Help me understand patinas please. CV Case knife on the way

[jon_slider]

Thanks for the clarifications. Yes isopropyl is typically 70% alcohol 30% water, although 99% Isopropyl alcohol is also commonly available.

So far it sounds like red rust requires water, such as high humidity condensation, including that created in a sweaty pocket.

It sounds like drying the blade will prevent rust, especially if it is wiped off on a daily basis, including after washing with soap and water.

It sounds to me like coating the blade with oil will also prevent rust, because the oil prevents humidity from reaching the blade.

Patina is porous and holds oil, so that combination will also prevent water from reaching the blade.

But what about a blade that has patina, for example forced by vinegar, or created by cutting lemons, apples, onions, potatoes, and other foods including steak and foods with tomato like chile relleno or even bbq sauce. Regardless of how the patina got there, patina in itself it does not prevent red rust, unless the patina is oiled.

Imagine a scenario where someone forces a patina with vinegar, then wipes the blade off with 99% Alcohol, and adds no oil to the blade. Then they put the knife in a back pocket and get sweaty due to climate and activity. Now the patina will do little to prevent water condensation from reaching the blade. In fact, since patina is porous, thanks to knarfengs explanation, it could even hold moisture, I think. If the knife gets sweat condensation that is not removed by wiping dry, red rust could result, even with a "protective" patina.

It sounds to me like its not the patina that is doing the protecting. What protects a blade from rust caused by humidity, is an oil film, which Patina is good at holding onto. Or, in the absence of an oil film, the practice of keeping a blade dry, by wiping, or climate, will prevent the moisture from leading to red rust..

It seems wrong science to think a patina is protective against red rust, when in fact it is the act of keeping moisture off the blade by wiping dry, and or oiling, that prevents rust.

and as leghog mentions, bluing will retain oil longer than clean steel, so patina's usefulness is in reducing how often the protective oil layer is applied to a carbon steel blade that does not get wiped dry on a daily basis, due to storage for example, or lack of use.

All Im trying to confirm, is my understanding from my reading of knarfeng's comments, that in itself, patina is not protective, because it is porous and not impermeable to water. That word impermeable, in Spanish, means raincoat. Apparently patina does not act like a raincoat, more like a dry cloth. Dry cloth can get soaked with water, unless it is first soaked in oil.

So Oil is what turns patina into a raincoat , and failure to oil a patina will allow humidity that condenses against a blade, to foster rust. I hope I understood correctly. Thanks for the education.

 

[dma1965]

When I got my knife it looked like this

After some use it ended up looking like this. It was all naturally achieved by cutting fruits and veggies.

I ended up giving it a good cleaning and oiling, using some Flitz and a soft cloth to wipe the blade down. It ended up really shiny, but not as shiny as when it was new. I noticed it has a very pale and thin grey patina now, that acts as a super good protectant.

The point I am getting at is that there seem to be different patinas. One is bold and rough looking, and comes off. It also has an aroma of metal. I call it the young patina. The more aged patina is thinner and does not easily come off, and has no aroma. It becomes a part of the metal, and gets in the pores. Once that happened, it seems that water has little to no effect on the blade. I no longer oil it, and it does not rust.

 

[agile_1]

Thanks for the clarifications. Yes isopropyl is typically 70% alcohol 30% water, although 99% Isopropyl alcohol is also commonly available.

So far it sounds like red rust requires water, such as high humidity condensation, including that created in a sweaty pocket.

It sounds like drying the blade will prevent rust, especially if it is wiped off on a daily basis, including after washing with soap and water.

It sounds to me like coating the blade with oil will also prevent rust, because the oil prevents humidity from reaching the blade.

Patina is porous and holds oil, so that combination will also prevent water from reaching the blade.

But what about a blade that has patina, for example forced by vinegar, or created by cutting lemons, apples, onions, potatoes, and other foods including steak and foods with tomato like chile relleno or even bbq sauce. Regardless of how the patina got there, patina in itself it does not prevent red rust, unless the patina is oiled.

Imagine a scenario where someone forces a patina with vinegar, then wipes the blade off with 99% Alcohol, and adds no oil to the blade. Then they put the knife in a back pocket and get sweaty due to climate and activity. Now the patina will do little to prevent water condensation from reaching the blade. In fact, since patina is porous, thanks to knarfengs explanation, it could even hold moisture, I think. If the knife gets sweat condensation that is not removed by wiping dry, red rust could result, even with a "protective" patina.

It sounds to me like its not the patina that is doing the protecting. What protects a blade from rust caused by humidity, is an oil film, which Patina is good at holding onto. Or, in the absence of an oil film, the practice of keeping a blade dry, by wiping, or climate, will prevent the moisture from leading to red rust..

