Crystal

What is a Watch Crystal?

The crystal is the transparent window on the front of the watch, protecting the dial and hands from dust, moisture, and physical damage. Despite the name, most modern watch crystals contain no actual crystal — the term is inherited from an era when natural rock crystal (quartz) was sometimes used.

Types of Crystal

• Acrylic (Hesalite/Plexiglas) — used widely in watches from the 1940s through the 1980s. Lightweight and shatter-resistant, but scratches easily. Minor scratches can be polished out with a plastic polish. Still used today in some tool watches and reissues for authenticity.
• Mineral glass — harder than acrylic, more scratch-resistant, but can crack or chip on impact. Common in mid-range watches from the 1970s onward.
• Sapphire crystal — synthetic sapphire (aluminum oxide), rating 9 on the Mohs hardness scale. Highly scratch-resistant but brittle under sharp impact. Standard on quality modern watches. Can be given an anti-reflective coating on one or both surfaces.

Crystal Replacement

Crystals are typically replaced during a service if they are cracked, deeply scratched, or fogged. On vintage watches, sourcing the correct diameter and profile can require specialist suppliers. An acrylic crystal that has surface scratches but is otherwise intact can sometimes be polished rather than replaced.