VOCABULARY TERM: ENGRAVING MASTER

Engraving Master. A metal pattern usually made by acid etching which serves as a template for engraving a design a metal object as a medal or plate by a pantographically on controlled surface engraving machine (see Gorton). An engraving master is required for a design other than letters (which can be engraved from stock template letters) – including monograms, signatures, logos and other nonletter designs. Engraving masters are made of metal, as copper, or any hard etchable material, even some plastics. The design is usually oversize, having been pantographically enlarged from original copy, it is incuse design as the channel in the master is what guides the tracer point to effect the engraving.

How engraving masters are made. From original black-and-white copy, as a drawing, signature or pasted-up mechanical, a film negative is shot, at which time the image is usually enlarged to perhaps two or more times original size. If necessary the film image is retouched – open spots in black areas are stripped in (with red stripping fluid) – unintended spots on clear film is scrapped off with a blade.

This film negative is then placed against an emulsion-coated metal plate (called a flat) and exposed to an arc light that transfers the image to the metal plate. Additional chemical coating makes the negative area impervious to acid etching; the positive area can then be acid etched. The depth of the etch is about .0040 (forty-thousandths of an inch). After the plate is cleaned and washed it is ready for use.

How an engraving master is used. The engraving master is mounted on the copy platform and locked in place in a tracer-controlled engraving machine. A tracing point is positioned in the channel at some outer point (it is not necessary to start in the center or at the upper left and move from left to right) – the operator may start at any outer position, checking his setting that the reduction ratio will permit the entire design to fit within the space intended on the object to be engraved. Some operators will make a full sample cutting in a clear plastic or Lucite; this is then laid over the intended object to insure the full design will fit the allowed space and it is positioned where intended (if not, the ratio is corrected).

The arm with the tracing point controls – in ratio and proportion – the arm with the cutting point. All design therefore is pantographically reproduced from incuse area of the engraving master to engraved design on the final metal surface.

To read the complete entry on the Newman Numismatic Portal, see:
Engraving Master (https://nnp.wustl.edu/library/dictionarydetail/515856)

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