NNP

Epoxy.  A composition molded with two substances, a resin and a hardener, that sets to a very hard surface used in the coin and medal field as patterns for die reductions.

The resin has such hard and tough qualities that for most modern die cutting, an epoxy cast is satisfactory for a onetime use. In contrast to epoxy, die patterns were formerly made as electroformed copper (or even foundry cast iron), the former are still recommended over epoxy for a program where many dies are required or the die might require change and recut in the future.

While casting experience is required to make an epoxy cast (from, say, a plaster model) it is usually made in the sculpture or casting department. A positive plaster model will result in the negative epoxy cast required to cut a negative die.

Epoxy is cured at room temperature. Afterwards the epoxy can be mounted on the

die-engraving pantograph. The steel tracing point rides directly on the surface of the epoxy (thus the tough hardness is required). There is somewhat more drag on an epoxy pattern than on a copper electroform galvano, since the tracing point is steel and the epoxy is basically carbon. However, in both cases the surface of the pattern is covered with a lubricant, petroleum jelly or grease for the galvano.  A continuous supply of liquid oil is applied to the face of the epoxy as a lubricant for the stylus to ride over in transferring the modulated relief of the design.

Epoxy is resistant to acids, alkalis and solvents. However, it is not known yet how permanent it is for long term storage. (It has only been used in the coin and medal field for the last third of the 20th century.) Should it be retained it must be stored carefully, as it has a tendency to deform if not supported properly.

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