Black stain spreading on keris during vinegar cleaning

[apolaki]

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?

[Jean]

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

[Marcokeris]

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.

[A. G. Maisey]

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.

[Marcokeris]

Originally Posted by A. G. Maisey

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

[A. G. Maisey]

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.

[apolaki]

Originally Posted by Marcokeris

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.

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?

[Marcokeris]

Originally Posted by apolaki

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

[Interested Party]

Originally Posted by Marcokeris

Hi Apolaki
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?

[Anthony G.]

Originally Posted by apolaki

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 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.

[apolaki]

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).

[A. G. Maisey]

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.

[Anthony G.]

Originally Posted by A. G. Maisey

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

[apolaki]

Originally Posted by A. G. Maisey

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.

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!

[A. G. Maisey]

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.

[kai]

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.

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.

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.

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

[A. G. Maisey]

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.

[jagabuwana]

Originally Posted by A. G. Maisey

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.

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"?

[A. G. Maisey]

I cannot. Sorry.

[apolaki]

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.

[A. G. Maisey]

"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.