The Watch Crystal and the Crystal Clear Truth Behind Them

Have you ever stopped to think about the clear "window" on your watch? It's more than just a piece of glass; it's a vital component with a fascinating history and incredible engineering behind it. This week, we're taking a deep dive into watch crystals - those transparent shields that protect your timepiece's heart.

From Open Dials to Clear Shields: A Crystal's Journey Through Time

Before crystals, early timepieces faced a big challenge: how to protect the delicate hands and dials from dust, dirt, and accidental bumps, especially as they became smaller and more portable.

In the very beginning, large clocks often had their dials completely exposed. They were stationary and less prone to everyday knocks, so protection wasn't always a primary concern. However, as clocks became more refined, and for those that might be moved or needed extra safeguarding, watchmakers started to add coverings.

These early protective covers weren't always transparent. Often, they were rudimentary metallic covers. A prime example comes from early pocket watches, such as the famous Nuremberg Egg, where pierced brass or gilded bronze lids were fitted over the dial. These lids were frequently elaborately decorated with engravings or openwork grill designs, allowing the time to be read without fully exposing the dial. However, their function was quite limited-visibility was restricted to what could be seen through the openings, and they provided little defense against environmental elements like dust, moisture, or significant physical shock. It was protection, but at the cost of clear visibility and true environmental sealing.

The Birth of the Crystal: Portability Demands Clarity

The real push for truly transparent covers came with the rise of pocket watches. These personal timepieces were carried in pockets, handled frequently, and exposed to the elements much more than a stationary clock. The limitations of solid metallic covers became obvious - people needed to see the time instantly and clearly, without flipping open a lid.

This need naturally led to the adoption of glass as the first cover material for watches. Protective glass crystals began appearing around 1620, marking a huge step forward. These early crystals, however, were far from perfect. They were typically made from blown or flattened glass, a process that resulted in pieces that were often translucent rather than truly transparent. Imagine looking through a cloudy window - that was the challenge. They were uneven in thickness and clarity, sometimes distorting the view of the dial from certain angles. Despite these optical limitations, the motivation was clear: to offer continuous protection against dust and moisture, a vast improvement over open dials or just metal lids. This rudimentary glass laid the essential groundwork for all future innovations in watch crystal design.

As the quest for better visibility and protection evolved, watchmakers turned to rock crystal-a transparent form of quartz-as one of the earliest alternatives. This marked the birth of the term "watch crystal," rooted directly in the material itself. Although prized for its aesthetic qualities, rock crystal was relatively fragile compared to modern alternatives. It could be scratched easily, and a sharp impact might cause it to crack or shatter, limiting its practicality for long-term use-especially on everyday pocket watches.

As watchmaking techniques improved through the 18th and 19th centuries, so did the quality of glass. More precise manufacturing methods allowed for thinner, clearer, and more uniform glass, significantly improving both visibility and the overall aesthetics of watches. The ultimate test for crystals came with the transition from pocket watches to wristwatches in the early 20th century. Worn directly on the wrist, these timepieces were constantly exposed to bumps, scrapes, and knocks, making the demand for tougher, more reliable, and optically superior crystals even more critical.

       

The Modern Clear View: Types of Watch Crystal Materials and How They Came to Be

Today, watch crystals are made from three main materials, each with its own fascinating story of development, driven by the desire for enhanced durability, clarity, and affordability:

Acrylic (Plexiglass/Hesalite)

How it came to be?

In the early to mid-20th century, as industrial chemistry rapidly advanced, new synthetic polymers (plastics) were discovered. One of the most promising was polymethyl methacrylate (PMMA), independently developed by chemist Otto Röhm (at Rohm and Haas) and Imperial Chemical Industries (ICI) in the 1930s. In 1933, Otto Röhm and his team invented PLEXIGLAS, a form of PMMA, in Germany. Around the same time, British chemists Rowland Hill and John Crawford of ICI also discovered PMMA, marketing it under the trademark Perspex. This material revolutionized various industries, from aircraft canopies to signage. Watchmakers quickly recognized its potential. Glass was expensive and shattered easily, especially with the rise of mass-produced watches. Acrylic offered a lightweight, significantly more shatter-resistant, and easily moldable alternative. The primary driver was to create a cost-effective and safer crystal that wouldn't fragment dangerously upon impact, a crucial benefit for military watches and then for everyday consumer models. Early trials involved overcoming issues like potential yellowing over time or becoming brittle with age, leading to continuous refinement of the plastic compounds.

                                     

Pros of an Acrylic Watch Crystal:

• • Very Lightweight:

  Contributes to a comfortable watch feel.

• • Highly Shatter-Resistant:

  Acrylic tends to flex, deform, or crack rather than shatter into sharp pieces, making it safer.

• • Inexpensive:

  Both to manufacture and replace, which made watches more accessible.

