Définition

• Clouding.  The natural toning process of certain metals. White metal clouds by turning dark. Proof surface metals cloud by the formation of a frosted or hazy spot that greatly reduces the reflectiveness of the surface; this occurs fairly rapidly on bronze, much slower on silver and almost never on gold. The unnatural clouding on the surface of metals, as from cleaning or certain chemicals, is called haze.

  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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