SCRATCH-RESISTANT

A Material is said to be scratch-resistant when its surface Hardness is such that it withstands scratches under normal use. In watchmaking, this quality mainly concerns the Crystal (watch glass) and, sometimes, the Bezel or the Case. The Sapphire crystal — synthetic corundum — is the benchmark scratch-resistant material: its hardness (9 on the Mohs scale, just after Diamond) allows it to withstand daily friction against softer surfaces. Certain technical ceramics and hard coatings (carbides, DLC (Diamond-Like Carbon)) also give a near Scratch-resistant character to External parts (case, dial, hands) components. However, some nuance is needed: “Scratch-resistant” means very resistant to scratching, not absolutely; Sapphire can be scratched or cracked by a material of equal or greater Hardness (Diamond, certain abrasives, Quartz particles). The concept is clearly distinct from stainlessness, which concerns resistance to corrosion and not Hardness. The use of Scratch-resistant Materials improves the aesthetic longevity and lasting legibility of the watch.