Sapphire vs Mineral: Which Watch Glass for Your Watch?

In the watch industry, why do most luxury watches choose to use sapphire crystal glass? Is sapphire crystal glass truly a symbol of high-end watch quality?

Why do people generally believe that watches with sapphire crystal glass are of higher quality?

We aim to unravel the performance and various differences between sapphire crystal glass and mineral glass through comparative analysis, providing wise selection advice for watch enthusiasts.

We first take a look at the three most common types of watch crystal materials:

1. Sapphire Glass
2. Mineral Glass (Inorganic Glass)
3. Acrylic Glass (Organic Glass)

We’ve covered watch glass in full before:

Everything I Learned About Watches Glasses From the Watch Factory

The Differences between Sapphire Watch Glass, Mineral Glass and Acrylic Glass?

The differences between these glass materials are as follows:

Acrylic Glass

Acrylic glass, commonly known as acrylic or organic glass, is a type of material used for watch crystals. It has a softer texture and higher malleability. In the past, many watches used this material, including antique watches found in the market today.

Výhody:

• Excellent elasticity and resistant to shattering, often referred to as safety glass.

Zápory:

• Susceptible to scratching and slightly lower transparency.

Reasons for Choosing:

• Low cost, scratches can be polished by a watchmaker without the need for replacement. If scratches are too deep, the crystal can be replaced inexpensively.

Mineral Crystal Glass

Mineral crystal glass, also known as Hardlex or Acrylic Crystal, is a type of glass reinforced with minerals. It was developed due to the scarcity of natural crystals.

Výhody:

• High hardness, excellent transparency, clear and bright appearance.

Zápory:

• Higher unit price compared to Acrylic Glass.

Reasons for Choosing:

• Moderate cost, high hardness, scratch-resistant, clear and transparent with no bubbles or watermarks, and it possesses piezoelectric properties, offering special health benefits.

Sapphire Crystal Glass

Sapphire crystal glass is a crystalline surface made from artificially compressed sapphire crystals, which are aluminum oxide crystals with impurities like iron oxide and titanium oxide removed. Chemically, Acrylic Sapphire is identical to natural sapphire and does not possess a “blue” color.

Výhody:

• High density and scratch resistance, with hardness second only to diamond.
• Excellent light transmission, low friction, high temperature resistance, and superior durability compared to mineral crystal and Acrylic Glass .

Zápory:

• Not shock-resistant, vulnerable to impact, pressure, or drops, which may lead to cracks upon impact.

Which Material is Superior?

In terms of hardness and abrasion resistance: Acrylic Glass < Mineral crystal glass < Sapphire crystal glass.

Each has its advantages: Acrylic Glass is less likely to break and can be polished; mineral crystal glass has moderate scratch resistance and stronger resistance to vertical impacts than sapphire crystal glass; sapphire crystal glass, despite its high hardness, is prone to breakage and incurs higher repair costs.

For high-end customers, sapphire crystal glass is recommended due to its special physical and chemical properties, high hardness (Mohs scale 9), superior wear resistance, and resistance to corrosion.

Lower-end watches often use organic glass, also known as acrylic, which despite being prone to scratches, is resilient and widely used in low-end watches.

Each material has its advantages and is chosen based on factors such as cost, scratch resistance, transparency, and durability.

Watch Glass: Sapphire Glass VS Mineral Glass

Sapphire crystal glass and mineral glass are two common materials used in watchmaking and the production of certain optical components. Here are some key differences between them:

1. Material Composition:
   • Sapphire Crystal Glass: Made from Acrylic Sapphire, a crystalline form of aluminum oxide. It is highly transparent and scratch-resistant.
   • Mineral Glass: Composed of various minerals, typically a hardened form of glass. It is less scratch-resistant compared to sapphire crystal.
2. Hardness:
   • Sapphire Crystal Glass: One of the hardest materials（Mohs: 9), second only to diamonds ( Mohs: 10). It is highly resistant to scratches.
   • Mineral Glass: While hardened, it is not as scratch-resistant as sapphire crystal and may show signs of wear over time.

Generally speaking, sapphire crystal is three times stronger than mineral glass and 20 times stronger than plastic glass.