It seems wrong science to think a patina is protective against red rust, when in fact it is the act of keeping moisture off the blade by wiping dry, and or oiling, that prevents rust.

and as leghog mentions, bluing will retain oil longer than clean steel, so patina's usefulness is in reducing how often the protective oil layer is applied to a carbon steel blade that does not get wiped dry on a daily basis, due to storage for example, or lack of use.

All Im trying to confirm, is my understanding from my reading of knarfeng's comments, that in itself, patina is not protective, because it is porous and not impermeable to water. That word impermeable, in Spanish, means raincoat. Apparently patina does not act like a raincoat, more like a dry cloth. Dry cloth can get soaked with water, unless it is first soaked in oil.

So Oil is what turns patina into a raincoat , and failure to oil a patina will allow humidity that condenses against a blade, to foster rust. I hope I understood correctly. Thanks for the education.

An added complexity is that the conditions under which black oxide forms are not conducive to the formation of red oxide. So if you keep your blade dry, it may not form red rust, even if you don't oil it.

I think your analysis is correct as far as it goes. And knarfengs thoughts on oil filling in the pores of a patina to prevent water from entering is a key point. Something has to keep water away from the blade surface - and I think that ends up being oil whether the blade is patinated or not.

If I think about a patina at the microscopic level, I imagine something like a sponge or a casting created with the lost wax process. Hundreds of thousands of thin walled tunnel like structures. Once something (water or oil) gets in there it is hard to get out. Oil, being less reactive than water probably just kind of sits there and plugs things up. I would expect water to be much more reactive and that the O would bond to something along/in the tunnels. It is likely a few water molecules left from washing would never even reach the surface of a well patinated blade. Immersing the blade in water or sweat for extended periods is a different story.

But I am just postulating (wild imaginings) here. The mechanisms for patina and red rust formation are probably quite complicated and varied on the microscopic level. Thinking about what happens on the atomic level makes my head hurt .

That is a beauty dma1965. Love the scales and the patina is nice and even looking. Interesting technique for forming a nice uniform patina. Does it require periodic treatments to maintain the uniform gray patina?

 

[jc57]

Here's how I treat my CV steel blades. I use them for whatever I use a knife for. if that involves cutting fruit, a patina tends to develop. After food prep type things, if possible I will rinse off with water and then wipe dry. If not, I'll just wipe it off.

Occasionally I'll add a little lubricant or protectant of some kind to the knife, wiping off any excess. About once a week or so I'll polish the blades with some Simichrome polish and a soft paper towel. This removes some but not all of the patina, leaving a shiny blade surface with some metal discoloration. Then oil again. Since I tend to rotate to a different knife about once a week, the shine and oil usually occurs at the end of the week, maybe in conjunction with sharpening.

I still get a patina, but it's a more subtle thing.

 

[agile_1]

Here's how I treat my CV steel blades. I use them for whatever I use a knife for. if that involves cutting fruit, a patina tends to develop. After food prep type things, if possible I will rinse off with water and then wipe dry. If not, I'll just wipe it off.

Occasionally I'll add a little lubricant or protectant of some kind to the knife, wiping off any excess. About once a week or so I'll polish the blades with some Simichrome polish and a soft paper towel. This removes some but not all of the patina, leaving a shiny blade surface with some metal discoloration. Then oil again. Since I tend to rotate to a different knife about once a week, the shine and oil usually occurs at the end of the week, maybe in conjunction with sharpening.

I still get a patina, but it's a more subtle thing.

Another interesting technique. This is great info folks. Thanks for sharing. :thumbup:

 

[jc57]

Another interesting technique. This is great info folks. Thanks for sharing. :thumbup:

I kind of think of it as "resisted but inevitable patina". I don't go nuts with a buffer and compound to get it back to the original mirror finish. I can do that if I want to, but I prefer to stick with what I can achieve with elbow grease.

 

[dma1965]

I think your analysis is correct as far as it goes. And knarfengs thoughts on oil filling in the pores of a patina to prevent water from entering is a key point. Something has to keep water away from the blade surface - and I think that ends up being oil whether the blade is patinated or not.

If I think about a patina at the microscopic level, I imagine something like a sponge or a casting created with the lost wax process. Hundreds of thousands of thin walled tunnel like structures. Once something (water or oil) gets in there it is hard to get out. Oil, being less reactive than water probably just kind of sits there and plugs things up. I would expect water to be much more reactive and that the O would bond to something along/in the tunnels. It is likely a few water molecules left from washing would never even reach the surface of a well patinated blade. Immersing the blade in water or sweat for extended periods is a different story.

But I am just postulating (wild imaginings) here. The mechanisms for patina and red rust formation are probably quite complicated and varied on the microscopic level. Thinking about what happens on the atomic level makes my head hurt .



That is a beauty dma1965. Love the scales and the patina is nice and even looking. Interesting technique for forming a nice uniform patina. Does it require periodic treatments to maintain the uniform gray patina?

