Snailing is a mechanical finishing technique that incises a succession of concentric spirals into metal, producing a pattern reminiscent of a snail shell. It's neither a coating nor electroplating: it's controlled material removal, executed with a rotating tool that advances radially across the piece. The result is a surface that captures and reflects light differently at every viewing angle.
In movement you see it mainly on wheels — barrel wheel, friction wheel, ratchet wheel — and sometimes on the plate itself. On dials it appears on chronograph subdials, on seconds counters, on minute tracks. In both contexts the function is the same: to create a visually active plane without adding thickness.
Technically snailing distinguishes itself from Côtes de Genève, which are straight parallel lines, and from perlage, which is a series of overlapping small circles used on internal surfaces invisible to the public. It also differs from sunray brushing, which is superficial radial brushing: snailing cuts, sunray rubs. On Hermès's H1912 caliber I've seen the two techniques paired on the same plate, snailing and circular graining, to give different depth to adjacent zones.
Double snailing is a variant in which the incision produces a double spiral, with a polished groove that creates contrast within the decoration itself. Aurelia Horology uses it on the ratchet wheel; Moritz Grossmann distributes snailing across three bands on the barrel wheel. It's not a casual detail: the subdivision into bands comes from the need to respect the toothed profiles and functional zones of the wheel.
From the bench I learned to distinguish hand-executed snailing from machine-made by observing the regularity of radial advance. On handmade work the pitch is never perfectly constant: there's a small variation that light reveals. On mechanized work the spiral is geometrically precise but often more shallow. Neither is necessarily superior: it depends on what the caliber wants to communicate.
The equivalent French term is escargot. In some German texts you read Schneckendekor. In Italian there is no consolidated technical term: circular lumeggiatura is an approximate translation I've never heard used in the workshop.
