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Vinegar?
Khukuri patina photos
- Thread starter kookery
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Vinegar?
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No, I don't trust lighter acids to work as quickly or evenly as I want them to. I know you can get really even good results out of them as some custom makers use them to creat finished hamon lines, but I don't know how to remove the blotchy uneven patina without also removing the hamon line with it. I use Jasco Metal etch or a generic green Metal preparation etchent. Normally it's contents are phosphoric acid. The key to avoiding the blotchyness is moving the acid around continuously. If you allow it to settle for more then a few seconds it will isolate it's reaction to the area's with the heaviest cover of acid, which will be streaks or pools depending on how much you have sitting on the blade at the time. I tend to rub the blade with an acid soaked rag/towell for about 5-7 minutes and then wipe it completely dry before it gets to the darkness I want it, because it will continue to darken for about a minute after the acid is wiped dry. If you want to be thorough you can wash it off in a baking soda solution to neutralize the acid, then immediately cover it in the oil of your choice to keep rust at bay.
My main purpose in etching isn't to create a permanent patina, it's to see the quality and distribution of the hardening. If the tip isn't hardened at all, I'll tend to be more careful with it since it will deform on impact easier than the sweet spot. If the tip is every bit as bright as the sweet spot I'll be more careful with it since it's as likely to chip as the sweet spot is should it hit a rock near the ground. It's also good to know how high into the blade the hardness goes, if you have a thin ribbon of hardness at the edge thats only 1/8-1/4" tall it's worth being careful when sharpening out nicks and dings as you can easily remove the hardened area with excessive metal removal (mostly in the case of deep chips). If there's a stream of bright hardness that goes from the edge to the spine that can be seen on both sides - you should watch out for any cracks forming at the top or bottom of that line as it is a potential breakage point. This happens when the Kami lets the water run from the edge to the spine accidentally instead of just running straight off of the edge. It can be a lot of water (where you see it on both sides of the blade and it's fairly bright) or a small amount (where it's light and only on one side, just a small increase in surface hardness).
Because I need to be able to see the brightness and the lines of where the water ran to create the hardness I need a clean even patina. Thus the phosphoric acid and the additional techniques for smoothness. What I make isn't as good as custom makers. If you want a long term patina that looks as good as it can it would be worth asking the guys over at the knifemakers forum (or doing a FAQ's and forum search).
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LVC..
So phosphoric acid then? Sounds scary.
I wondered about the line i was seeing on the blade. That is due to a difference in hardness?
I thought it was from the grinder exposing "fresher" metal underneath.
I do like the non-pattern patina you are getting. I might try some vinegar again.... but the time i tried cold vinegar and i got a matt grey finish.
I can see the line now on the Farmcata photo i posted above.. Which is two blotters of mustard. It sort of looks like galvanized steel sheet in person. Thanks for the info on the hamon line, LVC. Now there is even more reason to patina my whole collection.
So phosphoric acid then? Sounds scary.
I wondered about the line i was seeing on the blade. That is due to a difference in hardness?
I thought it was from the grinder exposing "fresher" metal underneath.
I do like the non-pattern patina you are getting. I might try some vinegar again.... but the time i tried cold vinegar and i got a matt grey finish.
I can see the line now on the Farmcata photo i posted above.. Which is two blotters of mustard. It sort of looks like galvanized steel sheet in person. Thanks for the info on the hamon line, LVC. Now there is even more reason to patina my whole collection.
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scratch this post... I need to research what I was going to say more before posting it.
The acid interacts differently with pearlite at the spine and the martensite at the edge, creating a different color.
The acid interacts differently with pearlite at the spine and the martensite at the edge, creating a different color.
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Exactly what I wanted to know. Thanks for sharing this awesome report.
You have obviously done a lot of reading about this topic.
I might stick with the mustard. It works very well as you can see, and i don't have to buy anything extra.
I also don't need a respirator. Yikes! Still sounds scary. I was more worried about pitting the knife, but pitting my lungs sounds even scarier!
And "me too" as far as the mirror polish. I always sand my HI blades down to polish 1500 grit before i try to patina.
The smoother the better for stopping rust. and looks so nice.
You have obviously done a lot of reading about this topic.
I might stick with the mustard. It works very well as you can see, and i don't have to buy anything extra.
