Coffee Stains
 

Since I'm notorious for leaving coffee stains everywhere, i felt challenged when i read on a knife-makers forum that coffee gives good contrast on damascus. ;)
So, i selected a Bali tourist/soldier keris, i couldn't successfully stain with FeCl3, and made a lot of coffee....

First i followed the instruction given on the other forum and prepared the coffee with two spoons of instant-coffee per 200mL of hot water. Meanwhile the keris is degreased and etched for 2-5min in citric acid. The keris is then fully submerged in the still hot coffee. The pamor became visible after 2h and reached its maximum contrast after 6h. The result was rather disappointing. After drying the pamor was barely visible.

Next i repeated the procedure with "real" and strong coffee. That lead to the same result after 2-3h.

For the final experiment i added a teaspoon of citric acid to the coffee (about 4L). This gave a remarkably good result after about an hour (see photo). Leaving the keris longer in the coffee proved counterproductive as the contrast began to degrade after the coffee cooled down.

After the promising results i tried to stain the keris from this thread http://www.vikingsword.com/vb/showthread.php?t=13829
with the same mixture. However, this time the result was very poor.

Conclusion: Coffee may for some keris be a viable alternative to FeCl3 but may fail miserably on others.
For good results the coffee has to be hot and slightly acidic.

Best Regards,
Thilo

Since i LOVE coffee i also love this idea. Too bad results aren't consistent (though the results in the photo here look fairly decent) . I guess i'll stick to just drinking mine... ;) :)
BTW, i like your "coffee stirrer"... :)

Hello Thilo,

That's an interesting experiment. I'm not a chemist or a keris professional, but I think what happened is by adding citric acid to coffee (acidic) you are actually increasing the acidity of the solution hence giving you the stain.

Coke are more acidic than coffee, perhaps it (+add some more citric acid) will give a better stain? If not, there's gotta be something in the coffee. :D

Also, perhaps you would like to compare your current staining result with a stain using 4L of hot plain water and 4 tablespoon of citric acid maybe? I used this solution to clean keris and sometimes it also gives a bit of reasonable staining to some keris.

I'm thinking of adding some sulphur (which can also stain) in the solution in the future, but normally to get sulphur easily mixed in the solution we need to add a bit of salt. The salt part is the one that worries me.

Hello Rasdan,

I cleaned this keris with citric acid, so i know what this looks like (a dull grey). Even without citric acid the coffee stained darker. That's the reason it is preferred by knifemakers (who can of course select the steels they are using).
However, I'm not sure what reaction causes the coffee to stain the iron. Main reagent is most likely caffeic acid.
The reaction needs more activation energy than citric acid as it works only when the coffee is hot. The citric acid seems to somehow speed up the reaction. I think when the solution cools down the citric acid becomes the dominant etchant again and slowly degrades the coffee-stain. At least the stain becomes dull grey again after a few hours.

The main reagent of cola is Phosphoric acid. It transforms red iron oxide into black iron phosphate. So it may indeed work. But i am concerned about the sugar. I don't want a sticky keris... ;-)

btw. i'm no chemist either and i guess "keris-professionals" would either use arsenic or have their keris stained professionally ;)

Best Regards,
Thilo

I have not heard of using coffee as a staining agent on mechanical damascus. Interesting.

I've made and stained a lot of mechanical damascus, based on iron or mild steel and 01 steel, sometimes with the addition of nickel. I have usually stained this with ferric chloride, but on occasion I have used other acidic substances such as dilute hydrochloric acid, or ordinary household vinegar.

To test the efficacy of a staining agent it is necessary to begin with new material to be stained, if you do not begin with a new blade, you are not testing the staining agent, you are testing the blade.

With old keris blades, I have had satisfactory results using a variety of staining agents, it seems as if almost any acidic agent will give some sort of result on an old blade, with the result depending more on the blade than on the staining agent. However, the only consistently good results that I have ever achieved have been with arsenic, in one form or another.

Hi Thillo,

Sweet.. So it's something in the coffee :) Higher acidity does not mean better staining obviously.

