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Thread: Platinum and gold - a string of questions

  1. #1
    Join Date
    Jun 2015
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    440

    Default Platinum and gold - a string of questions

    I was planning to use white gold wire to make a kind of stitching effect on gold sheet. Now I'm wondering if platinum wire might be a better option. But not knowing much about it I have a few questions:
    1. I assume platinum would be significantly more durable than white gold - is that right?
    2. Cooksons seem to sell it no thinner than 0.5mm - would it be easy enough to draw down, to say, 0.3 or 0.2mm?
    3. What do I need to be aware of when working with platinum for the first time? I've read that it's is more ductile but less malleable than gold, that it anneals at a higher temperature, that it is susceptible to cross-contamination from tools that have been used with other metals - but I have little idea of what all this might actually mean in practice...
    4. For soldering platinum to gold, what type of solder would be recommended? The platinum is 950, I believe, and the gold would be 750 red.
    5. Hallmarking: the platinum "stitches" would probably too thin to take a mark and the total quantity used would be very small in any case (ie less than the 0.5g threshold for platinum). As far as I can understand from the LAO guidance, they'd probably mark the gold part and not put any mark on or for the platinum - is this correct?

    Alan

  2. #2
    Join Date
    Dec 2014
    Location
    South Australia
    Posts
    1,844

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    Others will be able to elaborate more on this I am sure although I will pass on what I know.
    1 Yes because it is harder, also does not require plating.
    2 Don't see why not.
    3 It is less malleable, Gold is most malleable of all non alloy's, more ductile? yes it anneals at a higher temperature, also solders at higher temperature, cross contamination is a concern with all precious metals if I don't have duplicate tools I make sure to clean them between metals
    4---?
    5 Don't have this problem in Australia so I can't comment

  3. #3
    Join Date
    Jul 2009
    Location
    Romsey
    Posts
    5,256

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    It's ductile, but quite tough on tools. Drawing it down works; I like my carbide drawplates for it *but* you can also buy platinum laser welding wire which is around the 0.25mm mark IIRC.

    There's a Johnson Matthey pdf around called "An Introduction to Platinum"; it used to be available on the London Assay Office site, but I can't see it there at the moment. Well worth a read. You might find it with some googling, but I'm not sure why it has disappeared from the net virtually everywhere.

    I'd use 750 red gold solder - the mp of Pt solder is too high for your gold and the colour difference is not a problem. Actually, that's a lie - I'd laser the thing

    Some links -
    http://www.ganoksin.com/borisat/nena...um-repairs.htm
    http://www.ganoksin.com/borisat/nena...g-platinum.htm
    (Plenty of others around too)

  4. #4
    Join Date
    Jun 2015
    Posts
    440

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    Thanks, both - useful links, Peter. I think I've found the Johnson Matthey intro here - http://www.jmny.com/technical/platinum-manual

    Alan

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