[Jewelry making - Article 00069] - Re: [Orchid] Overheating Yellow Gold

[James Binnion]

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    What karat yellow gold are you working with? What Alloy? How much
    cold work have you given it between anneals? You cannot just use a
    generic "anneal yellow gold at a brick red"  and hope for optimum
    results. Contact your metal supplier for correct temperatures for
    the alloys you are using. 

    Over annealing causes an enlarged grain structure that as you have
    found  results in reduced strength of the crystal matrix and can
    lead to "orange peal" surfaces or structural failure of the
    material. 

    Torch annealing is probably the worst way to anneal metal. It is a
    non uniform heat source and temperature control is basically
    nonexistent. A trained eye can only be a so so judge of temperature.
    It is very subjective and depends a lot on the ambient light
    conditions ( Light source , incandescent? florescent? sunlight? a
    combination? how bright?)  If you must anneal via torch then use a
    temperature indicating crayon or paint ( they melt at specific
    temperatures ranging from 200F to 2200F ) at least often enough to
    get and keep your eye "calibrated". 

    You will however achieve a much more through anneal if you use a
    temperature controlled kiln for your annealing and do it at a lower
    temperature for a longer period of time (15-30 min ). You will be
    amazed at how much softer and more workable your metal is if you
    kiln anneal at the right temperature for a long enough time. 

    It is also very important to put enough cold work into your metal
    before annealing. If you have not significantly reduced the
    materials section by drawing or rolling or changed its form through
    forging or raising you also run the risk of excessive crystal growth
    when you anneal just as if you annealed at too high a temperature. 

Jim

Jim Binnion

James Binnion Metal Arts
Phone (360) 756-6550
Toll Free (877) 408 7287
Fax (360) 756-2160
http://www.mokume-gane.com
jbin AT mokume-gane.com
Member of the Better Business Bureau

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