The Cleaning of Blades

[A. G. Maisey]

My response to Kai's comments:-

Quote:-
I prefer to work over the blades at least twice daily; I also make sure to thoroughly degrease the blade prior to the acid treatment. If oil shows on the surface, I remove the blade, dry it and degrease again (fittings and crevices can harbor residual oil) - this makes sure that the acid can work on all remaining rust (and, thus, shortening the exposure time).

Agreed, twice daily is better than once daily, and in fact with some blades I will look at them several times during the day if I am able, but for the general run of blades, I usually only rinse off and get rid of freed up rust once a day.
Actually, some deeply corroded blades need to be gone over under magnification and each pit in the blade cleaned mechanically with a needle. I remember one Bali blade that I did like this in order to preserve the original stain. It took me months, half an hour at a time.

The scrubbing part of the process I used to do only with a toothbrush, but these days I use a variety of brushes, depending on the nature of the corrosion, and if necessary I also use steel wool or Scotchbrite pads, or stainless steel pot scrubbers. Probably not a good idea for a beginner to use these more abrasive methods.

Quote:-
This may be true for the keris Jawa culture. OTOH, acetic acid of any notable concentration will eat away iron (and steel even quicker)! If you compare early collected keris from European collections with their "relic" counterparts that have been traditionally "washed" multiple times, I believe it is fair to say that acetic acid (as in coconut "water"/vinegar) does damage keris blades in the long run. The loss of material may be mainly from removing rust which certainly develops quite quickly in a humid tropical climate; however, put some clean steel in vinegar for days and you'll clearly see corrosion. Thus, I suggest to limit the time in any de-rusting fluid as much as possible. (And, of course, the higher the acid concentration, the shorter the exposure time (with checks/cleaning done more often)!

Kai, there is doubt at all that any acid, if the strength is sufficiently great, will eat ferric material, however in my experience fruit juices will have no effect at all up to even months left in the juice, and as for white cooking vinegar, I can say the same up to 3 or 4 weeks.

The erosion noted on old blades is the result of rust that has formed on the blade, the cleaning process has removed the rust and exposed the pitting. The cleaning of anything requires a degree of skill, and cleaning keris blades is no exception. It is not the cleaning process that causes the erosion of the material, it is plain old neglect and the consequent rust.

Your suggestion to put clean steel in vinegar for a few days and note the result indicates to me that your vinegar must be very powerful stuff. The vinegar that I use has no effect on clean ferric material at all, even when the material is left in the vinegar for 2 or 3 weeks.

There is something else that needs to be recognised also:- keris blades and other similar blades only have steel edges, the covering of the blade is iron, or iron + nickelous material. The heat treated steel will certainly react more quickly to both rust causing agents and to acid, this is reason why blade edges sometimes emerge from cleaning in a frayed condition, and the smoothing of these frayed edges is recognised as a part of a cleaning job, but if the rust was not there in the first place, the edges would not have become frayed.


Kai, this last bit of advice that you have given I find both interesting and possibly valuable, my original comment comes first, followed by your comment:-


Quote:

My original comment:-
I've used this method on a wide variety of blades, seems to work well on everything I've tried it with, however, a katar might have small gaps where metal meets metal, and it would not be easy to get residual acid out of those gaps. Occasionally I might use a slurry of bi-carb of soda to kill the acid, then thoroughly rinse off the bi-carb.

Kai's response to my comment:-
With vinegar, this is actually an unnecessary step: The beauty of acetic acid is that it is quite volatile - you easily smell it.

Just heat the blade thoroughly, and any residual water as well as acetic acid is gone! A hairdryer is a pretty safe tool - if you're kinda paranoid (which is a good trait for any conservator!), make sure to heat just above the boiling point (i. e. 100°C). This may be easier in a temp-controlled oven - however, arsenic is also volatile...
(Anyway, ventilate well and don't do this in your collection room!)


The "smell test" might be valid, I don't know, my own sense of smell is not particularly good, and in any case, if I am working with substances that do have a smell I don't notice it after a while. The vinegar that I use has no really noticeable smell at all, certainly none noticeable from a couple of meters away.

What is interesting to me is that heat will get rid of any residual acetic acid.

Why is this so?

I have used vinegar to clean mechanical damascus, and in my experience unless I use a bicarb slurry on the blade prior to the final rinse, there will sometimes be little patches of rust on the blade, bear in mind, this is a smooth polished surface I'm talking about, not a rough surface as with most keris.

Also bear in mind that in my complete cleaning instruction that I posted above, I do recommend heating after drying with a cloth. These days I use a hairdryer, but years ago I often used just direct sunlight for keris, and either an oven with the door open, or a hair dryer for damascus blades. So even after rinse>dry>heat, that rust would sometimes show up, but it never did if I used a bicarb slurry prior to the final rinse.

So my questions Kai are these:-

why does heat remove residual acetic acid?

if heat does remove residual acetic acid, at what level of intensity and duration does this effect begin to occur?