• • "Buffable":

  Minor, superficial scratches can often be polished out with special compounds, a cherished feature for vintage watch collectors.

Cons of an Acrylic Watch Crystal:

• • Most Prone to Scratching:

  Being a soft plastic, acrylic easily picks up hairline scratches from everyday contact. Large scratches, deeper gouges, or cracks typically cannot be buffed out and require crystal replacement.

Mineral Glass

How it came to be?

Building upon traditional glass, mineral glass for watches evolved through various hardening processes. These typically involve heating the glass above its transition temperature and then rapidly cooling it, which creates a unique stress pattern where the outer surfaces are in compression and the inner part is in tension. This can also be achieved by subjecting it to a chemical bath where larger ions replace smaller ones on the surface (chemical strengthening). These processes create a compressed outer layer that significantly increases the glass's resistance to scratches and impacts compared to untreated glass. It also became a safer option as tempered glass shatters into small, rounded pieces rather than jagged shards, reducing the risk of injury.

Why they did it?

Watchmakers needed a step up from basic glass and acrylic. Mineral glass offered better scratch resistance than plastic while remaining significantly more cost-effective than the emerging synthetic sapphire, making it a common choice for many mid-range watches. The trials involved perfecting these tempering and chemical processes to ensure consistent strength, clarity, and ease of manufacturing.

Pros of a Mineral Watch Crystal:

• • More Scratch-Resistant than Acrylic:

  Considerably harder to scratch than plastic, offering improved durability for everyday wear.

• • Cost-Effective:

  Provides a good balance of enhanced durability without the premium price tag of sapphire.

Cons of a Mineral Watch Crystal:

• • Can Still Scratch or Chip:

  While tougher than acrylic, a sharp impact or contact with harder materials (like concrete, rocks, sands, and uncareful placement in drawers) can still leave a visible mark or even cause it to chip.

• • Difficult to Repair:

  Once mineral glass is scratched or chipped, it generally needs to be replaced entirely. It is possible to polish the scratch off the mineral glass crystal, but the process to do so is more complicated than polishing an acrylic watch crystal.

                           

Sapphire Crystal

How it came to be?

The journey to synthetic sapphire begins with French chemist Auguste Verneuil in the early 1900s. He developed the Verneuil method, a process to grow large, single crystals of corundum (aluminum oxide, Al2O3) in a laboratory. By melting aluminum oxide powder in a flame and allowing it to crystallize drop by drop, he could "grow" synthetic rubies and sapphires. Initially, these were valued for industrial purposes, particularly for bearings in precision instruments and watches (which often used tiny ruby bearings to reduce friction in the movement).

Why they did it?

The extraordinary hardness of synthetic corundum (sapphire) became evident. As watches became more durable and tool-oriented (like dive watches or military watches), the need for an extremely scratch-resistant crystal that could withstand harsh environments became paramount. Sapphire was the answer. Its adoption in watches in the mid-20th century was driven by the quest for ultimate longevity and resistance to daily wear. The primary trials and errors involved perfecting the Verneuil process to grow large, optical-grade, defect-free sapphire boule (a cylindrical single-structured crystal ingot), and then developing specialized diamond-tipped tools and techniques to cut, grind, and polish this incredibly hard material into precise watch crystal shapes - a challenging and costly endeavor.

                                                     

Pros of a Sapphire Crystal:

• • Unparalleled Scratch Resistance:

  This is sapphire's superstar quality. It rates a 9 on the Mohs hardness scale—second only to diamond (which is a 10). This means practically nothing in your daily life - keys, coins, sand, or even abrasive surfaces can scratch it. Your dial will remain pristine and clear for a lifetime of wear, maintaining the watch's aesthetic appeal.

• • The Best Clear Transparency:
  • • High Light Transmission: Synthetic sapphire can transmit an incredible up to 98.5% of visible light, making it one of the clearest materials known for watch crystals. This ensures your dial is always sharp, vibrant, and legible.
•  
  • • Broad Wavelength Range: It performs exceptionally well across deep ultraviolet (190 nm) to infrared (5 microns) spectrums. This broad performance ensures accurate color representation and clarity in various lighting conditions.
•  
  • • No Hazing or Yellowing: Unlike some plastics or lower-grade glasses, sapphire maintains its crystal-clear transparency indefinitely, never discolored by UV exposure or age.
•   
  • • Minimal Distortion: When properly polished and often treated with anti-reflective (AR) coatings, sapphire crystals offer a virtually distortion-free view of the dial, even when viewed at an angle.

• • Strong Chemical Resistance:

  Sapphire is highly resistant to most chemicals, acids, and solvents. This makes it an ideal choice for watches designed for harsh environments, such as industrial settings, intense diving, or rugged adventure sports, where exposure to various substances is common.

