The Cleaning of Blades

[A. G. Maisey]

Our discussion of blade cleaning that was happening in another thread has now been terminated, due to an infringement of Forum rules, however, I feel that the discussion was progressing in a very valuable direction, and that the cleaning discussion should continue.

The penultimate post, entered by Kai, to that now closed thread I felt was particularly useful for new comers to acid cleaning, accordingly, I have copied Kai's post and I have made it part of this opening post.

Posted by Kai here:-

http://www.vikingsword.com/vb/showthread.php?t=23925

and republished here:-

Hello Alan and Ariel,
Quote:
Any mild acid can be used to get rid of rust, I used pineapple juice for a long time, like about 50 years, but then the stuff I was using became unavailable, the substitute was rubbish, so I went to ordinary household white vinegar, the cheapest I can buy.

Industrially produced concentrated vinegar (glacial acetic acid) is usually cheapest (check both the kitchen as well as the cleaning supply!). It comes in concentrations from 10%-99% - beware, the high concentrations are pretty nasty! Dilute down to 1%-5% to start with (yes, pour the concentrated acid into the water rather than vice versa! ).

Quote:
I use a wall paper trough to soak the blades, inspect daily, rinse daily, scrub with various things depending on what needs to got rid of, pick off the hard encrustations with a sadler's awl, sometimes scrape off big encrustations with a small scraper made from a three corner file.

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).

Quote:
Treatment time can vary from a couple of days to a couple of weeks, I just keep returning the blade to the vinegar until it is clean, sometimes it might be necessary to change the vinegar. I have never known the vinegar to cause any blade damage.

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)!

Quote:
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.

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!)

Regards,

Kai

[A. G. Maisey]

Kai, as I remarked in the opening post to this thread, I consider this post of yours to be quite valuable, however I would like to comment upon it, and I will do that following this post.

Firstly I am going to give a little bit of my own history that relates to keris, and some blade cleaning instructions that I wrote for distribution to people who were on my mailing list. These instructions were written in about 1992 and at that time these instructions were an accurate reflection of the way in which I cleaned blades. Not only keris blades, but all sorts of blades.

In 1992 I had been collecting keris and other edged weapons for about 37 years. I had begun my collecting with the gift of a small collection at age 12, and I had started adding to that collection a couple of years later. By the age of thirty I had something like 3000 keris and other edged weapons in my collection. My objective way back then was to possess every keris ever made. I knew very little in those days, and I understood even less. But I did have a lot of sharp pointy things. Many were incomplete, many were damaged. Most of them required cleaning and restoration, which I did, and which became a permanent hobby.

In my late twenties I began to learn a little bit more about edged weaponry, most especially about keris, and that massive accumulation of junk that I had put together over 15 years or so was gradually fed into auctions and sold by advertisements in the Saturday morning papers. No EBAY in those days.

In the early 1970's I met the man who was later to become Empu Pauzan Pusposukadgo, I also met another Javanese gentleman who was responsible for the maintenance of the edged weapons held by the Yogyakarta Karaton. I knew him as Romo Murdo. From these men I learnt the basics of the way in which Javanese edged weapons were cleaned and stained.


By the age of about 40 my accumulation of edged weapons had been reduced to no more than 40 keris, two very good wakazashis, one extremely good naginata, and an assortment of other odds and ends.

In 1982 at the age of 41 I was accepted by Empu Suparman of the Karaton Surakarta as his pupil. This was when my understanding of keris began, prior to this I had known almost nothing, well, nothing that had much value in any case.

So by a rough reckoning, I have been playing with keris and other edged weapons for at least 65 years. Prior to 1971, when I was 30 years old, I had cleaned a couple of thousand blades, mostly keris. Some of these I had stained, others I had not. In the 47 years since 1971 I think I've probably cleaned at least ten keris blades every year, as well as a few other blades.

Even when I have a blade stained in Solo, I prefer to clean it myself, because most of the people in Solo who stain blades as a job do not clean the blades properly. They do the bare minimum, and often when a newly stained blade is examined under direct sunlight patches of green or yellow will be seen under the black stain. This is the beginning of new rust. If I find this beginning corrosion the blade goes back to the tukang to do again. Usually in a batch of blades that I have not cleaned myself this return rate is around 20% of the first attempt at stain, and 10% of the second attempt, and there will always be a couple of blades after the second attempt that I will need to clean and stain myself.

So these instructions below are a brief and simple explanation of how I clean keris blades. The vinegar that I mention in these instructions, and that I now use instead of pineapple juice is ordinary white cooking vinegar. According to the manufacturer of the brand I usually use, it has an acetic acid concentration of between 4% and 6%, it costs me about $1 for a bottle. I do not use industrial acetic acid, nor do I use imported Italian balsamic vinegar, just ordinary old white cooking vinegar that I can buy in any supermarket.






To clean a rusty old keris blade:-

Actually any mildly acidic agent will do the job. In Jawa the traditional agent is coconut water, but in recent years people have used other acids such as citric, and very dilute sulphuric.

I prefer pineapple juice, which I can buy in 5 litre tins.

Vinegar works well too.

Scrub the blade with detergent and a hard toothbrush under warm running water, to get rid of any surface dirt and oil. Lay the blade in a trough and cover with the cleaning agent.

A plastic wall paper hanging trough is good for this.

Remove the blade each day and scrub it under running water with a hard tooth brush, to remove the rust that the cleaning agent has freed up.

I usually do this twice a day-morning and evening.

After a few days you will find that most of the rust has washed off, but there will probably be still a few small areas that have little bits of hard rust stuck to them. Carefully chip these pieces of rust off with a sharp tool. A small sharp pocket knife blade, or a saddler's needle works well.

Most blades come clean in under a week, but it could take longer.

My experience with pineapple juice is that longer periods in the soak do the blade no harm at all.

Sometimes during hot weather a culture will grow on top of the pineapple juice, and it will start to smell bad. Ignore this, it does no harm---except maybe to your marriage if you have left the trough in the bathroom.

When all the rust is off, wash the blade thoroughly, and if you do not intend to stain it, kill residual acid with bi-carbonate of soda. Paint on a slurry, leave for a few minutes ,thoroughly rinse off. Pat the blade dry, and then leave in hot sunlight, or use a hairdryer to ensure totally dry.

This completes the cleaning process.

[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!

[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?