[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?