Definition

• Antique Finish.  An oxidized and relieved finish giving a two-toned effect. Most often used for art medals, the process is particularly suitable for bronze or silver medals. It starts with a completely struck up, trimmed and edgelettered piece (all the steps of the pressroom completed), in the finishing department each side is abrasive blasted with
  fine particles of sand or glass beads, each one forming a microscopic cup or "tooth" for the chemical to react. Bronze or silver medals are then doused in a sulfide solution (as ammonium sulphide) that is the source of sulphur. This happens very quickly and turns the entire piece black forming a coating of copper or silver sulphide on the surface. Immersion time is critical, the longer the immersion the blacker the surface.  After rinsing to stop the action each medal is then relieved on a buffing wheel with a pumice slurry removing the blackened area on the high surfaces but retaining the black color in the crevices. This achieves the two-toned or highlighted effect. The medals are then rinsed again, dried (even baked to remove all moisture), then lacquered. This process is also called oxidized finish or french finish (the French developed it) – the terms all mean the same.  See also oxidation, finish and finishing. 

  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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