In a watch, sapphires primarily serve as the crystal, the transparent cover protecting the watch dial. The use of sapphire provides exceptional durability, clarity, and a touch of luxury, enhancing the overall aesthetics and longevity of the timepiece.
Sapphire is highly valued in watchmaking for several key reasons:
- Durability and Scratch Resistance: Sapphire is one of the hardest materials known, second only to diamond. This extreme hardness makes a sapphire crystal incredibly resistant to scratches from everyday wear and tear, such as rubbing against surfaces or accidental bumps. This ensures the watch face remains clear and legible over many years.
- Clarity: Sapphire crystals offer superb optical clarity, allowing for an unobstructed view of the watch dial and its complications. This clarity contributes significantly to the watch's readability and aesthetic appeal.
- Luxury and Quality: The use of sapphire glass is often associated with higher-quality and luxury watches. Its superior properties compared to other materials like mineral glass reflect a commitment to craftsmanship and longevity.
Beyond the crystal, synthetic sapphire can also be used in other parts of a watch:
- Case Backs: Exhibition case backs made of sapphire allow wearers to view the intricate mechanical movement inside the watch without compromising water resistance or durability.
- Movement Jewels: Small, synthetic sapphire jewels (often referred to simply as "jewels") are used as bearings in mechanical watch movements. Their smooth, hard surface reduces friction between moving parts, improving accuracy and longevity by minimizing wear.
Comparing Watch Crystal Materials
While sapphire is premium, other materials exist:
| Material | Hardness (Mohs Scale) | Scratch Resistance | Clarity | Typical Use |
|---|---|---|---|---|
| Sapphire | 9 | Excellent | Excellent | Mid-range to Luxury |
| Mineral Glass | 5-6 | Moderate | Good | Entry-level |
| Acrylic (Hessalite) | 2-3 | Poor | Good | Vintage, Budget |
As the table shows, sapphire's hardness makes it the superior choice for resisting scratches, though it can be more prone to shattering on impact compared to acrylic.
In summary, sapphires in a watch primarily function as highly durable, scratch-resistant, and clear covers for the dial (the crystal), contributing significantly to the watch's longevity, legibility, and perceived quality.