No, I really don't do anything special. I use it and when it gets a little dull I strop it and it gets shiny, with a pale grey tone to it. To me the whole purpose of patina is so I can forget about worrying about it.

 

[jon_slider]

After some use it ended up looking like this.

… it has a very pale and thin grey patina now, that acts as a super good protectant.

… there seem to be different patinas. One is bold and rough looking, and comes off. It also has an aroma of metal. I call it the young patina. The more aged patina is thinner and does not easily come off, and has no aroma.

… it seems that water has little to no effect on the blade. I no longer oil it, and it does not rust.

Beautiful knife!
good looking patina
and excellent observations about the smell, taste, and staining of food caused by young patina

> acts as a super good protectant
> water has little to no effect on the blade. I no longer oil it, and it does not rust

those two statements are not scientific, they are not supported by any facts. Not trying to argue, but based on knarfengs comments, blades that stay dry don't rust, even if they have no patina.

So a blade with patina, that is not oiled but stays dry and does not rust, cannot be said to be because of the patina. It could be because the blade stays dry. Also stropping will remove anything on the surface, including water condensation.

So I would say the reason your knife does not rust, is not necessarily because it has a nicely seasoned patina. It could just be that your blade does not stay wet, or does not get wet in the first place.

Your stag knife collection is stunning! Thanks for the pics. Thanks to you, Ive been sniffing my patina. And like you, I also strop my blade back to shiny from time to time.

here it is after stropping clean

and then repatinaed by food.

stopped clean again

repatinaed again

and more

as you can see, the blade does not rust, even when the patina is removed or replaced repeatedly. I would say the reason it does not rust, is that it is never left wet. I wipe it off after using it, and it gets used daily, so its constantly getting wiped dry.

I could say the reason it does not rust is because the patina protects it, but I have no evidence of that.

 

[dma1965]

Beautiful knife!
good looking patina
and excellent observations about the smell, taste, and staining of food caused by young patina

> acts as a super good protectant
> water has little to no effect on the blade. I no longer oil it, and it does not rust

those two statements are not scientific, they are not supported by any facts. Not trying to argue, but based on knarfengs comments, blades that stay dry don't rust, even if they have no patina.

So a blade with patina, that is not oiled but stays dry and does not rust, cannot be said to be because of the patina. It could be because the blade stays dry. Also stropping will remove anything on the surface, including water condensation.

So I would say the reason your knife does not rust, is not necessarily because it has a nicely seasoned patina. It could just be that your blade does not stay wet, or does not get wet in the first place.

Your stag knife collection is stunning! Thanks for the pics. Thanks to you, Ive been sniffing my patina. And like you, I also strop my blade back to shiny from time to time.

here it is after stropping clean

and then repatinaed by food.

stopped clean again

repatinaed again

and more

as you can see, the blade does not rust, even when the patina is removed or replaced repeatedly. I would say the reason it does not rust, is that it is never left wet. I wipe it off after using it, and it gets used daily, so its constantly getting wiped dry.

I could say the reason it does not rust is because the patina protects it, but I have no evidence of that.

I have to agree with about 90% of what you say. I have a lot of brand new (as in never carried or used) USA made Winchester knives (the ones made by Queen), which are reputedly 1095 high carbon steel. I learned (the hard way) that the shiny knives with no patina will rust if they get a fingerprint on them. The ones that I put a patina on with food and strop shiny again handle fingerprints with no problem. I had one I put away after shining up, and did not use it for months, and when I took it out I noticed the big fingerprint, and cringed at fist, but then I just wiped it off and there was no trace of it left, and no rust.

Regarding not worrying about my blade rusting, I also noticed that a non-patina blade (e.g. a brand new knife I carried) and got wet, it would rust. It would also rust from pocket sweat. Once I got the patina on the knife, even if it is stropped shiny, it would not rust. Sometimes it would get darker at that spot (which is black rust...or patina), but not red rust or any pitting.

 

[jon_slider]

I learned (the hard way) that the shiny knives with no patina will rust if they get a fingerprint on them. The ones that I put a patina on with food and strop shiny again handle fingerprints with no problem. I had one I put away after shining up, and did not use it for months, and when I took it out I noticed the big fingerprint, and cringed at fist, but then I just wiped it off and there was no trace of it left, and no rust.

Regarding not worrying about my blade rusting, I also noticed that a non-patina blade (e.g. a brand new knife I carried) and got wet, it would rust. It would also rust from pocket sweat. Once I got the patina on the knife, even if it is stropped shiny, it would not rust. Sometimes it would get darker at that spot (which is black rust...or patina), but not red rust or any pitting.

Good info! Sounds like you do indeed have evidence that stropping prevents rust. I have heard that before.
And thanks for your testimonial that your blades are exposed to sweat, and they rust when new, but not after stropping.

