[Jewelry making - Article 00793] - Re: [Orchid] Why does my gold BOIL?

[Peter W . Rowe]

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>     I use hydrogen for my torch melting. It's very clean, and you don't
>     get any embrittlement problems with super-white gold alloys. I
>     highly recommend hydrogen over acetylene. 

    Interesting, Jeffery.  Our experience was just the opposite.  Not
    that I recommend oxy acetylene for melting any precious metals.  Too
    hot.  but I've found Hydrogen to be good mostly just for platinum
    melting, or on a small scale, with the "water torches" for soldering
    operations.  We had LOTS of frustration and problems with gas
    porosity, ESPECIALLY with the super-white nickle white golds, and
    also with palladium white golds and rose golds, when we were casting
    with oxy-hydrogen.  A little less so as the flame became more
    neutral, but then it gets too hot.  When we switched to propane or
    natural gas, most of the porosity problems went away...   I've been
    told by several metallurgists that hydrogen causes problems with some
    alloys because nickle,  and copper, and perhaps some of the other
    alloying metals, tend to dissolve hydrogen when molten, and it comes
    back out of solution again when the metal solidifies, giving tiny gas
    pockets, or porosity, in much the way fine silver can dissolve lots
    of oxygen when molten, which it then spits out as it solidifies. 

Peter



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