I also don't need a respirator. Yikes! Still sounds scary. I was more worried about pitting the knife, but pitting my lungs sounds even scarier!
And "me too" as far as the mirror polish. I always sand my HI blades down to polish 1500 grit before i try to patina.
The smoother the better for stopping rust. and looks so nice.
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Okay, I feel a little better about what I said though I still don't have a concise citeable explanation of it (like out of a chemistry text book).
Phosphoric acid is no worse than hydrochloric acid, both of which are commonly used in chemistry and industry as a reagents. As long as you are wearing nitrile gloves, eye protection and proper ventilation you'll be fine. The hamon line that you see is from the acid interacting differently with the martensitic steel (the hardened edge) and the pearlitic steel (the soft spine).
The acid creates either Fe3O4 (black rust) or in the case of phosphoric acide FePO4. The orange rust you see is Fe2O3. Ferric Oxide (which is always present on iron that contacts air, as Iron is not stable and will immediately interact with oxygen creating FeO (ferric oxide)) can combine to make either Fe2O3 (red rust) or Fe3O4 (black rust, a further oxidization of FeO). This explanation is from: http://www.finishing.com/95/49.shtml
"Hello, perhaps I would be able to answer this question since I majored in Chemistry. First off, as was already explained, rust as you probably are familiar with it is an iron oxide. The red/brown stuff is Fe2O3, or Iron III Oxide with a +3 charge on the iron. However, being a transition metal, iron may also exist with a +2 charge. Oxygen under ordinary conditions only exists with a -2 charge. This means that you can have FeO or Fe2O3. In certain mineral structures you can also have Fe3O4 (This is also an Iron III Oxide.) FeO and Fe3O4 are usually black. Unfortunately, this is not the whole story. Sometimes, molecules of the same chemical can be arranged in different ways or in different structures. Usually one of a few of these forms will predominate, however atoms arranged in different ways will effect light in different ways. For example, you are probably familiar with diamonds and graphite. Technically, they are both made of nothing but carbon atoms. But most people would rather wear a diamond on their finger than a chunk of graphite. Actually, Fe2O3 can exist in a black state, the structure known as Black Alaskan diamond. If I am not mistaken it also plays a role in giving color to other precious gems but since these gem structures involve more than a single type of molecule I will avoid further discussion. If you want to know if you have FeO or Fe3O4, you can try to put a flame to it. FeO should become rust like you know it if it is forced to react with more Oxygen. Fe3O4 on the other hand already has given up all the electrons it can and actually there is something else going on with it that I will not explain. Suffice it to say that 2 of the irons in Fe3O4 are +3 while one is +2, but due to something called resonance the charge is distributed."
It interacts differently with the martensitic steel and the pearlitic steel (I think, further reading necessary to verify as this is just hypothosis with no real citable sources) because the martensite is a much tighter formation that leaves less open iron at the surface. The pearlite is a much looser softer formation that leaves a lot of interstitial spaces on the surface where iron can be taken up by acids and the rust forming process.
One of the problems with patina's is that it creates a rough surface that has a lot more surface space for salts (sweat, blood) and moisture to collect in, which creates a situation that counteracts a lot of the corrosion resistant properties of the stable 'black rust' layer, or patina. That's why I try to keep my khukuri's at a high polish after acid etching them, using the etch as a way to uncover the underlying heat treatment. The polish leaves a very smooth surface with very few pits, scratches, or textured spots for salts and moisture to collect in, reducing the likelyhood of heavy rust from environmental conditions. I know that you can polish a blade and leave the patina as seen on japanese swords, but I've never seen an article or description of how to do so.
Some worthwhile reading:
http://en.wikipedia.org/wiki/Martensite
http://en.wikipedia.org/wiki/Austenite
http://en.wikipedia.org/wiki/Pearlite
http://en.wikipedia.org/wiki/Industrial_etching
http://en.wikipedia.org/wiki/Phosphoric_acid#Rust_removal
http://upload.wikimedia.org/wikiped...Table_of_Elements_showing_Electron_Shells.svg
http://en.wikipedia.org/wiki/Electron_shell
Phosphoric acid is no worse than hydrochloric acid, both of which are commonly used in chemistry and industry as a reagents. As long as you are wearing nitrile gloves, eye protection and proper ventilation you'll be fine. The hamon line that you see is from the acid interacting differently with the martensitic steel (the hardened edge) and the pearlitic steel (the soft spine).
