What is a Watch Crystal

Table of Contents

A watch crystal, also referred to as a watch glass, is one of the most vital yet often overlooked components of a watch. Acting as a transparent protective cover over the watch face, the crystal safeguards the intricate dial and hands underneath while allowing the viewer to easily read the time.

Watch crystals come in various shapes, sizes, materials, treatments, and levels of durability. From affordable acrylic options to ultra-strong sapphire, watchmakers utilize different crystal types depending on the watch style, design, and intended use. The choice of crystal impacts the overall legibility, style, and functionality of a timepiece.

In this definitive guide, we will explore the ins and outs of watch crystals. You’ll learn about the most common crystal types, their characteristics and applications, how they are set into the case, and the important role they play in protecting internal watch mechanisms. We’ll also discuss custom watch manufacturing and how the right crystal choice factors into creating unique, high-quality wristwear. Let’s dive in!

Watch Crystal
Watch Crystal

Main Types of Watch Crystals

There are three major categories of crystals commonly used in modern wristwatches:

Mineral Glass

The most ubiquitous and affordable watch crystal type is mineral glass. Consisting of standard glass made from silica and other compounds, mineral crystals offer basic transparency and scratch resistance. They can be fashioned into various shapes and curvatures to fit different watch profiles.


  • Very economical option
  • Easy to produce in high volumes
  • More shatter-resistant than other materials


  • Prone to scratching/scuffing over time
  • Lacks surface hardness of more premium materials

While susceptibility to scratches is a downside, mineral watch crystals remain popular due to their low cost and versatility. They allow brands to produce quality timepieces at moderate prices, passing significant savings onto the consumer.

Sapphire Crystal

At the high end of the watch crystal spectrum is sapphire. Synthetic sapphire possesses incredible hardness and scratch resistance, second only to diamond. This makes it extremely durable and well-suited to protect watch dials and movements.


  • Extreme scratch resistance
  • Highly transparent for excellent dial visibility
  • Provides long lasting protection


  • Significantly more expensive than mineral or acrylic
  • Not shatterproof – can crack under extreme impacts

From luxury Swiss watches to extreme sport wristwear, sapphire delivers unmatched resilience and crystal clarity. Brands utilize sapphire to ensure lifelong performance and uphold premium reputations.

Plastic/Acrylic Crystals

In addition to standard mineral glass and sapphire, some watches feature plastic/acrylic crystals. Typically made from polymethyl methacrylate (PMMA), these synthetic plastic-derived crystals offer transparency and moderate durability at very affordable prices.


  • Extremely low cost production
  • Can be polished to remove minor scratches
  • Shatter-resistant


  • Soft surface prone to scratching
  • Lacks optical clarity of pricier options
  • Less durable over the long term

The low cost and unique properties of plastic/acrylic make them a viable crystal choice for very inexpensive watches where frequent replacement is expected. Their scratch resistance also lags far behind sapphire and mineral crystals.

Types of Watch Glass
Types of Watch Glass

Other Characteristics of Watch Crystals

In addition to selecting a crystal basic material – mineral glass, sapphire, or plastic/acrylic – watchmakers can utilize various treatments and production methods to achieve desired optical, mechanical, and aesthetic properties. Here are some other key attributes that differentiate crystals:


Watch crystals often feature special coatings to enhance durability, legibility, and style:

  • Anti-Reflective (AR) Coating – Multi-layer coating that prevents light reflection/glare. Improves dial visibility.
  • Scratch-Resistant Coating – Protective topping that makes crystal surface more impervious to scratches and scuffs. Provides extra hardness.
  • Colored Coatings – Tinted or metallic coatings for unique optical effects and styling. Changes crystal appearance.


The shape of a watch crystal impacts its looks and fits the overall case design:

  • Domed – Crystals with curved surfaces and raised centers to magnify dial details. Associated with more traditional styles.
  • Flat – Optically pure flat crystals with crisp modern aesthetics. Used in contemporary fashion watches.
  • Box-shaped – Boxy crystals with angled edges around a flat top. Blend vintage and modern styling.


Some crystals feature subtle magnification properties to enlarge and accentuate watch dial elements:

  • Standard non-magnifying crystals simply protect the watch face.
  • Slightly domed crystals can create a subtle magnifying lens effect, making dial details appear larger. Typically up to 1.1X magnification.
  • High domed crystals significantly amplify dial elements. Magnification up to 5X or higher.

The treatments, shaping, and magnification power described above allow watch crystal capabilities to be tailored to the exact design and functionality requirements of a timepiece.

How Crystals Are Attached

For a watch to be water and debris resistant, the crystal must form an impermeable seal with the casing. There are several methods employed to securely fit the watch glass into place:


Applying a specialized adhesive or sealant around the perimeter allows the crystal to be firmly glued in place. UV-curing glues create a rapid bond when exposed to UV light. Popular for fitting acrylic and low-cost mineral crystals.

