[Jewelry making - Article 00610] - Re: [Orchid] Problems with melting furnace

[Lee Epperson]

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    The upper ring of the crucible must be heated. Just because the gage
    indicated melt temperature does not mean the ring is at the same
    temperature. The ring can be cool enough to chill the metal as it is
    poured. The tongs used to hold the crucible will also chill the ring
    slightly. 

    Use a higher temperature to melt the metal and let the unit sit for
    several minutes at the melt temperature before pouring. 

    Originally I was using scrap sterling from a bead punching process
    in my electric furnace. No matter how I cut up and bent the scrap it
    would not fill the crucible when melted. I would continually add
    scrap to the melt until the crucible was full of melted metal. This
    allowed thr upper ring to reach the melt temperature. 

    Once the metal was melted I would pour. Never had a problem with the
    metal chilling. When I switched to scrap pellets I did not have to
    continually add scrap to the melt to fill the crucible. I would pour
    as soon as the gage indicated the melt temperature was reached. The
    upper ring was not given the time to heat up sufficiently even though
    I was melting at the same temperature. I was having trouble getting
    sharp castings after I switched to the casting pellets. I would end
    up with chilled stream of metal the hanging from the crucible. 

    I now allow the melt furnace to stand for several minutes after it
    reached the melt temperature. If you pour more than one flask from a
    filled crucible you should let the crucible heat up again before
    making the second pour. If you raise the lid to look at the condition
    of the melted metal let the unit sit for several minutes before
    pouring. Raising the lid will allow the ring of the crucible to
    chill. 

    You should not need flux in a graphite crucible. If you use a
    graphite rod to stir the metal you should let the unit heat for
    several minutes before you pour. The rod will cool the metal. 

Lee Epperson
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