Sapphire glass for luxury watches: What you need to know about it

Anyone who deals intensively with luxury watches will definitely have come into contact with sapphire crystal. It has high mechanical strength, thermal stability, and is considered extremely scratch-resistant. There are hardly better conditions for preserving a high-quality wristwatch. But what exactly is sapphire crystal and how is it made?

Watch enthusiasts and collectors have most likely already encountered sapphire crystal in the past. High-quality processed luxury watches from well-known brands often feature a watch crystal made of sapphire crystal, and selected models even have a case back made from this material.

Properties of sapphire crystal

Why do so many brands rely on sapphire crystal? This is mainly due to the positive properties that sapphire crystal combines. Equipped with high mechanical strength, high thermal stability, chemically neutral, extremely scratch-resistant, and non-porous, sapphire crystal is perfect for manufacturing luxury watches and preserving optical quality over decades.

In terms of hardness, sapphire crystal has 1800 to 2200 Vickers. In comparison, stainless steel only reaches about 200 Vickers.

What is sapphire crystal?

Contrary to what the name suggests, sapphire crystal is by no means glass nor does it have anything to do with the gemstone "sapphire", famous for its blue color. There is one similarity, however, since the gemstone "sapphire" is a type of corundum. Sapphire crystal is made of white corundum, which is synthetically produced. It is an exact replica of natural corundum in terms of chemical composition and properties.

Red corundum, the basis of the legendary ruby, is also synthetically produced to manufacture inexpensive jewels for the Movement.

Two different processes can be used to manufacture sapphire crystal. Either the Verneuil process (named after Professor Auguste Verneuil) or the EFG process (edge-defined film-fed growth). Both processes require high specialization and special manufacturing, from which watch crystals for the most renowned brands are created.