[Jewelry making - Article 00008] - Re: [Orchid] Inert environment in the kiln

[James Binnion]

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Hi Giedrius,

    At this point I have made close to a thousand mokume billets and
    invested a huge amount of time and money researching the process. One
    of the biggest issues that stand in the way of a good diffusion
    bonded laminate is the presence of oxygen in the firing of the
    billet. It doesn't just affect the surface but the bulk metal as
    well, oxygen will travel great distances into the metal matrix at the
    high temperatures and long firing times used in solid state diffusion
    bonding. The least expensive method for controlling the amount of
    oxygen is to wrap the torque plate / billet assembly in a stainless
    steel foil bag filled with charcoal. The foil and charcoal work
    together to absorb and reduce most of the oxygen present in the bag
    and the gas that leaks in during the firing process. Other methods of
    inexpensively controlling the atmosphere like placing charcoal in the
    electric furnace chamber and adjusting the fuel burners and vents on
    a gas kiln for a "reducing" atmosphere are not effective enough for
    the production of a high quality billet. You can make mokume in a
    kiln or furnace that is not fully oxygen free but your weld quality
    and yield rate will be less than you can achieve with the charcoal in
    the foil bag method. Even then it is less than perfect but it is
    workable. If your billet does not come out of the furnace looking as
    clean and bright as it went in then you have oxygen presence and
    oxidation problems to a greater or lesser degree depending on how
    much oxygen got into the billet. To achieve the total lack of oxygen
    a special furnace is required. There are several types of controlled
    atmosphere furnaces and none of them are cheap. Try the stainless
    foil and charcoal method first. Once you have achieved a level of
    skill with that method then you cna decide if the costs (thousands of
    dollars) of a controlled atmosphere furnace are something you wish to
    invest in. 

Jim

James Binnion
jbin AT mokume-gane.com
James Binnion Metal Arts
http://www.mokume-gane.com
360-756-6550
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