[Jewelry making - Article 00306] - Re: [Orchid] Sterling

[JETT Research]

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    Hey guys, I have been following this sterling/enamel thread for a few
    days now because of the metallurgical discussions and I thought I
    might throw this in the pile.  I would like to avoid the discussion
    of "is it sterling if the remaining 75 parts of the alloy is not
    copper.  In my world (USA), it certainly is sterling if there are 925
    parts pure silver.  Regardless, I design a lot of custom alloys for
    various companies for various purposes around the planet.  I got
    called to come up with one for this one company in particular.  They
    needed another deox sterling silver alloy that left less slag in the
    crucible, had fewer oxide related defects, was more tarnish resistant
    than ones currently being used, was more user friendly, yadda yadda,
    yadda...  I had done many versions of deox sterling in previous work
    so this one didn't take too long to do since I knew where I had
    screwed up before.  So I finally came up with this formula and I was
    all proud of it, standing there with my chest sticking out, when they
    blindsided me with one more requirement for this alloy.  They wanted
    to be able to oxidize it.  In my mind I was thinking, how crazy are
    these people.  They had me spend all this time developing this
    version of alloy only to want to now intentionally tarnish it. 
    Freaky!, what was the point of this exercise? 

    I have told you this story because it kind of goes along with the
    issues that I have been reading regarding enameling and sterling,
    especially from Mr. Heywood.  The solution that I came up with for
    this particular company to tarnish their new tarnish resistant
    sterling alloy might help those that are having difficulty enameling
    on tarnish resistant alloys.  The metals like Germanium, Zinc, Boron,
    etc..., are very reactive metals and are used in these types of
    alloys for that reason.  They protect the other metals in the mix
    from attack by oxygen and sulfur by sacrificing themselves first.
    Very noble.  Anyway, what I had this company do to tarnish this deox
    sterling was to pretreat it in a hot, 120 degree Fahrenheit, 20%
    Nitric acid bath for 20 seconds, rinse, and then go directly into the
    "liver of sulfur". This acid pretreatment removed the sacrificial
    elements from a few micros of the surface and left a virtually pure
    silver layer.  After oxidation, they would mechanically remove that
    pure silver layer and the higher oxidized surface back down to the
    subsurface layer that was the protective alloy. This gave them a
    jewelry item where the oxidized portion and the polished portion
    would always be the same.  This might also work for you enamel folks.
     I don't personally do any enameling but I understand the process
    and after reading some of the letters, I thought that this little
    story might be of some use.  By using tarnish resistant, low copper,
    alloys with a similar pre-treatment, you could get the high purity
    silver layer for your enamel work then polish off the outside later
    after firing.  If used properly, many deox sterlings would work well
    in this heating process since their job is to protect against fire
    scale and other evils anyway. 

    One other thing.  If the walls between the enamel areas are thick
    enough, have you tried undercutting the bezel with an inverted cone
    burr ever so slightly.   This probably would not be possible on very
    thin walls but in some other instances, it could and would help. 

Best Regards,
J. Tyler Teague
JETT Research
(Jewelry Engineering, Training, & Technology)

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