Cons of a Sapphire Crystal (and why it's still excellent):

• • Lower Shatter Resistance (relative):

  This is often cited as its main "con." Because sapphire is so incredibly hard, it's also more brittle than acrylic or even mineral glass. This means that while it's almost impossible to scratch, a very hard, direct, sharp impact (like dropping it directly onto a concrete corner or hitting it at a very specific angle) could potentially cause it to chip or shatter, whereas acrylic might only deform.

  • • However, this is often misunderstood.For most everyday impacts, sapphire's extreme hardness actually makes it incredibly resilient. A blunt force that might scratch or chip mineral glass would likely leave sapphire unscathed. Shattering requires a very specific, concentrated force that isn't typically encountered in daily wear. Its overall durability against the most common forms of watch damage (scratches) is superior, offering robust protection for your watch.

• • More Expensive:

  Sapphire is the most costly crystal to produce due to the energy-intensive process of growing and machining synthetic sapphire.

Why Brigade Watch Company Uses Sapphire Crystals?

At Brigade Watch Company, our commitment to creating durable, reliable, and aesthetically pleasing timepieces leads us to choose Sapphire Crystals as the standard for our watches. This choice is deliberate and rooted in the unmatched benefits this material provides:

Unrivaled Scratch Resistance:

We understand that watches are meant to be worn and experienced. Sapphire's extreme hardness ensures that your Brigade watch crystal will resist scratches from daily activities – from rubbing against keys in your pocket to accidental brushes against walls or rocks during an adventure. This means your dial will remain clear and pristine, maintaining its legibility and beauty for years to come.

Superior Transparency and Clarity:

We want you to appreciate every detail of your watch's dial without compromise. Sapphire's incredibly high light transmission (up to 98.5%) and broad wavelength range mean the colors and textures of your dial appear vibrant and true to life. Unlike other materials, sapphire won't haze or yellow over time, guaranteeing a consistently clear view. When combined with our anti-reflective coatings, you get a virtually distortion-free and glare-free window to your watch's heart.

               

Strong Chemical Resistance:

Our watches are built for real-world use, including challenging environments. Sapphire's inert nature means it's highly resistant to corrosion or degradation from chemicals, saltwater, fuels, and common cleaning agents. This makes Brigade watches ideally suited for industrial settings, intense diving expeditions, or rugged outdoor adventures where exposure to various substances is common.

Overall Durability and Reliability:

While some materials might boast higher "shatter resistance" in very specific, extreme scenarios, sapphire's extreme hardness means it withstands the vast majority of everyday impacts that would easily scratch or chip other materials. For the most common forms of wear and tear, sapphire offers superior protection, ensuring the longevity and reliability of your Brigade timepiece. It's a premium material chosen for premium performance.

The Art of the Curve: A History of Watch Crystal Shapes

Beyond the material, the shape of a watch crystal plays a huge role in its aesthetic, functionality, and how it interacts with the light. The evolution of crystal shapes is a fascinating interplay between available technology, practical needs, and changing design trends.

                           

Early Shapes: Flat & Functional

Initially, crystal shapes were dictated by the capabilities of early glassmaking. Making large, thick, perfectly flat pieces of glass was challenging enough. So, the earliest crystals were predominantly flat discs or simple rectangles. This was the most straightforward and cost-effective way to produce a transparent cover. Their primary purpose was simply to cover the dial, and they naturally mirrored the equally simple, often circular or rectangular, shapes of early watch cases. There wasn't much room for aesthetic experimentation; function was first.

The Rise of Curves: Aesthetics and Performance

As glass manufacturing techniques improved and watch designs became more elaborate, so did the ambition for crystal shapes. This led to the development of the distinct "profile" shapes we recognize today:

Flat:

Pros of a Flat-Shaped Watch Crystal:

• • Offers a very clean, modern aesthetic.

• • Provides a direct, unobstructed view of the dial with no optical distortion from the crystal's profile.

• • Generally the easiest and most cost-effective profile to produce.

Cons of a Flat-Shaped Watch Crystal:

• • Can be highly prone to glare and reflections if not treated with an effective anti-reflective coating.

• • Less inherent strength against direct pressure compared to a dome.

Domed/Double Domed (Curved):

How it came to be?

Early domed crystals were often a natural consequence of the manufacturing process for thicker glass, which was easier to mold into a curve than to ensure it was perfectly flat and uniform. However, the appeal of the dome quickly became intentional. Functionally, watchmakers realized a curved surface is inherently stronger against external pressure than a flat one, making it ideal for early water-resistant watches and eventually dive watches. Aesthetically, the dome adds a beautiful sense of depth and vintage character, reminiscent of the substantial early timepieces. The challenge was perfecting the curve to minimize optical distortion, leading to the development of single and eventually double-domed designs.

