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Thread: Soldering silver, copper and brass

  1. #1
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    Default Soldering silver, copper and brass

    I am working on a new idea and soldered together, side-by-side, a small piece of silver sheet, copper sheet and brass sheet. The soldering (with hard silver solder) went fine but strangely after pickling I noticed copper spots on both the silver and the brass. I've never had copper spots appear like that before, why would that happen??

  2. #2
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    Are you using an aggressive pickle?
    Can't say anything about spots in general (in case they are not just firescale), but I remember that if you pickle brass in pickle for copper/silver/gold the zinc might dissolve into the pickle effectivly depletion gilding the copper.

    I saw this article, not sure how it will react to the mix of silver, copper and brass though:
    http://eirny.com/2013/06/03/removing...ass-or-bronze/

    /Andreas

  3. #3
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    Could you have contaminated your pickle? I've done it before by accidentally contaminating pickle with steel wool fibres which sets up a reaction and any free copper ions in the pickle then copper plate areas of silver. It doesn't take much in there for it to happen.

  4. #4
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    It's just the standard pickle I ordered through Cookson and the same stuff I always use, and this is a fairly fresh pot of it so I just don't know! I don't suppose it's at all possible for the copper to make it's way into the silver & brass because they were all being soldered together or is that just a crazy idea? I annealed the piece and pickled it again & polished it and the copper bits have disappeared now.

  5. #5
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    It's been a frighteningly long time since I've done physics and chemistry, but I would imagine the metals would have to get to melting point for them to physically intermix like that. It sounds like there's been some kind of chemical reaction somewhere that has deposited copper on there. Hopefully someone out there will have the answer because I'm quite intrigued now

  6. #6
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    Well this was just a practice piece and I was using hard solder so I did let it get very hot, the edges on parts of it had that look of almost melting.... I like to get bold when I'm just practicing to understand soldering better!

  7. #7
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    Quote Originally Posted by EmmaC View Post
    It's been a frighteningly long time since I've done physics and chemistry, but I would imagine the metals would have to get to melting point for them to physically intermix like that. It sounds like there's been some kind of chemical reaction somewhere that has deposited copper on there. Hopefully someone out there will have the answer because I'm quite intrigued now
    Actually, you can get intermixing at significantly lower temperatures - although the alloy band formed is *very* narrow. Theoretically it's possible to make solid-state diffusion bonded mokume gane at room temperature... Although I don't know how long it would take.

    Not sure about the silver, but whenever I anneal gilding metal (low zinc brass), the metal turns a pink colour as the zinc in the surface of the alloy is burned out. It may have some relevance.

  8. #8
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    Quote Originally Posted by ps_bond View Post
    Actually, you can get intermixing at significantly lower temperatures - although the alloy band formed is *very* narrow. Theoretically it's possible to make solid-state diffusion bonded mokume gane at room temperature... Although I don't know how long it would take.

    Not sure about the silver, but whenever I anneal gilding metal (low zinc brass), the metal turns a pink colour as the zinc in the surface of the alloy is burned out. It may have some relevance.
    I just had to go and look this up, very interesting, many thanks for the information!

  9. #9
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    Since you heated it quite a lot it might have been firescale still left after pickling, brass also consists of copper so it makes sense that any firestain would contain copper parts as well. A quick brush to remove any loose remains (well, obviously using a brass brush on brass is probably not a good idea, so use a softer one) and a renewed bath in the pickle would probably have had removed the last of it.
    At least that has worked for me on sterling pieces.

    /Andreas

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