Forcing a patina on carbon steel?


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burnse
May 16, 2011, 11:40 PM
I gave my Old Hickory kitchen knives and my Opinel 8 a bit of a treatment: I wrapped them in paper towels that were soaked in a 3:2 ratio mix of vinegar and lime juice, and let them sit for about 2.5 hours. I was pretty impressed with the resulting finish and I'm hoping that this will lend some corrosion resistance to my blades.
I honestly wasn't sure what might happen - it just sounded like it was worth a shot, and I figured I'd just do all my carbon knives (if they get ruined, they get ruined together:D). Sorry I have no pics... or camera...

Has anyone else played with something like this on their carbon steel? How did things turn out? Pictures?

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hso
May 16, 2011, 11:44 PM
burnse,

We've had several threads over the years on this. Try sticking it in a jar of French's Mustard on your next effort or a potato or warm Coke.

jahwarrior
May 17, 2011, 12:12 AM
i used a towel soaked in boiled dark vinegar on my Twistmaster, by wrapping it for a few minutes. it came out pretty nicely. i might try a mustard rub next.

mgregg85
May 17, 2011, 12:21 AM
I've heard that you don't want to completely drench the blade, supposedly a light coat works best because you get more air exposure or something. Has anyone else heard this?

burnse
May 17, 2011, 12:39 AM
I actually just looked it up on youtube a short while ago. Some people who stick a blade into something or give a heavy coat of mustard, and leave it for a shorter amount of time, will get a very light patina, or even just an outline of where the acid was.
One video showed a man who completely submerged his blade for a rather long period of time, and he got a very nice, dark coating. Perhaps enough time with a coating makes up for the lack of air available.

Shoot, I need more knives.

kozak6
May 17, 2011, 02:14 AM
I've heard that you don't want to completely drench the blade, supposedly a light coat works best because you get more air exposure or something. Has anyone else heard this?

This is reasonable. The patina is basically iron oxides, and oxygen is necessary to form them.

However, it matters less the more acidic and salty the solution is.

I've used mustard and salt on some kitchen knives. I might take a picture if I remember.

Citrus fruit can potentially make an absolutely gorgeous patina. If you're lucky, you can get the pattern of the "pulp" on the blade and it's can be very impressive.

Wheeler44
May 17, 2011, 09:22 AM
Kiwi fruit will leave a deep purplish blue patina on carbon steel knives.

stan rose
May 17, 2011, 10:02 AM
I have completley cleaned and de-greased carbon steel blades, and then used them to slice fruit, such as apples, and oranges. After slicing I fight the urge to wipe the blades dry for about an hour, then I put protective oil on them. It has worked for me on several knives, gives a nice grey patina, and they don't develop rust freckles as quickly as they used to, proper maintience is still required, especially if you sweat as much as I do.

ArfinGreebly
May 17, 2011, 10:39 AM
A while back I did this process with one of my Case XX large Sod Busters.

This is the "tea & fruit juice blend" method.

And this is the result -- full photo spread here (http://www.noisyroom.net/pix/thr/2008_0401-Knife/Smaller/images.php):

http://www.noisyroom.net/pix/thr/2008_0401-Knife/Smaller/2008_0401-Knife038.jpg

hso
May 17, 2011, 11:14 AM
Metals such as iron are positively charged and slightly reactive; they are less stable than many of their salts, which are a combination of a positive metallic ion and a negative ion such as oxygen or chlorine. So the steel is always seeking a more stable state, i.e. rust.

If you control that oxidation, you can get the iron to combine with a "better" negative ion than oxygen. That can produce an attractive patina. This patina is only a few molecules thick, but it seems to protect the steel a little better from rusting. There is something there in certain fruits and potatoes and acids that provides a reactive environment and just the "right" ions to produce an attractive and protective microlayer. We're all familiar with guns and blueing and browning to control this process further and this is not particularly different.

Sulaco
May 17, 2011, 01:53 PM
I can't remember now which knife it was, but I recently did one in a similar manner. I laid the knife out on a kitchen towel and folded the towel over it so it was covered. I then poured regular old white vinegar all over the towel and let it soak for about 45 minutes. I was happy with the way it turned out. The towel made the finish kind of splotchy so it looked more natural. I think it was a Mora come to think of it. All of my knives get used though, so they develop their own patina over time. This was just to play around.

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