saffierglas

Saffierglas, or sapphire glass, is a transparent, highly scratch-resistant covering made from synthetic sapphire (aluminium oxide, Al2O3). It is used as a protective window in high‑end timepieces, optical devices, and various industrial components. Although called glass, it is a crystalline material and not a conventional soda-lime glass.

It is produced by crystallizing aluminum oxide into large boules using methods such as Verneuil (flame fusion), the Czochralski process, or the Kyropoulos method. The boules are cut, ground, and polished into sheets or shaped into watch crystals. Colorless sapphire is used for optical windows, while doping can create blue, pink, or other hues for specific applications.

Properties include a Mohs hardness of 9, giving high scratch resistance, good mechanical strength, and chemical stability. The material has a refractive index of approximately 1.76–1.77 and can be coated with anti-reflective films to improve optical clarity. Saffierglas is brittle and can crack or shatter under impact; it is more expensive to manufacture than conventional glass and is typically limited to certain thicknesses.

Applications are dominated by watch crystals, where sapphire covers protect the dial from scratches. It is also used as protective covers for camera lenses, smartphone sensors, and in scientific or aerospace instruments where chemical and thermal stability, as well as durability, are required. Its use in consumer electronics has varied with design choices and cost.

History of synthetic sapphire dates to 1902, when Auguste Verneuil produced the first crystals. Advances in growth techniques in the 20th century enabled broader commercial use in horology, optics, and industry.