[Jewelry making - Article 00150] - Re: [Orchid] Hard soldering sterling silver

[The Doctor]

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>         One of the suggestions was that I was not getting my piece hot
>     enough, and  that I needed a bigger flame.)  I adjusted my flame
>     to be 4"-5" inches long  (trying to get a bigger, softer flame),
>     and this seems to be working  better.... When I was using the
>     smaller flame, my piece would get glowing red, and the  surface
>     would sometimes shimmer like liquid.......so, if my smaller flame
>     was  getting the metal hot enough to melt (the surface, at least),
>     why was it not hot  enough to flow the solder thru the join?  The
>     solder did flow, but only  around the join, not thru it (between
>     the 2 pieces)..... 

    Your solder should flow just after the silver reaches a dull red.
    Glowing red that produces a shimmering look is too hot. You've
    actually "depletion gilded" the piece so that there is now a thin
    layer of fine silver (no longer sterling) at the surface, and that
    changes things (like soldering temperature). It also explains why
    you're getting better results with the softer flame. 

    Are you bringing all of both pieces up to soldering temperature at
    the same time? With skill and experience, you can "spot solder"
    somewhat with sterling, but you really need to concentrate on
    bringing the entire mass of both pieces up to temp simultaneously.
    Make sure you dim the lights so you can see the silver reach the
    dull red it needs to be. With too much lighting, it may look the
    right color, but it is probably too hot. 

>         I was wondering if it was because the smaller flame put the
>     hot blue cone nearer to the metal, so that the surface got
>     intensely hot, but the  whole metal mass did not?... 

    Not to put too fine a point on it, but you are the one who puts the
    flame nearer the metal, not the smaller flame, itself. Adjust your
    oxy/fuel ratio for as large a flame as you need without a hissing
    sound. This is known as a reducing (low oxygen) flame. Some call it
    a large, brushy (or bushy) flame. Sometimes with large pieces of
    silver, this isn't hot enough, and you'll have to pour on the oxygen
    a bit more. Experiment with moving the flame closer to and further
    from the metal, as some parts of the flame are hotter than others
    (another element of torch control). Flame size matters less than
    torch control, but you do need a flame large enough to bring the
    entire piece up to temperature. Torch control is a technique that is
    extremely difficult to describe. It can be demonstrated, but is best
    learned through personal experimentation, and different techniques
    are required for different soldering operations. 

    Also, a flame that is too hot, or applied for too long will burn off
    the flux and render it useless. Once you've gotten the solder to
    flow, longer exposure to the flame will raise the flow temperature
    characteristics of the solder, and it will not flow until the
    melting point of the silver. Get in, and get out quickly with your
    flame. Use a solder pick (I use titanium) to spread the solder
    across the join once it has flowed. You can't always rely on the
    solder to go exactly where you want it. If the solder doesn't flow
    shortly after the pieces reach a dull red color, chances are you'll
    have to start over: Pickle, clean, mate the join flush, firecoat,
    flux, place solder, heat. 

>         I was also wondering if maybe the firecoat helped to keep 
>     oxidation away from between the 2 pieces.......but why did'nt the
>     flux do that?.....(I am still trying to figure out why it appears
>     that there is flux  residue between the 2 pieces... 

    The firecoat does help keep oxidation from the two pieces, as well
    as cleaning them off. Also, the firecoat actually is a type of flux.
    I don't remember if you mentioned in your original post that you
    used your own self-made flux, but that could be why it didn't
    protect from oxidation. My favorite commercial flux is Prip's, which
    you may want to try. Battern's is also very good, and there are
    others. If there is flux residue actually between the two pieces,
    you haven't filed/sanded enough to mate them properly. While solder
    actually can fill SMALL gaps (it really can, despite what you've
    read) it's not easy to do, and weakens the piece. Pay close
    attention to the fit of the join you're trying to make. 

    Thanks for letting us know how you're coming along. I, for one, like
    to know if my suggestions have helped anyone. Keep it coming. 

James in SoFl

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