1. 1. Odolnosť proti poškriabaniu:
      • Sapphire Crystal Glass: Extremely resistant to scratches, making it ideal for applications where durability is crucial.
      • Mineral Glass: Can still resist scratches to some extent, but it is more prone to visible scratches compared to sapphire crystal.
   2. Clarity:
      • Sapphire Crystal Glass: Offers excellent transparency and clarity, allowing for a clear view of the dial and components underneath.
      • Mineral Glass: Generally provides good clarity but may have some distortion compared to sapphire crystal.
   3. Cost:
      • Sapphire Crystal Glass: Typically more expensive to produce, which can contribute to higher overall product costs.
      • Mineral Glass: Generally more cost-effective, making it a popular choice for more budget-friendly options.
   4. Weight:
      • Sapphire Crystal Glass: Heavier than mineral glass due to its density.
      • Mineral Glass: Lighter in comparison.
   5. Applications:
      • Sapphire Crystal Glass: Commonly used in high-end watches, camera lenses, and other applications where scratch resistance is crucial.
      • Mineral Glass: Found in a wide range of watches, eyeglasses, and other optical instruments.
   6. Shape:
      • Sapphire Crystal Glass: Sapphire crystal glass is limited to flat only.
      • Mineral Glass: Mineral crystal glass can be manufactured in a variety of forms.

Watch Glass: Sapphire Glass VS Acrylic Glass

In modern watches, the most commonly used material for the watch crystal is sapphire crystal glass. However, historically, watches have not always been made exclusively with this material as the watch crystal.

Take Rolex for example, modern Rolex watches have all switched to sapphire crystal glass, but in earlier times, before the end of the last century, Rolex also used plastic material acrylic for making the watch crystal. Acrylic material had two main advantages:

• Impact Resistance: Acrylic crystal, also known as plastic glass, is a reliable and durable material, especially resistant to impact. When tapped with a fingertip, it produces a clear and loud sound.
• Less Likely to Shatter: If an acrylic crystal breaks, it typically does not shatter into small fragments. As a result, there is almost no risk of damaging the watch dial, hands, or internal movement.

Of course, acrylic crystal is not without its drawbacks. Its biggest disadvantage is that it is not scratch-resistant and does not provide sufficient water resistance.

Acrylic material is a polymer composed of polymethyl methacrylate. In the era before sapphire crystal material became widespread, acrylic was the mainstream material used by various watch manufacturers.

The reason watchmakers favored it was because it offered a certain degree of impact resistance and protection. Even if an acrylic crystal were to break from a strong impact, it was less likely to shatter into fine particles, minimizing the impact on the watch dial.

However, acrylic crystals gradually began to be replaced because they had some noticeable drawbacks. For example, they had lower hardness and were prone to scratching, resulting in visible scratches on the crystal.

Additionally, acrylic crystals had poorer transparency, giving watches a slightly hazy appearance. Moreover, from a manufacturing perspective, plastic glass tended to be thicker, adding weight to the watch and making it less suitable for producing ultra-thin watches.

Today, well-known trendy sports watches like Casio’s G-SHOCK still use acrylic crystal glass. However, acrylic crystals have seen a resurgence in some popular sports watches today due to their impact resistance and less likelihood of shattering, and the lack of transparency does not significantly affect watches with LED screens.

Rolex gradually transitioned to technologically advanced sapphire crystal glass in the 1980s. This material is primarily composed of aluminum oxide (Al2O3), which is not a natural gemstone but rather synthetically produced. This allowed watch manufacturers to enjoy the benefits similar to natural sapphire without a significant increase in production costs.

The benefits of sapphire crystal glass lie in its high hardness, reaching a Mohs hardness of 9, which is just slightly lower than that of diamond. This means that it is not easy to scratch sapphire crystal, making it resistant to scratches.

Additionally, sapphire crystal glass has better transparency, providing a bright and clear appearance to the watch. Furthermore, it can be processed to a thinner degree, allowing for a reduction in the overall thickness of the watch.

However, these advantages do not necessarily mean that sapphire crystal glass is superior to acrylic glass. Along with its high hardness comes the risk that sapphire crystal may shatter more easily upon strong impact. In such cases, it can pose a threat to the watch dial and movement structure, especially for watches with hollowed-out or open-face designs. Therefore, while sapphire crystal glass may be highly durable, if it does shatter, the damage to the watch can be more severe.

But, Why do various brands still choose sapphire crystal material and abandon acrylic glass material?

The answer is not hard to guess. Because in daily wear, the chance of the watch being lightly scratched by external factors is greater than the chance of the watch being strongly impacted. Additionally, the technology of producing sapphire crystal glass has become very popular and does not significantly increase costs. Therefore, switching to sapphire crystal glass has become a better choice for watch factories.

Apart from these two materials, watch factories also use mineral glass to make watches, which is somewhat between acrylic glass and sapphire crystal glass. Although watches using mineral glass are not very common nowadays, they still occasionally appear in the works of some brands. However, in terms of prevalence, sapphire crystal is still the mainstream material in the watch industry.

