Definition

• Abrasion.  The wearing away of minute layers of metal from the surface of a coin or medal. Coins abrade because of circulating, the constant banging against all manner of objects  – other coins, containers, cash register drawers – losing a very minute layer of its surface metal each time. About 1% of a copper coin's weight will abrade in two decades of normal circulation, slightly more for silver coins. Heavier coins abrade quicker than lighter coins. Despite the fact most coins are designed with a rim higher than its relief to take the brunt of abrasion, the design is affected by wear. High points are the first to abrade and this is the most important determination of condition. Medals wear less than coins, because they do not circulate, but both coins and medals abrade because of mishandling, dropping, carried as a pocket piece, wear as cabinet friction, or improper holders or containers.  See wear, condition.
  Abrasion can also occur in a die. The wearing away of design is usually observed as the lack of sharpness, as dies are usually withdrawn before any element is obliterated. An abraded die will display an extremely bright, polished-like striking surface as a result of the production wear.
   Abrasion is a process used in hand die engraving for smoothing a metal surface or removing tool marks. Chisel marks and other imperfections to a die’s surface can be made smooth by the use of abrasive tools, as Cratex (a rubber eraser-like material) or abrasive stones. See ENGRAVING, HAND ENGRAVING.
      

  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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