[Jewelry making - Article 00469] - Re: [Orchid] Any tricks to hiding platinum seams?

[Peter W . Rowe]

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>     I have been doing platinum work for about 15 years now and I just
>     accept the fact that you will see a seam on most work. I try to
>     use hard solder when I can. This week I was not at my shop with the
>     oxy-propane so I did a sizing with pt 1000 solder and boy did I
>     see it. 

    Yeah, you would. That's way too soft a solder for almost any sizing
    job. Remember that classic platinum solders contain little if any
    platinum (the highest melting ones, 1600 and 1700 have some platinum)
    being instead, alloys of palladium, alloyed I think, with gold or
    silver. The result is a much softer metal with a darker color. It
    mechanically is OK with platinum (though your 1000 solder is not a
    strong joint, especially for a butt joint like a sizing), but the
    color and hardness is all wrong for any sort of decent appearance. 

>     ...I then went back through the whole process and used a soft goat
>     hair brush for the final polish...........but it still showed up. 

    You might, if the original seam was really tight and well done, be
    able to burnish the seam. Sometimes this will mush around the metal
    enough so a seam doesn't show so much. Same as closing up porosity.
    But it's not the best way. 

>     I know why I see it, the metals are different hardnesses and the
>     solder 'pulls out' when polished. I am looking for a magic bullet.
>     If anyone can give it to me, i will give them my grandmothers
>     recipe for Maryland crab cakes... this means YOU MR. Binnion. 

    You can share those cakes with Jim and me both, please (grin) 

    Two methods. One is to weld the seam. Not all sizing joints can be
    done this way, but the classic weld for sizing is done by rolling a
    bit of platinum very thin, cutting a bit of this that measures
    slightly wider and longer than the width and thickness of the metal
    of the shank. Close up the seam so it's tight enough to hold this
    shim in position, so the shim fills the seam and extends out a little
    all around the seam. Using a sharp hot flame directed right at the
    shim, you'll find that platinum's poor heat conductivity means you
    can fuse that thin shim just a moment before the shank itself starts
    to melt. When it's edge melts, it continues down in a bit, welding
    the two sides of the shank. Repeat this for all four surfaces (both
    sides, inside, outside, etc.) With practice, this gives you a welded
    joint that has no seams at all. 

    The other method is suitable even for those shanks that are not
    going to be so easy to weld this way (thinner flatter shanks, or the
    like). That method is simply a better type of solder. 

    For close to ten years now, you have been able to buy a "plumb"
    platinum solder. At today's platinum prices, this stuff isn't cheap,
    of course, since a pennyweight of the solder contains not just the
    alloy constintuents, but as much platinum as your basic platinum
    itself. it comes 90 - 95 percent pure, the remainder (what lowers the
    melting point to make it a solder) is germanium and indium, if I
    recall. PMWest is the company that developed it, and it's sold by a
    number of metals dealers in addition to them. 

    The plumb solders are a bit harder to use than traditional junky
    solders. They don't flow quite as easily, and tend to sometimes leave
    a bit of a scar, the remainder of the solder piece, at the surface of
    the joint where the paillon was placed (especially with the easy
    grade). But color and hardness of the finished joint is a perfect
    match, and even if it sometimes looks like it didn't completely flow,
    in fact, it will have done so. Just put the paillon where you can
    clean up any residue afterwards. 

    The plumb solders are available in "easy", which melts around 1300,
    "medium," which melts at 1400, and "hard" which melts at 1500. I find
    the easy grade a bit difficult to use, since the solder sheet is
    often very hard and brittle, and simply cutting up bits to use is
    tricky. The medium and hard grades are more friendly that way, and
    actually flow somewhat better than the easy, though at their
    respective higher temps. I generally use the medium grade for most
    work, as it's the best color match for the 10 percent iridium
    platinum I normally work with, and it's generally suitable for almost
    all my uses. Occasionally with a complex piece I'll use the easy for
    the final assembly, but I try to avoid it, as it's just not quite as
    nice to work with. The hard grade, even though higher melting, is
    also nice to work with. Unlike gold solders, there is little
    advantage to the higher melting solders for purposes of appearance
    or strength. All three grades are "plumb", and offer similar finished
    strength and appearance. So use the stepped temperature grades only
    for when you need a difference in flow point. This differs from gold
    or silver solders where the higher melting solders also offer a
    better quality joint. 

    While I do keep the traditional platinum solders around too, at this
    point they're reserved for those repair jobs where I really need that
    low temperature solder, and this is rare, since mostly I do the
    repair jobs with the laser welder anyway. But still, it sometimes is
    still a valid choice, so long as you accept that you're soldering
    platinum with a palladium alloy that doesn't match. The real main use
    I now have for the palladium based platinum solders is much more
    understandable, and that's when I need to solder palladium itself...
    Those solders work very well for that. 

    For platinum work, though, I pretty much have totally switched to
    the plumb solders. They solve all sorts of problems. 

    PMWest's links regarding this solder:
    http://preciousmetalswest.com/platinum%20solders.php
    http://preciousmetalswest.com/developing_plumb_platinum_solder.php 

Cheers
Peter Rowe
Seattle
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