[Jewelry making - Article 00149] - Re: [Orchid] Polishing Platinum

[David L. Huffman]

========[ Invite a Friend - http://www.ganoksin.com/invite.htm  ]========

Hello Laura and others;

    The original post was a question about polishing platinum. Let me
    try to shed some light on this. 

    First, the issue of using separate buffs for platinum is or isn't
    relevant. Here's why. If you are going to solder platinum after
    you've been buffing it, you need to clean it thoroughly in any case.
    If all you've ever polished with a buff is platinum, then the problem
    is only about getting the polishing compounds off before you heat it.
    If you've used that buff for other metals, you especially need to get
    it clean. Other metals trapped in the surface of your platinum will
    create problems for soldering, causing pits, brittleness, and small
    explosions (no kidding). But if you're done with a piece and are
    ready to put the final polish on it, it won't matter that the buff
    has seen other metals. Again, buffs reserved for platinum only are
    the best practice, but not that critical. Cleanliness before
    soldering, as in pickling in strong nitric acid, is pretty
    important. 

    Now about polishing. 

    The best reason for buffs that are used exclusively for platinum is
    to avoid contaminating the buffs with the wrong compounds. If you use
    two different grades of polishing compound on a single buff, from the
    point at which you charge the buff with the courser of the two
    compounds, that is how course the cutting/polishing action will
    always be on that buff unless you completely clean the buff (messy
    work). 

    Platinum is dense and soft, it hangs on tools like files and
    gravers. Now polishing is really a matter of making smaller and
    smaller scratches until they are so close together light sort of
    bounces off the surface rather than lighting the topography of these
    scratches. But unlike 14K gold, which can be cut down pretty quickly
    as in file, then 320 grit, then tripoli on a felt lap, then rouge,
    platinum has to be led by the nose through a few extra steps. The
    surface smears, rather than cuts. Same happens with high karat golds,
    to a degree. Silver is somewhere in the middle. So you need to use
    several consecutively finer grades of abrasives when you sand, and
    likewise, more grades of polishing compounds when you polish. With
    platinum, you'll find that it's a lot of work to remove file marks
    with 320 grit paper, and just as much work to jump from that to 600.
    So after the filing, a little 280, then 320, then 400 (or 600 with
    more elbow grease), then ideally, a 2/0 grade of crocus or some
    equivalent to an 800 grit will work better, and you'll need to watch
    that each finer grade removes all the scratches from the previous
    grit. Some people prefer to burnish after 600, but it takes a fine
    touch and a good carbide burnisher for this to be any advantage,
    since you can chew up the surface with the burnisher while making
    nice little shiny streaks. I sometimes burnish between the 320 and
    the 400, just to pack down the surface of cast pieces (which tend to
    be slightly porous). 

    After the waltz of the sand papers, you'll need to do somewhat the
    same with abrasives. Here's the cheapskate goldsmiths route:
    something a bit courser than tripoli, like gray star or one of the
    "platinum pre-polish" compounds will get you from the 800 or 2/0 grit
    to the tripoli, but without that, it's tough to get the tripoli to
    cut out the scratches, fine as they are. Then tripoli, then rouge,
    preferably a yellow or green compound. I usually use a felt lap for
    the first two grades, then "read" it with a once over on a buff of
    the same grit, making sure I get all the scratches but not leaning
    on it enough to round off corners (as if this is much of a problem
    with platinum). No lapping with the final polish, just bring up the
    luster on a buff. 

    But the best solution is to get a set of at least 3 grades of
    polishing compound (some people like 4 grades!) that are especially
    formulated for platinum. These are a bit pricey compared to the other
    stuff. There's are pre-tripoli types, then some that are similar to
    tripoli in grade, then some that are between what you'd get with
    tripoli and what rouge would do, then the final luster compound. Most
    jewelry suppliers have compounds for platinum, and they are getting
    more reasonably priced (they used to be sold by the gram!). This way
    you'll get optimum results, and even with all the extra steps, it's
    actually easier, because here's another thing about platinum: it gets
    really hot to hold when you're polishing, especially lapping. More
    graded steps in the process mean less bearing down on the buff or
    lap, hence, less burned fingertips. And finally, if you believe the
    advertising, you can do all of this with a selection of rubber or
    silicone wheels and a foredom handpiece. Depends on the piece mostly,
    the shape of the surfaces, etc. Just expect to use at least 3 grades
    of abrasive between 800 grit and a final polish. 

    Platinum, the metal a jeweler loves to hate. It's both finicky and
    forgiving, it's expensive to the point of vulgar, but it sells
    itself because it is such a tasteful choice, it's heft is
    unmistakable, almost alien, yet with patience, it can be transformed
    into something as delicate as a butterfly, and it
    lasts....incorruptible. (Ok, platinum guild, you want to buy any of
    that plugging?). 

David L. Huffman

____________________________________________________________________
T h e   O r c h i d   L i s t
Open Electronic Forum for Jewelry Manufacturing Methods and Procedures
____________________________________________________________________
Orchid FAQ:
~ http://www.ganoksin.com/orchid/faq.htm
Orchid Archives:
~ http://www.ganoksin.com/orchid/archive
Orchid Galleries:
~ http://www.ganoksin.com/orchid/gallery.htm
Invite a Friend:
~ http://www.ganoksin.com/invite.htm
____________________________________________________________________
Tips From The Jeweler's Bench - Article Archive
~ http://www.ganoksin.com/borisat/tip_sear.htm
The Jeweler's Selected Bibliography List
~ http://www.ganoksin.com/jewelry-books
Buy Orchid Jewelry:
~ http://www.ganoksin.com/shop
____________________________________________________________________
-Unsubscribe:
-Email: orchid-request AT ganoksin.com Body=unsubscribe subject=blank
____________________________________________________________________