Perlage
The overlapping circular frosted pattern on movement plates
What it is
Perlage; also called "spotted" or "circular graining" in English, or "grenaillage" in French; is a finish applied to the hidden flat surfaces of movement plates and bridges. Each operation of the tool leaves a small circular scratch pattern; the peg is moved a fraction of a millimetre and pressed again, each new circle overlapping the previous by roughly half its diameter. The result is a matte, pearlescent field of interlocking circles covering the entire surface.
History
Perlage has been applied to movement plates in fine Swiss watches since the 18th century. Its presence under the dial; invisible during normal wear; signals a finishing standard that extends beyond what any customer will see in use. It appears on the base plates and bridges of Patek Philippe, Jaeger-LeCoultre, Vacheron Constantin, and Lange movements. The name derives from "perle" (French for pearl) because the small overlapping circles at the correct scale resemble a string of pearls. Because perlage retains oil in its recesses and slows migration away from bearing surfaces, it serves a genuine functional purpose alongside the decorative one.
How it's done
A rotating wooden or cork peg coated with an abrasive paste is pressed against the flat metal surface for a fraction of a second, leaving one circular scratch mark. The operator lifts the peg, moves it a fraction of a millimetre in a consistent grid pattern, and presses again. Each new circle overlaps the previous one by roughly half its diameter, producing the characteristic interlocking field. The pitch of the grid; and therefore the visible scale of the circles; is controlled by the craftsman's hand movement and is one of the hallmarks of a highly practiced finisher. The resulting surface is neither mirror-polished nor sand-blasted, and it retains oil between the textured ridges, slowing lubricant migration away from bearing surfaces.
In the catalog
Related
- Anglage: Beveling and polishing the edges of movement parts
- Côtes de Genève: The parallel wave-pattern decoration on bridges and rotors
- Guilloché: Engine-turned geometric engraving on metal