As you can see, Im still skeptical about unoiled patina being the source of rust prevention, as that would contradict knarfengs science based comment that patina is porous and only protects if oiled.

I guess we need a new test. Get a new blade, sweat on it to prove it will rust, then strop it, but dont patina it, and see if it prevents rust in the same sweating scenario.

In any case, I like your strategy of stropping down young patina, and Im glad you have found a way to prevent rust. Jury is still out whether the protection comes from the dry patina, or from the smoothing effects of the stropping compound. A case could be made that smooth blades rust less, but I have not done a test, just a guess.

Thanks for the exploration. Like you, I will continue to strop and polish my blade patina from time to time. I like your comments about young patina, and I agree that a stropped blade does not smell nor stain like young patina. Im getting hungry, time to go work on my patina building

 

[mnblade]

Interesting points, all. It might be a good time, however, to sort of remember that rust ain't cancer. Knives get some rust on 'em. You knock it off and move on with your life. Spots and light surface-rust (in other words MOST of the rust you'll get on your knife) can be nuked with a little spit and vigorous rubbing from a t-shirt or handkerchief or napkin or what have you. More serious rust might call for a little steel wool, or Flitz, or fine-grained sand paper. Easy to fix. If you're not up to this level of maintenance, there's no shame in going stainless.

-- Mark

 

[Obsessed with Edges]

Good info! Sounds like you do indeed have evidence that stropping prevents rust. I have heard that before.
And thanks for your testimonial that your blades are exposed to sweat, and they rust when new, but not after stropping.

As you can see, Im still skeptical about unoiled patina being the source of rust prevention, as that would contradict knarfengs science based comment that patina is porous and only protects if oiled.

I guess we need a new test. Get a new blade, sweat on it to prove it will rust, then strop it, but dont patina it, and see if it prevents rust in the same sweating scenario.

In any case, I like your strategy of stropping down young patina, and Im glad you have found a way to prevent rust. Jury is still out whether the protection comes from the dry patina, or from the smoothing effects of the stropping compound. A case could be made that smooth blades rust less, but I have not done a test, just a guess.

Thanks for the exploration. Like you, I will continue to strop and polish my blade patina from time to time. I like your comments about young patina, and I agree that a stropped blade does not smell nor stain like young patina. Im getting hungry, time to go work on my patina building

There's no hard & absolute answer. I too have noticed that a patina can definitely slow down the onset of other corrosion. What Frank (knarfeng) said is right, it's not a guarantee or a permanent fix. But it can make a difference, sometimes a significant one. I've mentioned it before, but I've seen the difference in forcing a patina on the clip blade of my Schrade 8OT stockman (1095 steel), while leaving the spey and sheepsfoot blades alone. The un-patinated blades have accumulated some spots with some 'red' in them, while the patinated clip blade looks as fine as ever, without the spots. I used a mix of vinegar & hot water to do mine, and this was some months after I'd initially experimented with some pickle juice (contains vinegar) to do the same thing on the same blade. On areas that previously had patina from the pickle juice, the 2nd process with the vinegar/hot water just made the existing patina darker and more even. The areas near/on the tang of the blade that previously had no patina showed a little red rust, which ended abruptly at the line between the un-patinated steel and the patinated steel. That was an eye-opener.

Regarding stropping, it'll both scrub off existing oxidation (either black or red), and the polishing of the steel will help reduce the size of the pores and other irregularities in the finish that tend to accumulate and hold moisture and other rust-making stuff. It's known that a higher polish on steel is one way to reduce it's susceptibility to corrosion/oxidation. This is also why a polished blade will patinate more slowly than one with a rougher or un-polished finish (like satin, for example).


David

 

[digital9ja]

When I got my knife it looked like this

After some use it ended up looking like this. It was all naturally achieved by cutting fruits and veggies.

I ended up giving it a good cleaning and oiling, using some Flitz and a soft cloth to wipe the blade down. It ended up really shiny, but not as shiny as when it was new. I noticed it has a very pale and thin grey patina now, that acts as a super good protectant.

The point I am getting at is that there seem to be different patinas. One is bold and rough looking, and comes off. It also has an aroma of metal. I call it the young patina. The more aged patina is thinner and does not easily come off, and has no aroma. It becomes a part of the metal, and gets in the pores. Once that happened, it seems that water has little to no effect on the blade. I no longer oil it, and it does not rust.

Man, I love that look. Makes me think of burnt french toast. One morning I was elk hunting up on the Mogollon Rim and came across a big dead tree that had been struck by lightning. It had that same burnt french toast look. Made me so hungry I had to take a picture of it! You better watch out or I'm gonna pour some fresh Michigan Maple syrup on those scales! I'd like to know the details of that knife if you care to share!