Good-quality, light-colored dials were often made by chemical deposition of a fine layer of pure silver onto a brass plate. By tweaking the coarseness of the grain given to the underlying plate, coupled with the high purity of the silver layer, the surface could be rendered almost pure white.
Sometimes a silvery tint was preferred, and other times an almost creamy effect could be achieved — think of the subtle range of silvery tints of Cartier dials, and you’ll have a good idea about what I mean. The same method was used with good-quality old watches like 1960s Patek Philippes, some early Rolexes (particularly the original Prince models) and Vacheron Constantins.
Who knows what beautiful untouched sliver lies below this sun-distressed lacquer?
Protection from Oxidation
In these high-grade dials, the markings were engraved rather than printed, and filled with fired enamel, then silvered as described above. The problem with this is that the white surface could easily fall victim to the discoloration of sulphur in the atmosphere, along with tarnishing copper molecules that migrate to the surface from the underlying brass beneath.
To protect the white surface from this oxidation (making them brown or black), they would be lacquered with cellulose lacquer. Like an “old master” painting, this lacquer coating is considered to be sacrificial, to be occasionally washed away in a solvent and reapplied as necessary, leaving the pure surface of the dial untouched beneath.
However, cellulose lacquer itself is quite prone to yellowing with age, and this is exacerbated by the ingress of moisture, including atmospheric humidity. All this leads, eventually, to a dial that has all the appeal and charm of a nicotine-stained wall in an East London pub.
Silver dials are not the only ones prone to this premature ageing. Dials are often colored metallic blue, green or other shades — usually achieved by electroplating. These surfaces are incredibly fragile — out, again, comes the lacquer, and with it the built-in time limit on good looks.
The Making of Dark-Colored Dials
On the other hand, dials in opaque colors, including those of vintage black dials that have turned tropical, are usually made by an entirely different process. The main color is literally painted on.
Each dial blank is mounted face up, and spun while a single blob of the desired paint is dripped onto it. The liquid spreads out into a perfect, wrinkle- and bubble-free film, a beautiful limpid surface.
After heat-curing, any remaining meniscus at the edge is cut away, leaving a flat plane of a single color that can be printed onto, have batons and details attached, subdials let in, etc.