Definition

• Undercolor.  Either the strong base color of a medallic item to which a finish is applied providing a second color, or the hue of the first application of two intentional finishes. The undercolor must be visible after the application of the second color, which often is transparent. A bronze brown is the undercolor to which a green incrusted patina has occurred. Or in modern times, a base color applied first and a second patina applied for contrast, or to offer a subtle combination of patina colors. The intended application of two contrasting patina colors in which the undercolor is still evident is called sgraffito.
  Undercolor is not one pigment on top of another, like coats of paint. Rather it is like two colors on a plate glass, one on top surface and transparent, the other on the bottom of that glass plate. You can look through one and still see the other. In nature this occurs in the very rare case of black gold (a natural alloy of gold and bismuth). One can see the gold color but deeper down is the black hue like the black "color" of a mirror. This desirable gold and black state is impossible to create artificially.

  excerpted with permission from

  An Encyclopedia of Coin and Medal Technology

  For Artists, Makers, Collectors and Curators

  COMPILED AND WRITTEN BY D. WAYNE JOHNSON

  Roger W. Burdette, Editor

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