Crystal (Glas)
The transparent disc that covers a watch's dial. Made from acrylic (plexiglass), mineral glass, or sapphire — each with different scratch resistance, impact resistance, and value implications.
A watch crystal (German Glas) is the transparent disc that covers a watch's dial. Three materials dominate modern watchmaking, each with distinct properties.
Acrylic / plexiglass
Used on most pre-1980s mechanical watches and many vintage references today. Characteristics:
- Soft. Scratches easily but the same softness makes it tolerant of impacts — it deforms rather than shatters.
- Polishable. Light scratches are removed with PolyWatch or similar plastic-polish compounds, a routine vintage-watch home task.
- Warm visual character. Domes light, generates subtle distortion, especially on highly-domed vintage chronograph crystals. Many collectors prize this look.
- Cheap to replace. A new acrylic crystal for a vintage Rolex or Omega costs €15 to €50 with watchmaker fitting.
Vintage Rolex Submariner (5512, 5513, vintage GMT, vintage Daytona) all use acrylic. Tropic-style acrylic crystals are still made.
Mineral glass
Hardened standard glass. Used in entry-level and mid-range watches in the late 20th century. Characteristics:
- Medium scratch resistance. Better than acrylic, worse than sapphire.
- Shatters under impact. Cracks and chips appear as the watch ages.
- Cheap to replace. Similar cost band to acrylic.
Mineral glass is rare in modern luxury and absent in high-end. Most contemporary mid-range Swiss watches (TAG Heuer, Tissot, lower-tier Seiko) have moved to sapphire.
Sapphire
Synthetic single-crystal sapphire (Al₂O₃). Used in essentially all modern luxury watches. Characteristics:
- Extreme scratch resistance. Mohs 9 hardness; only diamond and a few exotic abrasives can scratch sapphire in everyday use.
- Brittle. Shatters or chips under sharp impact, unlike acrylic. The damage when it occurs is more dramatic.
- More expensive to replace. A modern Rolex sapphire crystal costs €120 to €400 with service fitting. A complex sapphire (date-window, applied logo, special shape) costs more.
- Optical clarity. Anti-reflective coating is added on both faces for modern watches; vintage sapphires sometimes had AR only on the inside surface.
Why crystal type matters in dealer practice
- Vintage authenticity. A 1970s Submariner with a sapphire crystal has been retrofitted (service-replaced). The original acrylic is gone. Originality-driven collectors discount accordingly.
- Damage assessment. A chipped sapphire is a clear value reduction. A scratched acrylic is a polish-and-done item with minimal price impact.
- Cosmetics. A buyer who prefers the vintage-look will accept (and may prefer) acrylic; a buyer prioritising scratch resistance will want sapphire.
Service implications are equally split: replacing a damaged acrylic on a vintage Rolex is routine. Replacing a damaged sapphire on a modern Patek requires a manufacturer service centre and a 6 to 10 week turnaround.
Related: crown, cyclops-lens, water-resistance, polished.