Mineral glass is mostly used in some classic retro watches that require special crystal shapes to complement the overall style of the watch, such as single-domed and double-domed crystals. Single-domed crystals enhance the magnification effect on the dial, while double-domed crystals create a more ideal and prominent depth effect on the dial.

Whether it’s a single-domed or double-domed crystal, it adds a retro feel to the overall design of the watch, making the dial visually compelling and easy to read. This type of crystal not only achieves a three-dimensional visual effect with its convex shape but also enhances the magnification effect of the dial elements, allowing for thinner and more delicate watch designs.

Why use Mineral glass instead of Sapphire crystal glass?

This is because some watch crystals, not flat, have protruding edges that are prone to being knocked. Sapphire is also very fragile, so using regular glass is more reliable in comparison. Of course, to address the issue of scratch resistance on the crystal surface, some watch manufacturers also apply a sapphire coating to acrylic glass to achieve its scratch-resistant properties. Additionally, mineral acrylic glass is much cheaper than sapphire.

Price Comparison on Sapphire vs Mineral and Acrylic Watch Glass

Is sapphire expensive? In reality, with the widespread application of sapphire crystal glass, its market price has become very affordable. Nowadays, many popular watch brands on the market use sapphire crystal glass. However, compared to mineral glass and acrylic, sapphire crystal glass is relatively expensive.

Často

What is Mineral Watch Glass?

Mineral glass, also known as acrylic crystal, is a commonly used material in watchmaking. It is an ordinary crystal glass that undergoes polishing and hardening processes. Unlike sapphire crystal glass, mineral glass has a lower hardness. It was developed due to the scarcity of natural crystals, which couldn’t meet the demands of the industry. Its high transparency makes it suitable for various crafts, contributing to its popularity. The process of making mineral glass involves melting silica and lead oxide, resulting in a shiny surface with clarity achieved through advanced polishing technology.

Mineral-strengthened glass has a hardness of 7, making it resistant to scratches from most daily objects like knives and steel saw blades, which typically have lower hardness levels. However, it’s important to be cautious as sand grains, which also have a hardness of 7, can scratch the surface. Choosing a sapphire surface is preferable if possible. Sapphire surfaces, created by coating the glass with a layer of synthetic sapphire, offer a surface hardness of 9, making them highly resistant to scratches from anything except diamond and sapphire. Additionally, they are resistant to damage from sand grains.

Are Watches with Mineral Glass Good?

Answer 1:

Mineral crystal glass, also known as Acrylic Crystal, is a type of material used in watches. It is typically ordinary crystal glass that is polished and hardened, although its hardness is lower than that of sapphire crystal. This glass was developed due to the scarcity and difficulty in mining natural crystals, which couldn’t meet the demand. Because of its high transparency, it is popular for various crafts. Mineral crystal glass is crystalline with a high hardness (Mohs hardness of 7), good thermal conductivity, and a cool sensation when touched. It appears clear and bright against light, without small bubbles or watermarks, making it relatively expensive.

Answer 2:

The scratch resistance of mineral-strengthened glass is slightly inferior to sapphire glass, as its hardness is about 7, while sapphire glass has a hardness of 9. However, mineral-strengthened glass has higher overall compressive strength than sapphire glass. Therefore, all deep diving watches (deeper than 200 meters) use mineral-strengthened glass for their watch glass. Although sapphire glass has excellent scratch resistance, its thickness is only 5 micrometers, and its overall compressive strength is lower than that of mineral-strengthened glass, rendering it unsuitable for deep diving watches.

What is the Anti-glare Watch Glass?

In simple terms, anti-glare coating is a multi-layer film electroplated onto the lens to prevent light reflection. It’s commonly used in professional aviation, diving watches, or watches with large mirror curvature. It can be divided into double-layer anti-glare glass and single-layer anti-glare glass. The difference lies in the former being electroplated on both sides of the lens, while the latter is only coated on the inner side of the glass. The effectiveness of both types is similar.

The main function of anti-glare coating is to prevent glare and reflection, enabling better readability. When viewed from the front, it may appear as if it’s not mounted on the mirror, but from a specific angle, it reflects a layer of bluish color, similar to the eyes on the coating.

Záverečná myšlienka:

Ultimately, the choice between sapphire crystal glass, mineral glass and Acrylic glass depends on the specific requirements of the application, budget considerations, and the desired level of durability and scratch resistance. And it’s not the sapphire crystal that makes the watch better.