[Jean]

Just few tips about my personal experience for cleaning rusty or encrusted blades. I am using the same procedure as Alan with generally a very good success and only minor differences:
. I am also using household vinegar but try to buy the 10° (10% vol.) brand which is more concentrated/ effective but still does not react with steel or iron as the H+ concentration (the active agent) is too low (or the PH too high).
. I am using a vertical container made of 2 glued PVC pipes (one small one for housing the blade in the bottom part and a flaring adaptor at the top for housing the sorsoran) which I cover for avoiding the evaporation (hence the dilution) of the acetic acid. I am removing and scrubbing the blade twice a day and carefully scrub it with a steel brush or stainless steel scrubber (with Cif detergent) for removing the softened rust.
From experience I never had to spend more than 36 hours for cleaning a blade, even those covered with black rust since 100 years.
I also tested 10% citric acid and 10% oxalic acid solution (products available in drugstores and also weak organic acids) which have the advantange of not being volatile, but I did not find them more effective.
As Alan says, the cleaning of a blade will expose the pitting which was not visible under the rust but the cleaning process does not cause the pitting.
Regards

[Jean]

(deleted)

[Marcokeris]

I normally use citric acid powder (2 teaspoons) added to about 2 liters of water and I leave the blade dipped for a day or two (it depends by the rust) . Then I wash the blade. Then I use sodium bicarbonate with a toothbrush and pass it over the blade. Finally I wash the blade again and dry it with a phone

[David]

Originally Posted by Marcokeris

Finally I wash the blade again and dry it with a phone

These new-fangled phones these days! LOL!

[David]

Hey, i seriously don't want to stop this discussion, but please keep in mind that we already have quite a few threads on washing and/or staining keris. I am always interested in new information on this process, but don't think we need to go over the same old ground again and again so please try to be aware of information that we have already discussed in depth before posting. Thanks!

[A. G. Maisey]

Yes David, I agree, and the old threads cover methods other than acid cleaning.

The major reason I started this new thread is because of two things that Kai mentioned:-

1) that a mild acetic acid can damage steel

2) that there is no need to kill acetic acid residue with bi-carb

Perhaps Kai can give us technical explanations for this, because I have never experienced damage to any blade that I have ever cleaned with vinegar, even though on a couple of occasions I've forgotten I had one soaking, and it got the benefit of 2 or 3 weeks in a vinegar bath.

Similarly, I have seen ferric material react after cleaning with vinegar when I did not use the bicarb slurry before the final rinse. I do not always use bicarb, it is mostly when my experience tells me that I should, or on a return clean when a blade has reacted because I did not use bi-carb the first time.

So now I am waiting for Kai to share his knowledge.

I have only learnt from experience, I have no technical knowledge at all about the things that I use.

But cleaning a blade for the first time might seem like a big thing to somebody new to it, so I believe it is important that those people should get as much guidance as possible.

[Rick]

I have a (new to me) tombak that I have used Picreator Metal De-corroder on to remove the rust which was pretty substantial.
The result shows a noticeable difference in color between the core and the pamor.
I intend to try a strong, hot coffee solution (in lieu of warangan) to try to make that contrast even more apparent.

I'm hesitant to post pictures here as it is not a keris.

[David]

Originally Posted by A. G. Maisey

Yes David, I agree, and the old threads cover methods other than acid cleaning.

The major reason I started this new thread is because of two things that Kai mentioned:-

1) that a mild acetic acid can damage steel

2) that there is no need to kill acetic acid residue with bi-carb

Thanks Alan. Yes, i understood your intentions for open this thread. My note was not directed specifically at you, or anyone else for that matter. It was simply a reminder to everyone that there is no need to spend time and space covering aspects of cleaning that we have already discussed in much detail. New information is always welcome.

[kai]

Hello Alan,

I apologize for my slow reply - thanks for keeping the ball rolling!

why does heat remove residual acetic acid?

if heat does remove residual acetic acid, at what level of intensity and duration does this effect begin to occur?

Acetic acid evaporates (as does water) well before reaching the boiling point; this is also the reason why you easily smell vinegar when opening the storage bottle at room temperature. At higher temperatures it evaporates faster. As Jean already mentioned, the boiling point of pure acetic acid is approx. 118°C - if you heat a blade to, say, 120°C for more than a few seconds, you can be sure that all acetic acid is gone (if the working space is well ventilated); vinegar is very diluted acetic acid (about 5%) and behaves closer to water. (This explanation is simplified - let me come up with additional data/info tomorrow.)

I'll try to do some better controlled experiments on the amount of corrosion of steel possibly induced by exposure to diluted acetic acid. This will take a bit longer though - please bear with me...

Regards,
Kai

[A. G. Maisey]

Thanks Kai, I look forward to your further information.

However, if acetic acid evaporates and leaves no corrosive residue, is the same true of other acids, for example, say, hydrochloric acid?

Does this evaporate and leave no corrosive residue also?

If acetic acid is permitted to evaporate slowly, at a lower temperature, what is the residue that is left?

[Paul de Souza]

I use lime juice or citric acid as Marco does but it usually leaves a yellow stain on the blade. I don't know how to get rid of it and stays on the blade until it gets the warangan treatment. Any advice?

[Sajen]

Originally Posted by Paul de Souza

I use lime juice or citric acid as Marco does but it usually leaves a yellow stain on the blade. I don't know how to get rid of it and stays on the blade until it gets the warangan treatment. Any advice?

Hello Paul,

like you and Marco I use citric acid for cleaning blades, use hot water and soap to remove the the yellow stain.

Regards,
Detlef