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Thread: Should I force a patina on new knife?

  1. #1
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    Should I force a patina on new knife?

    I have two new Konosuke White #2 knives.
    I read the patina they eventually develop provides a small amount of rust protection. (Is this a myth?)
    I've also seen videos where people use mustard (or vinegar) and water to intentionally speed up a patina.

    Is there any advantage to just letting the patina develop naturally and slowly over time?

    My cast iron pans have a wonderful durable non-stick finish after years of oiling/seasoning after every use.
    I believe this old patina cannot be accelerated; you must be patient.
    I'm wondering if people do the mustard/vinegar thing purely for cosmetic reasons - or for the health of the knife.

  2. #2
    Senior Member mpukas's Avatar
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    Patina on a knife is completely different to the seasoning on an old cast iron pan - that comes from long term us of cooking oil being "absorbed"a nd burned onto the surface of the iron, and not being completely washed off. Patina is a reaction from steel to acid elements in different foods. There is no build-up of a surface film.

    Forcing a patina is up to you - you can do it for aesthetic reasons, to get a certain look. Or you can do it if you find the steel is reacting to foods prior to developing a patina on it's own. However your patina comes around, it will help protect the steel from rust (somewhat but not totally) and further reacting to foods.

    I've also heard that forcing a patina w/ very acid products can actually dull a very fine edge. The acid basically eats away the fine metal. Not sure if this is really true - or even much of a concern - but makes some sense to me.

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    Quote Originally Posted by mpukas View Post
    Patina on a knife is completely different to the seasoning on an old cast iron pan - that comes from long term us of cooking oil being "absorbed"a nd burned onto the surface of the iron, and not being completely washed off. Patina is a reaction from steel to acid elements in different foods. There is no build-up of a surface film.

    Forcing a patina is up to you - you can do it for aesthetic reasons, to get a certain look. Or you can do it if you find the steel is reacting to foods prior to developing a patina on it's own. However your patina comes around, it will help protect the steel from rust (somewhat but not totally) and further reacting to foods.

    I've also heard that forcing a patina w/ very acid products can actually dull a very fine edge. The acid basically eats away the fine metal. Not sure if this is really true - or even much of a concern - but makes some sense to me.
    When you wrote, "if you find the steel is reacting to foods prior to developing a patina on it's own", what is this reacting you speak of?
    Isn't this reacting just the patina-forming process?
    Or are you talking about a huge reaction, like rust?

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    I would let the patina set naturally, unless you're having rust problems. A natural patina is a beautiful thing. If a patina must be forced, I prefer phosphoric acid. Phosphoric acid reacts to iron and forms a very rust resistant oxide. The only negative with phosphoric acid, is it leaves a dull grey finish.

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    I believe he speaks of food discoloration due to reactions with the steel i.e. brown onions, sulfur like aromas.

  6. #6
    Senior Member stevenStefano's Avatar
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    Depends what you're cutting. If you cut a lot of onions and that, forcing a patina is a necessity unless you like red onions turning into black onions. If it's just meat and that sort of thing though I'd just let it develop naturally

  7. #7
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    The knives will be used for everything in a home kitchen.
    Are such onions, turned black, in any way unsafe to eat or just a temporary aesthetic annoyance.
    This ain't no restaurant and if the family won't eat what I cook I just beat them more.

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    Quote Originally Posted by mpukas View Post

    I've also heard that forcing a patina w/ very acid products can actually dull a very fine edge. The acid basically eats away the fine metal. Not sure if this is really true - or even much of a concern - but makes some sense to me.
    That can happen. The funny thing is that the diluted ferric chloride that most of us knifemakers use to etch damascus or highlight a hamon actually seems to etch fully hardened martensitic steel more aggressively than steel in its "softer" states. The net effect of the patina is that you either turn the "bad" orange oxides (aka rust) into the "good" black oxides as in the case of old fashioned rust blueing or you just go straight to the good ones, hopefully bypassing the orange rusting stage like you would with a modern hot or cold blueing method. Some guys alternate blobs of mustard and selenium based cold blueing paste to get an interesting effect on field knives, but I don't know that I would want to use the cold blue stuff on a kitchen knife.

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    I vote go natural and don't worry about it. Just cut your onions quickly and wipe you knife if you start with your knives fresh outta the box.

    -AJ

  10. #10
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    In my experience the Konosuke white #2 steel isn't as reactive as the SK-4 in a Fujiwara, for example. You shouldn't have any problems with food discoloration.

    I used mustard on a fingertip to force a patina on it for appearance.

    “I hear and I forget. I see and I remember. I do and I understand.”

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