Definition

• Backdraft.  Relief on a model that is carved under a portion of the relief, an undercut; a reverse taper in which the base is under the top of the relief creating overhang. Backdraft is not reproducible in diework or in electroforming (undercuts can be cast with flexible molds made of rubber or gelatin). For a struck or cast piece to be easily released from its die or mold a draft or taper of 5° is required, to be reproduced on a pantograph 15° is required.  See bevel; undercut, undercutting.
   

  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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