In the song "Le poinçonneur des lilas" by French singer Serge gainsbourg, the mission of the Paris Metro ticket puncher is to dig holes in one ticket after another. Similarly, watchmakers need to punch holes, but this is not a stupid job. Shot-peening and graining are processes for creating specific grainy matte surfaces.
Shot-peening is the continuous spraying of countless small metal balls at high speeds in a state of full control, pounding the surface, thereby creating a residual compressive stress layer on the surface of the clock brass part and the stainless steel (or gold) case. Such craters are numerous and dense, like craters on the moon and beaches on the coast, with a uniform and symmetrical beauty. Shot peening needs to accurately control the appropriate "degree", excessive amount will damage the strength of the part, more than worth the loss. Most surface finishing processes tend to increase the brightness of the gloss, but shot peening is not the case, and the rough surface will refract the light to form a matte effect.
The Blancpain Split-Seconds Caliber 69f9 splint is shot peened and plated in rose gold for a textured texture
Graining is more complex, with hard metal or other materials abrasives grinding the surface, and the pore marks left by this process are wider, deeper and more obvious, but the process is nothing less than a "torture" for watch parts. During the process, the uniformity of the texture in terms of spacing and depth should be ensured as much as possible, and this requires a simple and precise process, especially if the graining is different from the specific polish, and it is almost impossible to make up for it if something goes wrong.
Goperfus uses frosting almost all of its movement substrates and many other components
The graining process is extremely demanding, and only a few brands can master it skillfully, and Gao Porfus is one of the best. The brand uses frosting on almost all of the movement substrates and many other components, and of course they prefer to call this process "frosting". Another one who is good at doing this in watch parts is Breguet, especially on the brand's trade series. It is sand-blasting and then coated with a ferrous metal plating layer to further enhance the matte effect.
Breguet tradition 7097 watches, the bridge and base plate are sandblasted and coated with ferrous metal plating
To ensure the authenticity of the graining process, brands have mostly continued the watchmaking traditions of the eighteenth and nineteenth centuries. These tools, of course, are not automatic, and now they seem rather primitive. With a wide surface such as a substrate, it is difficult to achieve a perfectly symmetrical matte effect even with meticulous work, even if it is meticulous. In contrast, it may be easier to create a clear effect with mechanical shot peening. In fact, whatever the solution, graining will be a complex and rare finishing process. (Photo/Text Watch House Xu Chaoyang)