Definición

• Diffusion.  A physical and chemical process whereby molecules of a substance in contact with the surface of a numismatic item penetrates into the metallic composition of the item. Of particular importance for patina finishes, diffusion is of great nuisance when certain impurities come in contact with the surface to tarnish or corrode it.  See repairs and restoration.

  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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