[Jewelry making - Article 00351] - Re: [Orchid] Sparex No 2 101

[leonid surpin]

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>     There is little point in boiling the acid as warm sulphuric acid
>     or 'pH down' works well at about 40C to remove sulphide stains 

    In my shop, parts are made, polished and assembled. Working with
    polished components requires that only minimum amount of solder is
    used. Cleanup is not always possible, and frankly what is the point
    or polishing if excess of solder needs to be filed afterwards. But if
    one uses only minimum amount of solder, the solder does not bridges
    the gap if temperature of the sides of the joint is unequal. Solder
    only flows on the hotter side. It happens from time to time. 

    This effect is not apparent in normal practice because in majority
    of situation more solder is used than necessary. There are other
    reasons why joint may appear to soldered, but in reality it is not.
    It is soldered with glass which formed when flux melted and there may
    be partial metallic bondage here and there, but such a joint cannot
    carry any structural load. If this is the case, boiling it in acid
    would reveal the flaw. It works because when jewellery is boiled,
    due to thermal expansion the joint becomes larger and acid can attack
    the flux filling the joint. Warm pickle will not do the trick, at
    least not in the reasonable amount of time. 

    Otherwise, I have seen when setting would survive 3 rounds of
    polishing with steamer and ultrasonic treatment, but once the ring is
    sold, it invariably fails on the clients finger. Boiling jewellery in
    pickle and examining under magnification afterwards would prevent it
    from happening. 

Leonid Surpin.
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