Gasket Seal

A flexible rubber, plastic, or silicone gasket sits between the crystal and mid-case. When the crystal presses into the gasket material, its natural elasticity molds and seals against the glass edges. This method accommodates some expansion/contraction while preventing liquid ingress.

Crystal Press Fit

Press-fit crystals utilize the precision tolerances of CNC machining to create a secure interference fit between parts. The crystal underside is precision machined to perfectly match the watch bezel shape. Pressure fitting the crystal creates a snug, water-tight mechanical seal.

More expensive timepieces may combine press fitting with gaskets or o-rings for redundant water protection. The chosen attachment method impacts cost, durability, and device integrity against environmental threats like dust and water. Proper crystal mounting safeguards inner mechanisms while meeting style preferences.

Importance of Quality Crystals

As the outermost transparent barrier protecting delicate watch innards, the crystal plays a crucial role in performance, function, and styling. Here are some reasons why the quality and durability of the watch glass matters:

Protects Inner Components

The immediate purpose of a watch crystal is preventing physical impacts, dust, and moisture from damaging fragile mechanisms underneath. A robust crystal shields cogs, gears, hands, circuit boards, and other critical parts from harm.

Enhances Legibility

Scratches, scuffs, and debris on a watch face impede the ability to quickly read the time. A clear crystal sustains unobstructed dial visibility and keeps indexes, tick marks, and hands clearly discernable in all lighting.

Complements Overall Design

As part of the overall wristwatch aesthetic, the perceptual qualities of the crystal should align with intended styling. Factors like mineral vs. sapphire clarity, magnification, shape, and edge treatment contribute to harmony between form and function.

The quality, durability, and design of the watch crystal thus directly influence performance, usability, and the perception of value and attention to detail. Timepieces with robust protective coverings telegraph engineering substance beyond skin deep visuals.

Replacing a Watch Crystal

If an existing watch crystal becomes excessively scratched or damaged, replacing it can restore optics and newness. Here is the basic process:

Supplies Needed

  • New replacement crystal
  • Specialized watch press
  • Watchmaker’s screwdrivers
  • Soft surface/pad


  1. Remove watch band or straps
  2. Carefully open the watch case using screwdrivers
  3. Extract the movement mechanism
  4. Identify any gaskets or adhesive
  5. Carefully press out the old crystal using a press
  6. Clean the empty crystal cavity
  7. Apply new gaskets/adhesive if needed
  8. Align and press the new crystal into place
  9. Insert the movement and reseal caseback
  10. Reattach watch bands

While seemingly straightforward, crystal replacement requires great care, proper tools, and watchmaking know-how. For valuable or complex timepieces, it is best left to seasoned professionals.

Replace a Watch Crystal
Replace a Watch Crystal

Custom Watch Manufacturing Services

Romlicen is an experienced OEM and ODM watch manufacturer based in China. We offer professional custom services for brands seeking quality wristwear without needing to directly oversee production:

Logos and Branding

We can produce watches with your company name, logo, symbols, and other branding elements. Add unique visual identity to watch dials, bands, cases, packaging and other touchpoints.

Custom Designs

Do you have wristwatch concepts needing manufacturing expertise? We build fully custom models based on your required specifications – shapes, sizes, materials, movements, crystals, and components tailored exactly to final designs.

Watch Crystal Options

Romlicen provides expertise selecting and integrating watch crystals to match performance with budgets. Choose from our quality mineral glass, sapphire, and acrylic options backed by precise cutting, fitting, and sealing.

Through attentive craftsmanship and modern production techniques, Romlicen delivers custom OEM/ODM watches representing brands with distinction. With crystal choices being such an important wristwear decision, our knowledgeable support makes positive outcomes easy and affordable.


As we have explored, the watch crystal forms a critical transparent protective barrier between internal components and the outside elements. While often overlooked by consumers, the material properties and workmanship of the crystal directly impact the usability, durability, and perceived value of a timepiece.

Common wristwatch crystals include economical mineral glass, extremely hard sapphire, and affordable plastics/acrylics. Coatings, shaping, magnification, and specialized sealing methods allow manufacturers to tailor crystals to the exact functional and styling needs of different watches. A quality crystal not only enables clear time reading but also signifies conscientious engineering and construction.

For brands seeking custom wristwear that balances quality with affordability, Romlicen provides attentive OEM and ODM watch manufacturing services. Our expert teams manage the nuances of sourcing and integrating watch crystals to match performance goals across any price point. The result is custom branded watches representing your identity with optics and resilience to satisfy users long-term.

When you choose the material, shaping, and mounting of the watch crystal wisely, protection, enjoyment, and return on investment will persist for years of reliable timekeeping. Contact Romlicen today to explore crystal and watch customization options!

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