DLC, short for diamond-like carbon, is a black coating built up from carbon on a watch case. It belongs to a group of non-crystalline carbon materials that share some of the properties of diamond. It matters because it stays on and wears away much more slowly than a typical PVD-type coating.
How is DLC applied to a watch?
On watches, DLC is put onto the case by physical vapour deposition, or PVD. Carbon atoms are vaporised and fired at the watch. Once the carbon reaches the surface, it is cooled very fast. The result is a film that behaves like diamond in some ways. How hard that film is depends on how its carbon atoms are bonded. More sp3 bonds make it harder. More sp2 bonds make it softer. Because the coating is made of carbon, it comes only in black tones.
Not to be confused with
DLC and PVD are not the same kind of thing. PVD is not a coating. It is a way of applying one, and DLC is one coating it can apply. Calling a watch ‘PVD’ says how its coating was put on, not what the coating is. The watchmaker Hamtun says DLC usually holds up better and is tougher than PVD in everyday wear.
Where it comes from
S. Aisenberg and R. Chabot are widely credited as the first researchers in the field of diamond-like carbon. In 1971 they published a paper in the Journal of Applied Physics. It described a new ion-beam method for depositing the material. DLC is not only a watch finish. Outside watchmaking, it is used on tools such as end mills, drill bits, dies and moulds.
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