[Jewelry making - Article 00025] - Re: [Orchid] Heat Patina on Copper

[Charles Lewton-Brain]

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>        Once the piece has cooled, why do the beautiful colors
>     disappear when I touch them?  It seems if I run my finger over
>     them, they vanish like magic. 

Hi Stephanie,

    Basically the reason you have the colors is a thin film which alters
    how the light reflecting to you is filtered. The thickness of the
    film changes which colors are removed, and which left. Because it is
    a thin film the moment to touch it or put oil or a sealer on it  the
    lighting conditions change and usually the surface is damaged.
    Nicholas Lacquer and Incralac are both supposed to let you keep the
    colors while still protecting them. best Charles 

    Interference colors are explained here:
    http://www.ganoksin.com/borisat/nenam/optic1.htm 

    Here is a similar coloring method. 

    http://www.ganoksin.com/borisat/nenam/iridescent-patina.htm 

    and from: http://www.ganoksin.com/borisat/nenam/cupric.htm 

    The finished product may also have some form of protective coating,
    although this patina is tough and not liable to damage if applied
    correctly. 

    Traditionally these would include waxes, vaseline and oils. Also
    available are the spray sealers and lubricants mentioned above. These
    work as water does in intensifying perceived color on the patina
    surface. The exact effect will depend upon the refractive index of
    the coating involved, its evaporation rate, viscosity, etc. One
    should make samples with various colors and different coatings for
    reference. Oils and waxes tend to darken the color. The spray
    acrylics tend to make the patina resemble green paint and I usually
    use them sprayed from a distance for a thinner more subtle effect. In
    general the use of such coatings is for aesthetic reasons rather than
    protective. 

    My favorite is clear auto enamel: intended for outdoors, intended
    for different temperature ranges, intended for metal.  Nicholson
    Lacquer (used on High School marching Band instruments) is very good. 

Charles Lewton-Brain/Brain Press
President, Canadian Crafts Federation
Box 1624, Ste M, Calgary, Alberta, T2P 2L7, Canada
http://www.brainpress.com
Tel: 403-263-3955  Fax: 403-283-9053
brainnet AT telus.net

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