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Thread: What makes bronze go black?

  1. #1
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    Default What makes bronze go black?

    So my anchor winch, and some other bronze bits, have gone black. Why? It's summer here and been very hot. I'm rebuilding the deck so haven't been out for ages. The winch would be at least 25 years old has always been a typical bronze green. Until now. A cleat on the boat next door seems to be doing the same thing. My stem fitting also headed that way. Any metallurgical wisdom out there?

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  2. #2
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    Default Re: What makes bronze go black?

    sulfuric acid and salts are used to intentionally blacken architectural bronzes, brass, and copper. . .

    you could polish them and then piss on them to turn them back uniformly green
    Simpler is better, except when complicated looks really cool.

  3. #3
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    Default Re: What makes bronze go black?

    The chain goes the other way round on my windlass.
    Is every thing wackbards south of the Equator?

  4. #4
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    Default Re: What makes bronze go black?

    Around the house I use bronze wool and white vinegar ( 5% acidic acid ).

  5. #5
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    Default Re: What makes bronze go black?

    Quote Originally Posted by Paul Pless View Post
    sulfuric acid and salts are used to intentionally blacken architectural bronzes, brass, and copper. . .

    you could polish them and then piss on them to turn them back uniformly green
    So, acid rain?

  6. #6
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    Default Re: What makes bronze go black?

    Quote Originally Posted by lupussonic View Post
    So, acid rain?
    That would be my thought. Have they changed airline routing near you so you're getting more fuel dumping?

  7. #7
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    Default Re: What makes bronze go black?

    I live in the Caribbean. We have been dealing with the sargasso weed that washes ashore and then rots, letting off fumes that smell like sulphur. People who live near bays that have had this issue are experiencing blackening of fixtures in their homes. Boats have seen blackening of bronze. I think the acid rain theory is a good one unless you live near some rotting sargasso weed..

  8. #8
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    Default Re: What makes bronze go black?

    Quote Originally Posted by wizbang 13 View Post
    The chain goes the other way round on my windlass.
    Is every thing wackbards south of the Equator?
    Mine's the same way as yours, it's just Phil. Plus they go black when they wind backwards.

  9. #9
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    Default Re: What makes bronze go black?

    hydrogen sulfide
    Management is the art of counting beans. Leadership is the art of making every being count. --Joe Finch

  10. #10
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    Default Re: What makes bronze go black?

    Rotten eggs?
    Simpler is better, except when complicated looks really cool.

  11. #11
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    Default Re: What makes bronze go black?

    Quote Originally Posted by Paul Pless View Post
    Rotten eggs?
    Fart.
    Creationists aren't mad - they're possessed of demons.

  12. #12
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    Default

    Rotting seaweed then. The other side of the marina breakwater is a beach which gets huge amounts of seagrass washed up on it. Very sulphuric smell at low tide. Thanks.

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  13. #13
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    Default Re: What makes bronze go black?

    Is there anything the wooden boat forum canít cypher through?
    Simpler is better, except when complicated looks really cool.

  14. #14
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    It's great isn't it?

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  15. #15
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    Default Re: What makes bronze go black?

    I've had 3 Cape Dories with Spartan Bronze portlights, My first, a cape dory 26 suffered from the blackness on the interior only. None of the others did. When I built my current boat I sourced the same portlights. They have gone green, not black.
    lookingforward.jpg~original.jpeg
    Last edited by scottmacc; 02-09-2019 at 10:20 PM.

  16. #16
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    Default Re: What makes bronze go black?

    The portlight frames on WS went black after a winter in a Florida creek. Any solution? Nevr Dull doesn't seem to affect it.

  17. #17
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    Default Re: What makes bronze go black?

    http://nautarch.tamu.edu/CRL/conserv...ual/File12.htm
    Sometimes the black is not a sulfide, but it's hard to say what it is: Metal Plating and Patination: Cultural, technical and historical developments ~ page 75.
    https://youtu.be/L3U-8rItVmQ
    Last edited by MN Dave; 02-10-2019 at 03:02 PM.
    Management is the art of counting beans. Leadership is the art of making every being count. --Joe Finch

  18. #18
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    Default Re: What makes bronze go black?

    Quote Originally Posted by johngsandusky View Post
    The portlight frames on WS went black after a winter in a Florida creek. Any solution? Nevr Dull doesn't seem to affect it.
    acetic acid (vinegar)
    Simpler is better, except when complicated looks really cool.

  19. #19
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    Default Re: What makes bronze go black?

    Our household well water contained a lot of hydrogen sulfide and causes no end of black gung coming out of our faucets and clogging shower and fawcet heads. Installing a filtering system in the pumphouse solved the problem completely. Before that, I used a lot of "CLR" a concentrated liquid product designed to break down calcium, lime, and rust deposits. It worked quite well. I found it would remove just about any oxidation patina on yellow metal, too, especially if applied at greater strength than "the instructions on the bottle." I expect that it would quickly remove the blackened buildup on your bronze fittings like it did on my brass plumbing fixtures.


  20. #20
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    Default Re: What makes bronze go black?

    Thanks guys.

  21. #21
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    Might give CLR try. Might just leave it black. Probably not doing much harm, I just wondered what was going on.

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