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Patina... really?

Discussion in 'Maintenance, Tinkering & Embellishment' started by mantzao, May 14, 2012.

  1. mantzao

    mantzao

    Jun 16, 2011
    Hello guys:)

    I don't get why somes folks like patina on their blades:confused:
    I don't know much about it but isn't that some form of rust?
    Is it it safe for you health to prep food with a patina blade?
    Really, i'm not trying to be stupid or anything but what's the appeal of it to you?

    thanks in advance
     
  2. stabman

    stabman Gold Member Gold Member

    Sep 17, 2007
    It's a form of oxidation, but not the ugly red rust type.
    It helps against forming that ugly red rust...at least a bit.
    It makes it look more used, and if you actually use your carbon steel knives, a patina will develop in almost all cases. Some people like the "actually used" look.
    It's as safe to use on food as it was without a patina. For carbon steel kitchen knives, the patina forms from cutting food.
    Stainless or glass knives are better for fruit if you don't like the taste which a carbon steel blade can impart to those citrus laden foods.
     
  3. SPNKr

    SPNKr

    139
    Jun 11, 2011
    To prevent rust. Patinas (FeO) don't flake off or spread like red rust (Fe2O3) does. I live in the tropics, so it is important.

    I'm not sure how it affects food prep, besides the taste. I'm interested in it too.
     
  4. knarfeng

    knarfeng senex morosus moderator Staff Member Super Mod Moderator

    Jul 30, 2006
    If patina really protected steel, it would be a required finish on commercial steel. It isn't.

    Patina is rust. It just isn't red rust.
     
  5. w.t. anderson

    w.t. anderson Gold Member Gold Member

    Aug 2, 2007
    But isn't it a CONTROLLED rust, like the old process of browning firearms, that protects the surface of the metal?
     
  6. DrPenguin

    DrPenguin

    463
    Mar 2, 2005
    I sometimes forget that there are so many folks who really didn't grow up where carbon steel was the overwhelming favorite when it came to knives. Mine is probably the last generation for which that was true... middle age will soon sneak up on me damnit! :p

    In answer to your questions it is a form of rust but a slightly different chemical composition. The patina molecule is stable and does not expand the surface of steel like regular rust... so you don't get the ongoing pits forming under it. It won't eat into a metal and keep going.

    Is it safe? Oh yeah. no health problems but is ~can~ impart flavor to food. In my experience some carbon steels do this much more than others. I've found patinas do almost eliminate it. But I cannot tell you if that is true for all carbon steel knives or just the ones I own.

    Does it protect steel.... uh maybe, lol. I think it does but I've only seen it when the patina is deep. IOW just slicing up a tomato or two ain't gonna help you. I believe a real patina takes a long time or a lot of use to form. A decent stain can be made pretty quickly OTOH. When my old EDC was new it got taken out on a sweaty hike in 90+ temps and had a pit on it when I got around to cleaning it that evening. But years later when it had that light grey deep patina that you turn into the light and it doesn't change color? No worries. Carried it lots in the same conditions and it never happened. Am I sure that was the cause? No, but I think it helped. You ask a lot of knowledgable guys and you'll get lots of different opinions.... I am not sure enough to contradict them just reporting what I've seen.

    Will
     
  7. The Government

    The Government

    Aug 21, 2009
    I react the same way to carbon steel knives without patinas. "No patina, Really?":D

    There is nothing wrong with trying to keep your blade oxidation free -but for some (myself included) it is an exercise in futility. Especially if you consider your knife a user.

    Imagine if in the Die Hard movies John McClane's shirt never got torn up and covered in dirt and blood. What if he just stayed clean and sterile throughout the entire movie? :D
     
  8. patina = chemically 'Fe[SUB]3[/SUB]O[SUB]4[/SUB]' = 'black' oxide formed by reaction of iron + oxygen (non-destructive; thin oxide surface layer slows reaction of the iron to oxygen & moisture, which helps protect the steel somewhat)

    rust (the 'red' kind) = chemically 'Fe[SUB]2[/SUB]O[SUB]3[/SUB]' = red oxide formed by iron + oxygen in the presence of water (destructive, penetrates deep into the steel; molecules of rust occupy greater volume than original molecules of steel, then disintegrates --> pitting)

    To highlight the difference, the 'black' iron oxide (patina) is completely non-destructive. The oxide layer forms at the surface, and the reaction stops. The 'red' iron oxide (rust) is completely destructive, given enough time. The reaction doesn't stop until all the iron has been consumed. A 'forced patina' is potentially a dangerous thing, because of the acids used to do it (which also pit the steel). If not properly controlled, cleaned & neutralized, the acids can do the same damage as rusting. A 'natural' patina formed by exposure of the steel to the air (oxygen), would be the least damaging. It just takes more time. :)
     
    Last edited: Jun 10, 2012
  9. Ken44

    Ken44 Gold Member Gold Member

    Jun 29, 2005
    To protect my carbon steel knives. Not for looks. I live in the humid south, and me touching the blades just a few times will often leave me with some pitting, or very small rust(bad type) specs.
    I can put a patina on one and touch/use the blade for close to a year without having to worry one bit about the steel.

    I guess I could apply oil to the blade very often, but I don't really like having to worry about that, and with a good patina I don't.
     
  10. Shotgun

    Shotgun

    Feb 3, 2006
    I don't know if it's age necessarily. I showed an old timer what knife I was getting and when I told him it was NOT stainless steel he said something like: "Oh, so it doesn't hold an edge very long.":rolleyes: I'm less then half his age and love carbon steel. I don't use stainless, even in the kitchen.

    As to the OP: I dunno. My parents have had this carbon steel knife in there kitchen drawer longer then I've been alive and has been through several dishwashing cycles and has generally been totally neglected. It has a nice dark grey patina and no rust. Pick up one of the stainless knives under it and your more likely to see rust on it. Same care to both and not a drop of oil has touched them in 35+ years. Does it protect knives? I can't give you a definite, scientifically accurate answer. I can say that through my informal observation with that knife and the carbon steel I currently own, that it does in fact protect it from going orange. However just like stainless knives it's not impervious to it either.
     
  11. flatblackcapo

    flatblackcapo Gold Member Gold Member

    Mar 25, 2012
    for me it was a easy/cheep way of making my knife non reflective.
     
  12. clockman

    clockman Gold Member Gold Member

    Jan 14, 2009
    I have Gayle Bradley with a forced patina.

    I like it Much better with a patina than without.
     

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