Engraving is the technique of inscribing patterns, ornamentation, numerals or letters into the movement’s parts or the watch case using various methods. Engraving can have a decorative function (motifs) or be used as a form of identification (manufacturer’s name, calibre reference number, hallmarks, etc.)
- Mechanical engraving: most of the letters and numerals on movements are engraved by CNC machine.
- Chemical etching: the surface to be engraved is covered with a UV-sensitive protective varnish. A negative of the chosen design is positioned on top of the varnish to mask those parts to be preserved. The surface is then exposed to UV rays before being dipped in an acid reagent which only erodes the exposed metal. Chemical engraving is used for extremely precise forms with lines that are several tenths of a millimetre deep.
- Pantograph engraving: the letters, numerals or forms to be engraved are inscribed on metal templates. These guide an articulated arm equipped with a cutting tool (diamond, graver or miller) which reproduces the design to the required scale.
- Laser engraving: a digitally-controlled laser beam sweeps the surface.
Modern engraving is more productive but nothing can replace the authentic touch of the engraver’s hand. Some recutting or whorls, for example, can only be done by hand. A further difference is that the artisan-engraver polishes the surface as he etches it. Machine engraving can always be finished by hand, using a sharp burin, to eliminate the unattractive mechanical aspect
The most common form of engraving is intaglio or incised engraving, where the form is cut into the metal using a burin. The engraver begins by tracing the inscription or pattern on the surface using a liner, before incising the metal. An engraver works with some twenty different burins, each of which he will have shaped to suit his own technique and hand
This is the opposite technique to intaglio as the design is created in relief by raising the metal around it. The design is traced on the front of the piece using a sharp steel liner. The relief or repoussé is formed by pushing the metal up from the back using chasing hammers and punches. The design is then smoothed and details defined using a planisher and matted to create different textures. Stamped or pressed pieces now often substitute hand-chased works. These give a clean finish and are suitable for large series but cannot be personalised.
Other decorative techniques
- Engine-turning or Guillochage: a style of hand or lathe engraving forming geometric patterns of intersecting wavy or straight lines.
- Côtes de Genève: a pattern of undulating lines, like waves, that is usually reserved for the visible surface of the bridges.
- Stippling: a pattern of close-set and sometimes overlapping concentric circles, commonly used on bridges, plates and dials.
- Openwork or skeletoning: the plates and bridges are cut away to expose the gears and reveal the beauty of the mechanism.
- Sunray brushing: a pattern of lines which intersect at the same central point to create the impression of sunrays.
- Snailing: a spiral decoration, found on oscillating weights, barrels and barrel covers.
- Circular-graining: a type of polishing or buffing comprising very fine circular lines. Usually, only the visible surface of gears are circled.
Sources: Finitions & décorations horlogères haut de gamme by Giulio Papi at www.horlogerie-suisse.com; Bevelling and finishes in top-of-the-range watchmaking at www.watches-lexic.ch; Glossary at www.hautehorlogerie.org; Tips from the Jeweler’s Bench at www.ganoksin.com. © 2009 All rights reserved