Black stain spreading on keris during vinegar cleaning

Anthony G. · 10th March 2020, 04:15 PM

Quote:

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 · 10th March 2020, 05:04 PM

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 · 10th March 2020, 09:26 PM

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. · 11th March 2020, 05:10 AM

Quote:

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 · 11th March 2020, 06:27 AM

Quote:

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 · 11th March 2020, 07:00 AM

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.

10th March 2020, 05:04 PM	#2
apolaki Member Join Date: Oct 2008 Posts: 160	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).

10th March 2020, 09:26 PM	#3
A. G. Maisey Member Join Date: May 2006 Posts: 7,015	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.

11th March 2020, 07:00 AM	#6
A. G. Maisey Member Join Date: May 2006 Posts: 7,015	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.