Table of Contents:
- What Is Watch Glass (Crystal)?
- Acrylic Watch Crystal (Plexiglass / Hesalite)
- Mineral Watch Crystal
- Hardened Mineral Watch Crystal (e.g., Hardlex)
- Sapphire Watch Crystal
- Sapphire-Coated Mineral Watch Crystal
- Gorilla Glass / Aluminosilicate Watch Glass
- Watch Glass Types Comparison: Acrylic, Mineral, Sapphire, and More
- Which Watch Glass Type Is Best for You?
- Frequently Asked Questions
- Final Thoughts
When it comes to watches, most people focus on the dial design, case size, or movement type. But there’s one often-overlooked component that plays a huge role in both durability and aesthetics: the watch glass, also known as the crystal. Whether you're buying your first timepiece or adding to a growing collection, understanding the different types of watch glass can help you make a smarter decision.
In this guide, we’ll break down all the common (and a few not-so-common) types of watch glass, compare their strengths and weaknesses, and help you decide which one is best for your needs.
What Is Watch Glass (Crystal)?
The term "watch glass" or "crystal" refers to the transparent cover that protects the watch dial and hands. It's more than just a window—it’s your first line of defense against scratches, shattering, and daily wear.
Different materials offer varying levels of scratch resistance, clarity, weight, and cost. Let's go through each one.
1. Acrylic Watch Crystal (Plexiglass / Hesalite)
- Material: Lightweight plastic
- Production Process: Made from a polymer (PMMA), acrylic crystals are formed by heating and molding plastic sheets into shape. They are then polished for clarity and smoothness.
- Pros: Inexpensive, very shatter-resistant, can be polished to remove scratches
- Cons: Scratches easily, not as clear as other materials
- Common in: Vintage watches, affordable models, and some military designs
Fun fact: The original Omega Speedmaster Moonwatch used a type of acrylic called Hesalite for NASA missions—it doesn’t shatter in zero gravity.
Example: Swatch Twice Again on Amazon — classic design with acrylic crystal
2. Mineral Watch Crystal
- Material: Tempered glass (heat-treated)
- Production Process: Regular glass is heated and rapidly cooled to harden it, a process called tempering. This increases its scratch and shatter resistance.
- Pros: More scratch-resistant than acrylic, affordable, decent clarity
- Cons: Can still scratch, and may shatter on heavy impact
- Common in: Entry-level and mid-range watches
Mineral glass is a solid middle ground for most everyday watches. This is regular glass that’s been heat-treated to make it harder. It became the standard in many watches during the 1970s and 80s.
Example: Casio Edifice on Amazon — sporty and stylish with mineral glass
3. Hardened Mineral Watch Crystal (e.g., Hardlex)
- Material: Proprietary hardened mineral glass
- Production Process: It starts with regular mineral glass, which is then chemically or thermally treated to enhance its durability. For Hardlex, Seiko uses a proprietary thermal hardening process that strengthens the surface, improving resistance to impact and scratches.
- Pros: Tougher and more impact-resistant than standard mineral
- Cons: Still not as scratch-resistant as sapphire
- Common in: Seiko and Citizen watches
Seiko’s Hardlex is a well-known example that offers better durability for active lifestyles.
Example: Seiko 5 Automatic on Amazon — durable and affordable with Hardlex crystal
4. Sapphire Watch Crystal
- Material: Synthetic sapphire (lab-grown)
- Production Process: Synthetic sapphire is created by melting aluminum oxide at high temperatures (over 2000°C) using the Verneuil process. It’s then cut, shaped, and polished like a gemstone.
- Pros: Extremely hard (9 on Mohs scale), very scratch-resistant, excellent clarity
- Cons: More expensive, can shatter under very sharp impacts
- Common in: Luxury and high-end watches
If you hate scratches and love longevity, sapphire is the top-tier choice. Sapphire crystal is made from synthetic sapphire — the same material used in high-end camera lenses. It’s extremely hard and almost impossible to scratch.
Example: Tissot Gentleman on Amazon — sleek and durable with sapphire crystal
5. Sapphire-Coated Mineral Watch Crystal
- Material: Mineral glass with a thin sapphire coating
- Production Process: A thin layer of synthetic sapphire is vapor-deposited or fused onto a mineral glass base. This gives some of the benefits of sapphire at a lower cost.
- Pros: Better scratch resistance than plain mineral, lower cost than full sapphire
- Cons: Coating can wear off over time, less durable than pure sapphire
- Common in: Some mid-range fashion watches
This is a hybrid solution—an attempt to combine the affordability of mineral with the hardness of sapphire. This type combines a layer of sapphire with mineral glass. It offers more scratch resistance than mineral but costs less than full sapphire.
Example: Invicta Pro Diver on Amazon — rugged and stylish with sapphire-coated crystal
6. Gorilla Glass / Aluminosilicate Watch Glass
- Material: Toughened smartphone glass
- Production Process: Chemically strengthened by submerging it in a molten salt bath where smaller sodium ions are replaced with larger potassium ions. This compresses the surface, making it tough.
- Pros: Lightweight, impact-resistant, used in smartwatches
- Cons: Rare in traditional watches, may scratch more than sapphire
- Common in: Smartwatches (Apple Watch, Garmin, etc.)
Though it’s not traditional, it’s becoming more common in wearable tech thanks to its shock resistance. Originally made for smartphones, Gorilla Glass is now used in many smartwatches. It’s lightweight, tough, and resists breaking.
Example: Garmin Forerunner 55 on Amazon — lightweight and tough with Gorilla Glass protection
Watch Glass Types Comparison: Acrylic, Mineral, Sapphire, and More
| Type | Scratch Resistance | Shatter Resistance | Clarity | Price Range | Common Use |
|---|---|---|---|---|---|
| Acrylic (Hesalite) | Low | High | Medium | Low | Vintage, budget, space use |
| Mineral Crystal | Medium | Medium | Good | Low-Mid | Most budget/mid watches |
| Hardened Mineral (Hardlex) | Medium-High | Medium-High | Good | Mid | Active use (e.g., Seiko) |
| Sapphire Crystal | Very High | Medium | Excellent | High | Luxury & premium watches |
| Sapphire-Coated Mineral | Medium-High | Medium | Good | Mid | Fashion watches |
| Gorilla Glass | Medium | High | Good | Mid | Smartwatches |
Which Watch Glass Type Is Best for You?
The right choice depends on how you use your watch:
- For daily wear: Mineral or hardened mineral is a good compromise.
- For outdoor or sports use: Acrylic or Hardlex are impact-friendly.
- For style and longevity: Sapphire is unbeatable if you want clarity and scratch resistance.
- For smartwatches: You’re likely already using Gorilla Glass.
Frequently Asked Questions
Is sapphire crystal scratch-proof?
It’s extremely scratch-resistant, but not truly scratch-proof. Diamonds and very hard metals can still leave marks.
Can you polish scratches out of sapphire?
No, unlike acrylic, sapphire can’t be easily polished at home.
Can mineral or Hardlex crystals be polished?
Not really. Minor scratches may be buffed, but deep ones require replacement.
Does acrylic look cheap?
It depends. On vintage watches, it adds character. On modern pieces, it’s more of a budget-friendly compromise.
Final Thoughts
Watch glass may not be the flashiest part of your timepiece, but it plays a key role in its lifespan, appearance, and comfort. Whether you’re going for a budget-friendly field watch or a sapphire-equipped dress piece, knowing the difference can save you from future regrets—and scratches.
If you're curious about other watch components, check out our guide on types of watches and watch strap materials to complete your horological education.