I always wondered on what exactly happened chemically we when stain a blade and what is the main substance, but I never ventured into finding the answer. :D

G'day Alan,

Do you have any suggestions of other solution that can be used to stain wootz? I have some difficulty in finding FeCL3 here in Malaysia. I am considering of using coffee now. :)

Bill Moran

http://en.wikipedia.org/wiki/William_F._Moran

used hydrochloric acid, as I did myself until I discovered ferric chloride.

In fact, dilute hydrochloric acid , and virtually any other acid, if handled correctly, will give a more realistic and subdued stain than ferric chloride.

If you need a topographic etch before you stain, hydrochloric acid is probably better for this, but in my opinion the nicest finish to damascus is a very light etch that leaves you with a smooth polished surface and a subdued stain, rather than the in-your-face high contrast that most knife show buyers seem to prefer.

Hello Alan,

i was also surprised that coffee is frequently used for that purpose. I guess the reasons are is that it is readily available, requires no safety measures, and can be disposed off in your kitchen sink.
Of course results are more consistent using new blades with well defined steel combinations (e.g. 1.2848 and 75Ni8).
Nevertheless, i thought i would give it a try and share the results :)

@Rasdan
Buying a ton of FeCl3 would probably be no problem anywhere in the world (especially in Malaysia with its electronics manufacturing industry), getting it in small quantities is more difficult.
Here in Germany FeCl3 is available in small quantities at electronics retail stores for PCB etching. But with PCB services becoming less expensive this is a dying hobby. I don't know if there are such store in Malaysia, but i am sure these guys know if there are: http://www.marts.org.my

Best Regards,
Thilo

Thanks Thilo and Alan! :)

Hello Rasdan,

Wootz and pattern welded blades can require pretty different approaches to etching. Granted, also pattern welded pieces can easily damaged by overenthusiastic staining attempts but etching wootz (especially antique pieces) is even more an art. If you really need/want to etch wootz yourself, make sure to search for similar blades (origin and age and wootz type) which are still in stain as a reference. While FeCl3 can be utilized to etch wootz this is by no means the only nor likely to be the single best approach for the majority of antique blades. There's a lot of other etchants which may be suitable or a combination of these may be needed for optimal results (quite a lot of pointers and opinions can be gathered from the net). I'd certainly recommend to try very weak dilutions first even if this needs more patience. If the wootz blade has still a nice original surface which hasn't been polished with power tools, diluted oxalic acid may be worth trying first - just a wild guess though.

Regards,
Kai

Oh yes --- my error.

Rasdan wrote "wootz", I replied for mechanical damascus.

Sorry.

Thanks for the pointers Kai.

I think Alan's explanation would cover wootz as well. :shrug:
I am considering a few options now. Unfortunately I don't have sample blades of same origin. I am thinking of brushing a bit of citric acid on the blade to start with, but I'm not sure. I guess I'll browse and read a bit more on this area on the net. Thanks again :)

Hello Rasdan,

I don't have any wootz blades but i have frequently read that Nital is recommended for etching them. Nital is a mixture of ethanol and nitric acid. You can buy it at chemical suppliers. Don't *ever* try to mix it yoursself, if the concentration of the nitric acid gets to high it tends to explode!

Best Regards,
Thilo

Hi Thilo,

Kaboom!! No, don't want that to happen. Thanks for the advice. It's like you can tell I'm into experimenting things. :) Actually these chemical stuff is pretty hard to get here in Malaysia. There's a nutcase around KL recently goes around splashing people with acid for no reason. He is still at large. So, at the present time, I think if I try to buy any acid without proper papers, I'm certain people would give me a frighten look and dial 911. :D

Rasdan I have had a conversation with a friend who is somewhat of an expert on wootz.

His advice for etching is NOT to touch ferric chloride, he claims that the chloride can damage the steel in the long term --- first time I've heard this, but apparently wootz fanatics believe it to be so.

His recommendation for etching is a 5% nital solution applied with a cotton swab for a brief period of time, starting at 10 seconds and working up.

