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