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Thread: Ever seen green in walnut?

  1. #1
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    Ever seen green in walnut?

    I was milling some black walnut yesterday and we saw these green streaks in the sapwood adjacent to the heartwood as the slabs came off the mill. They disappear over time. Anyone know what causes it?

    John

  2. #2
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    Certainly seen it, purple too, even more often. I don't know the mechanism but I strongly suspect redox chemistry, perhaps involving copper salts given how quickly it disappears with exposure to oxygen. Actually, thinking a bit, 2+ iron (ferrous) might be a better guess--ferrous chloride, for example is a brilliant green. Much more common, it should quickly go to 3+, ferric oxide aka rust, which is red when exposed to oxygen. Chromium will also give a nice green, but that seems less likely to be in wood.
    Last edited by roger wiegand; 04-14-2021 at 3:40 PM.

  3. #3
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    just a guess here, maybe someone once nailed copper nails into the tree trying to kill it

  4. #4
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    I have seen the green on several logs from multiple trees on this job and have not hit metal of any kind.

  5. #5
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    Iron would just be from ions in the water in the soil, not present as solid metal. I don't know what the source of reducing equivalents to get it from iron (III) to iron (II) might be. Perhaps anaerobic bacteria doing some sulfur chemistry. I'm guessing the inside of a tree trunk might be pretty oxygen-free. Interesting question, google has so far not shed any light on the answers.

  6. #6
    When the boards are milled there are bacteria in the wood that are exposed to the air for the first time. They overdose on oxygen and bloom, hence the green color, but soon die off and those areas turn brownish again.

  7. #7
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    My father cut hundreds of walnut trees.... iron nails, etc always had black streaks, not green...
    Have cut up a lot of walnut on my mill... same thing, if I saw a black streak then I knew a nail or
    something iron was in tree.... (had blades to show it sadly)...

    Have seen many colors in walnut but never green...
    Let us know if it turns to a different color now that it is exposed to air and light... very curious...

  8. #8
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    Quote Originally Posted by Tom Hogard View Post
    When the boards are milled there are bacteria in the wood that are exposed to the air for the first time. They overdose on oxygen and bloom, hence the green color, but soon die off and those areas turn brownish again.
    Awesome tidbit of information.

    I love this stuff.

  9. #9
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    Quote Originally Posted by Tom Hogard View Post
    When the boards are milled there are bacteria in the wood that are exposed to the air for the first time. They overdose on oxygen and bloom, hence the green color, but soon die off and those areas turn brownish again.
    Hi Tom. That's really interesting. Where did you learn that?

    John

  10. #10
    A similar question came up on another forum many years ago. More than 50% of the logs I saw are walnut and it was something I see frequently so, when an expert (I'm not sure I remember which one), provided that explanation. It is not seen in every log, it probably would be seen throughout the boards but it is easier to see on the lighter sapwood.

  11. Fur sure

    But I would say the proper term for it is turquoised walnut. Very ephemeral.

    I suppose that is why some "who doo" woodworkers started injecting walnut with real turquoise.

    To make it permanent. I am not a fan of that approach.

    Anything beautiful in its natural state should be left that way.

    We MF way to much in this world. Its a common practice these days.

    Yea I have milled a bit and definitely get some turquoise hues in it when it comes off the blade. Quite a bit more then what shows in your photos.

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