The acid creates either Fe3O4 (black rust) or in the case of phosphoric acide FePO4. The orange rust you see is Fe2O3. Ferric Oxide (which is always present on iron that contacts air, as Iron is not stable and will immediately interact with oxygen creating FeO (ferric oxide)) can combine to make either Fe2O3 (red rust) or Fe3O4 (black rust, a further oxidization of FeO). This explanation is from: http://www.finishing.com/95/49.shtml
"Hello, perhaps I would be able to answer this question since I majored in Chemistry. First off, as was already explained, rust as you probably are familiar with it is an iron oxide. The red/brown stuff is Fe2O3, or Iron III Oxide with a +3 charge on the iron. However, being a transition metal, iron may also exist with a +2 charge. Oxygen under ordinary conditions only exists with a -2 charge. This means that you can have FeO or Fe2O3. In certain mineral structures you can also have Fe3O4 (This is also an Iron III Oxide.) FeO and Fe3O4 are usually black. Unfortunately, this is not the whole story. Sometimes, molecules of the same chemical can be arranged in different ways or in different structures. Usually one of a few of these forms will predominate, however atoms arranged in different ways will effect light in different ways. For example, you are probably familiar with diamonds and graphite. Technically, they are both made of nothing but carbon atoms. But most people would rather wear a diamond on their finger than a chunk of graphite. Actually, Fe2O3 can exist in a black state, the structure known as Black Alaskan diamond. If I am not mistaken it also plays a role in giving color to other precious gems but since these gem structures involve more than a single type of molecule I will avoid further discussion. If you want to know if you have FeO or Fe3O4, you can try to put a flame to it. FeO should become rust like you know it if it is forced to react with more Oxygen. Fe3O4 on the other hand already has given up all the electrons it can and actually there is something else going on with it that I will not explain. Suffice it to say that 2 of the irons in Fe3O4 are +3 while one is +2, but due to something called resonance the charge is distributed."
It interacts differently with the martensitic steel and the pearlitic steel (I think, further reading necessary to verify as this is just hypothosis with no real citable sources) because the martensite is a much tighter formation that leaves less open iron at the surface. The pearlite is a much looser softer formation that leaves a lot of interstitial spaces on the surface where iron can be taken up by acids and the rust forming process.
One of the problems with patina's is that it creates a rough surface that has a lot more surface space for salts (sweat, blood) and moisture to collect in, which creates a situation that counteracts a lot of the corrosion resistant properties of the stable 'black rust' layer, or patina. That's why I try to keep my khukuri's at a high polish after acid etching them, using the etch as a way to uncover the underlying heat treatment. The polish leaves a very smooth surface with very few pits, scratches, or textured spots for salts and moisture to collect in, reducing the likelyhood of heavy rust from environmental conditions. I know that you can polish a blade and leave the patina as seen on japanese swords, but I've never seen an article or description of how to do so.
Some worthwhile reading:
http://en.wikipedia.org/wiki/Martensite
http://en.wikipedia.org/wiki/Austenite
http://en.wikipedia.org/wiki/Pearlite
http://en.wikipedia.org/wiki/Industrial_etching
http://en.wikipedia.org/wiki/Phosphoric_acid#Rust_removal
http://upload.wikimedia.org/wikiped...Table_of_Elements_showing_Electron_Shells.svg
http://en.wikipedia.org/wiki/Electron_shell
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Sorry for the re-write and post. I just hate posting anything that sounds like I'm trying to be 'authoritative' in any discussion or argument if I can't pull up a citation source for it. I am not a chemistry major so I can't verify the information above from previous studies, nor am I an 'authority' on it. The information presented here is all from internet searches.
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The H3PO4 in Coca-Cola is diluted enough that it will not etch or create much of a patina at all. It does remove heavy rust/rust very nicely though.
I used to regularly use it for freeing up bicycle and mini-bike chains years ago.
Very informative. Well done.
Nice job with the paper towel method. Yours came out looking like digital camo, and it's very attractive. I think you must have used nicer paper towels than I did. I wonder if we could get a fabric pattern from nylon or denim? You got the ripple pattern to come through on your paper towels.
Nice. I like the bottom one.
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Those papertowels were cheap walmart brand with just dimple texture. turned out pretty nice.