Pros of a Domed-Shaped Watch Crystal:

• • Creates a beautiful, vintage aesthetic that adds visual warmth and depth.

• • The curved surface is inherently stronger against external pressure, making it excellent for water resistance and robust watches.

• • Can create interesting light play and unique reflections.

Cons of a Domed-Shaped Watch Crystal:

• • A single-domed crystal can cause optical distortion, particularly around the edges of the dial, making it harder to read from extreme angles.
  • • This is solved by using double-domed crystals, which feature a domed shape both on the outer surface and underside. This design results in magnification rather than distortion.
• • More complex and costly to manufacture than flat crystals.

Box (Plexi/Top Hat):

How it came to be?

The box crystal gained significant popularity, especially with the widespread use of acrylic in the mid-20th century. Acrylic's moldability allowed manufacturers to easily create crystals with tall, vertical sides that stood proud of the watch case. This design was chosen primarily for its distinctive vintage aesthetic – it evokes the look of much older, often thicker, glass crystals that were set high on the watch. It creates a unique "picture frame" effect, drawing the eye into the dial. While visually striking, watchmakers were aware of its vulnerability, which is why it was so often paired with buffable acrylic, allowing for easy repair of scratches on its exposed sides.

Pros of a Box-Shaped Watch Crystal:

• • Offers the most pronounced vintage feel, creating a distinct "picture frame" effect around the dial where the crystal stands tall from the case.

• • This dramatic elevation is very aesthetically pleasing to many.

Cons of a Box-Shaped Watch Crystal:

• • The tall, exposed sides are very susceptible to direct impacts and scratches.

• • While often made of acrylic (which can be buffed), its height makes it more prone to incidental contact.

• • Can be prone to reflections due to its many surfaces.

Beyond Profile: The Perimeter Shapes

Alongside these distinct profiles, crystals are manufactured to match the perimeter of the watch case, which can be:

• • Round:

  The most common and classic perimeter shape, fitting perfectly with traditional round watch cases.

• • Rectangular/Square:

  Precisely cut to match rectangular or square cases, often found on elegant dress watches. These can have flat, gently curved, or even domed profiles.

• • Tonneau/Barrel-shaped:

  Designed to follow the unique, elongated curvature of tonneau or barrel-shaped cases. These often feature a corresponding cylindrical curve in their profile.

• • Irregular/Geometric:

  For highly distinctive or avant-garde watch designs, crystals can be custom-cut into almost any complex shape imaginable. These showcase extreme craftsmanship and are usually found on high-end or experimental timepieces, often combining unique perimeters with flat, domed, or multi-faceted profiles.

Why Brigade Watch Company Chose the Double Domed Crystal

At Brigade Watch Company, our choice of a double domed crystal profile for our watches is a deliberate fusion of functional superiority and timeless aesthetics. When combined with sapphire, it creates the ultimate watch crystal experience:

Best for Optical Clarity and Visibility:

Unlike single-domed crystals which can distort the dial from various viewing angles (making it appear warped, especially at the edges), a double-domed crystal is curved on both its top and bottom surfaces. These precisely calculated parallel curves work together to eliminate optical distortion, providing an incredibly clear, undistorted, and precise view of the dial from virtually any angle. This ensures superior legibility, allowing you to read the time accurately and appreciate every detail of the dial, even in challenging conditions.

Superior Pressure Resistance:

The domed shape is inherently stronger and more robust than a flat surface when subjected to external pressure. This is a critical advantage, especially for watches designed for diving or other high-pressure environments. The curved surface helps to distribute force evenly across the crystal, significantly enhancing the watch's water resistance and minimizing the risk of the crystal imploding under deep-water pressure. It's a shape built for resilience.

Enhanced Aesthetic Appeal and Depth:

The domed profile provides a beautiful, classic, and slightly vintage aesthetic that adds immense character and visual depth to the watch. It catches and plays with light in a unique way that flat crystals cannot, creating captivating reflections and giving the dial a more three-dimensional, inviting presence. This combines the best of traditional watch design with modern engineering.

Increased Internal Space (Subtle Benefit):

A double-domed crystal can sometimes create slightly more clearance between the hands and the crystal's underside. While not always the primary driver, this can occasionally allow for the use of slightly thicker movements or more elaborate dial textures without necessitating a significantly thicker watch case, contributing to a more balanced and refined overall design.

By meticulously selecting the double domed sapphire crystal, Brigade Watch Company ensures that our timepieces are not only incredibly robust and practical tools but also objects of exceptional beauty and clarity, designed to perform and impress in any environment.

For our intrepid Subcommander, we've chosen a striking blue synthetic sapphire crystal, perfectly complementing its ocean-ready design with its blue reflective hue at certain angles. We hope that you like and let us know your opinions.