Particularly Puzzling Patina Phenomenon

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Jan 7, 2009
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I hope somebody can explain what is going on to me!

Here is a summary of the events of the last few days, to the best of my recollection...

Last week I got my Spyderco Gayle Bradley in the mail, I had been eagerly awaiting it and was not let down. It was smooth and well constructed like all Spyderco's I've owned but it just felt so... solid. I decided it was going into my rotation immediately and put it right into my pocket. :D

After seeing photos of other people's Gayle Bradleys with dark looking forced patinas I decided to give it a shot, I picked up a bottle of apple cider vinegar and submerged the blade in it overnight.

The next morning I jumped out of bed and ran downstairs to check on my new patina. When I pulled it out of the vinegar I wasn't sure it looked any darker at all, maybe enough time hadn't passed yet?

After about two more days the blade was a little grey but still wasn't dark like I'd seen in pictures online, other people had achieved a completely black blade, which is what I was shooting for.

At this point in time I took a quick picture on my cell phone for color reference, here it is next to a regular blade, they looked the same before the GB's vinegar bath.

IMG-20120707-00145.jpg


Frustrated, I looked online and found someone suggesting cola instead of vinegar, and I rinsed the blade off with water and threw it into a glass of flat Pepsi.

The next morning is when something puzzling occurred, I removed the blade from the Pepsi and it looked slightly darker, but when handling it my fingernail 'scratched' the blade and left a black mark. It was like I was scratching silver paint off an underlying black surface. I scratched my fingernail vigorously across the entire blade to see what would come off, and the result can be seen here (with another blade for comparison):

IMG-20120711-00152.jpg


I couldn't get any more of the 'silver' to come off so I put in back in the Pepsi bath. This morning was about 48 hours later and the blade looks the same:

IMG-20120711-00153.jpg


Can anyone explain to me what's going on? Maybe this is a normal or uncommon but well known result? I have no experience with non-stainless blades and patina outside of seeing pictures online and the events above.

Note: when submerging the blade in vinegar the first time I applied lip balm to the pivot and edge to try and prevent patina from forming there. (Didn't seem to work so I wiped it off)

If this in unusual can someone hypothesize what happened? And propose a solution or a course of action that would yield an improvement or at least more information?

Should I use acid (FeCl or whatever?) to etch the blade? Should I try to polish it? I'm at a loss at this point...

Thanks for reading, I know it was long, but I hope it was also interesting and puzzling to someone other than me.
Sorry for the cellphone pictures, I'll get a better picture of the current condition of the blade tonight after work (I put it back in the Pepsi for now).
 
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Well it's uglier than homemade soap but likely no worse for the wear. Looks like the blade blackened like crazy with a top layer of oxidation that can be scraped, rubbed off. You'll get a seasoned patina pro that can give more advise I'm sure.
 
Any chance the GB had some sort of oil, lacquer, wax, or other light ant-corrosion coating? That would explain why the part you scratched got darker afterwards.
 
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Any chance the GB had some sort of oil, lacquer, wax, or other light ant-corrosion coating? That would explain why the part you scratched got darker afterwards?

That's something that crossed my mind. The previous owner won't answer my emails so I can't say for sure.

I've tried to scratch the rest of the blade (several times) to no avail.

The coating I scratched looked the same as the rest of the blade does now, you could still see the brushed finish but it was slightly darker than factory.

One other thing, the blade smells bad now. Like vomit and pennies :confused:
 
Ok, so the blade is cpm-m4? The blade most likely had a layer of oil because since its not a SS blade and its a carbon steel. The oil might have come off and like RetiredGuns said created an oxidation by seeping under the coating and creating that so the coating was "floating" on the oxidation. the reason it smells like "pennies" is because the patina is a fancy word for rust. I dont know why it smells like vomit though.
This is just my guess on what happend.
 
I'd get some mothers wheel polish or flitz and polish the hell out of it until it has a uniform appearance, then use some hot water and soap to remove any polish and oils...then you'll be free to try the patina again with a prepped surface if you want.
 
It's very important to thoroughly clean the blade before forcing any type of patina. Use something like acetone to remove any surface contaminants to ensure that the etching solution does its job. As someone above said, you can scrub the blade with some 000 steel wool to remove your previous efforts, then really clean the blade. Here's my CPM-M4 blade with a forced patina, done by SoLo:

2011-11-23_10-34-56_959.jpg
 
A patina is a layer of rust.

Some rusts, like the red stuff you see on old iron antiques, can flake off. This does not "damage" the blade in a true sense, but you're losing material when this happens, since iron has at that point formed iron oxide with water and oxygen in the air. Some don't flake off at all. The patinas that adhere to a blade are the ones that are useful, because they block the rest of the steel from further reactions.

Research the steel that was used in your knife. Some steel form patinas more slowly than others. Carbon steels typically form them faster than stainlesses.
 
Exact same thing happened to my M4 Military, vinegar only. All of my silver top layer scraped off, fairly even black underneath
 
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