is what a lot of people in Solo use. Bi-carb used as a cleaner is great stuff to remove stains from tea cups and coffee cups. Bi-carb is really wonderful stuff for lots of things.

Lemon juice is in fact pretty high in citric acid to begin with. Used as a paste of bi-carb with a toothbrush I reckon it would be pretty effective. But even so, I'll stay with vinegar because of my experience with its impeccable record and because it is so easy and non-time consuming to use.

Actually, the acid in vinegar is acetic acid, and that is pretty strong stuff, but there is usually only about 5% or 6% in household white vinegar, the rest is water.

Personally, I would encourage all beginners to try everything that they can think of and to learn by their own mistakes:- there is nothing as sobering as destroying something that cost you money, by failing to learn from the mistakes of others.

The black stain has spread throughout the blade, it is like infected the blade.

Nothing is infected Apo, I'm looking at normal here.

Pick off the hard rust with a small, sharp tool.

Get some coarse steel wool and some powder sink cleaner, give it a good scrub under running water.

Dry it and put it back in the vinegar.

No fluid is magic, it is just a substance that helps you to get the job done. If I look at the pics of this blade I can still see a lot of what appears to be rust. I suggest you pick this off, scrub it off, as I have advised above.

When the thing is clean, dry it thoroughly and then either stain it or spray with WD40.