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Thread: Etching with coffee?

  1. #1
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    Etching with coffee?

    On another forum I asked the question how I should etch a laminated carbon blade (plain laminate, no damascus). Apart from the "normal" answer, with ferric chloride, I also got another answer: strong coffee.

    At first I though this was a joke. Then someone provided a pic of a knife etched with coffee. I then thought it was a sediment of the coffee on the knife that darkened the blade. But then more people chimed in, with pictures, and told me the color change was durable.

    Here are some pics from that thread (knives by Toni Oostendorp/Guido van Poppel).

    A knife etched with ferric chloride:



    The same knife, but now etched with coffee (rightmost knife):



    Another blade etched with coffee:




    My question is: what happens here chemically? Is it etching what happens? And how durable is this etching or whatever happens?

  2. #2
    Senior Member EdipisReks's Avatar
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    Coffee is acidic.

  3. #3
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    That is correct. But only barely. Just a little bit more than cow's milk, but less than, e.g., beer. Still we don't etch with beer.


  4. #4
    The most powerful acid in coffee is phosphoric acid which is a commercial etchant. Or perhaps it's creating a very thin phosphate conversion coating?

    Cheers,

    Rick

  5. #5
    Senior Member Benuser's Avatar
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    I use dabbing with hot strong coffee to force a patina on previously degreased carbon blades. Results may vary with the used coffee, though. Remember it will dull the edge as well, so clean the very edge immediately by slicing softly in a piece of cork.

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