Rinse off, kill the nital with a slurry of bicarb of soda, rinse, dry, oil.

He did comment that it would be best if the blade could be demounted and immersed fully in the solution, but he recognises that this is not always possible.

Be careful with the cotton swab afterwards.
Cotton and nitric acid is a fun combination :D

I'm no chemist Mr. Wizard, and in this matter I will bow to your superior knowledge if I happen to be incorrect, but my memory of the process for manufacture of gun cotton is that for the combination of cellulose and nitric acid to take place, the nitric acid needs to be free to combine, so it is mixed with sulphuric acid. If the nitric acid is in combination with the ethanol of the nitral, surely it is not free to combine with the cellulose of the cotton?

Is this correct , or am I way off track?

Hello Alan,

You are correct if you want to set up a controlled process to manufacture nitrocellulose (gun cotton) which is relatively stable.
Just combining cotton and nitric acid by itself, may lead to a highy unstable explosive material (xyloïdine).
see page 245 and following in T.L. Davis "The Chemistry of Powder and Explosives" http://www.scribd.com/fullscreen/559...w1m9v49ztfc2bu

If or if not that happens depends on many process parameters (e.g. temperature, concentration, luck). Ditching a cotton rag in nital and then letting it dry is in my opinion like tossing some dice. IMHO the rag should at least be extensively watered before it begins to dry. :)

Nital by itself is a dangerous substance:
http://www.ab.ust.hk/hseo/tips/ls/ls005.htm

Even some on first sight harmless substance like lineseed oil may become dangerous if the safety protocols are not followed: http://www.naturalhandyman.com/iip/i...uscombust.html

Best Regards,
Thilo

Thanks for that Thilo.

I understand where you're coming from.

G'day Alan and Thilo,

Thanks for the advice. I am not actually very keen in using specialised chemical solutions for my blade, for this is the only one I have. But application using cotton swab sounds harmless enough. Anyhow, the blade is still under restoration and wont be ready for staining anywhere soon. I'll check further on the safety part as Thilo mentioned. Again, thanks for the advice.

when I got my first kris I tried the coffee method and results were actually quite good , later on I did have this kris etched with traditional warangan and the results were better but not spectacularly better.

Then I tried the same thing on two KNIL soldiers krises made in Madura , coffee did absolutely NOTHING there just literally a stain which could be washed off with water.

Any pictures?

unfortunately not , I've kept a couple for a while of this experiment on my phone but then I erased them at some point.

I guess that it depens on the metals involved.

Perhaps one of the so many videos on your tube would inspire someone

https://www.youtube.com/watch?v=inGtEynlP0E&t=1215s

It clearly is not one easy thing

Absolutely first class.

Thank you Milandro.

Apparently Instant coffee is more acidic than fresh ground coffee. :shrug:

this is , of course, very difficult to determine.

Apparently Instant coffe and normal coffe MAY have the same acidity

https://theoldcoffeepot.com/is-insta...e-less-acidic/

however there is enormous variation and of course what works under certain conditions may be completely not apt to do the job in another.

I have heard on several videos that people prefer the cheapest possible brand of instant coffe, so the first time I used good instant ( and it worked) while the second time I used Cheap instant ( and it didn’t).

Thanks for that video Milandro! :)

cheers, :)

there are a few more on the subject but none show this method being used on an older kris , all of the videos seem to feature newly forged knives where the damascus pattern is achieved with a known type of steel containing nickel together with steel not containing nickel but I suppose that the composition of traditional metal may have differed considerably from the ones used by modern and mostly western blacksmiths.

this other video seems to use a more scientific approach.
https://www.youtube.com/watch?v=971gfUZLC_0

Cool. Surprising end result! Thanks for that one!

I have been sending some krises to be washed in warangan recently but I had one that I wanted to try to stain with coffee again.

I tried , after bringing the blade to a clean, after putting into coffee for 5 days the blade took a general , slightly, darker appearance with very very very faint staining here and there (although there probably was no “ pamor” to speak of).

Frankly speaking this is definitely my last attempt at staining a kris balde with coffee. It is simply not worth the effort and time.