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Things to Know About Watch Crystals and Many More

Things to Know About Watch Crystals and Many More

An anti-reflective sapphire crystal offers better legibility to the dial while also improving the watch's aesthetics. Explore more here!
May 06, 2024

Awatch dial is more than just a place to display time, date, or other complications but also where the focal point of the general appearance lies. By that means, what covers a dial is very important than you think. For that, the watchmaking industry comes up with an anti-reflective sapphire crystal to protect the dial and give optimal legibility to the wearer.

The fact is not all watches come with a sapphire crystal which also contributes to why a watch is expensive. There are several other types of crystal used to protect the dial. Each comes with pros and cons that you need to consider before buying a watch. 

In addition, not all watches are equipped with anti-reflective (AR) coatings. In simple, AR coating is useful to give clear and better legibility for a time-telling experience as crystal, in its nature, is reflective. Therefore, AR coating is applied on the surface to cancel out the reflection. 

In this article, we’re going to look closer at what an anti-reflective sapphire crystal is and the benefits of using the coating. As a starter, we’ll also take a look at different types of crystals commonly used to protect the dial.

Different Types of Watch Crystals

 

As for now, there are three different types of watch crystals used in a timepiece as sapphire, mineral, and acrylic. The three materials possess different characteristics that make them used in different circumstances as well. Below are the details for each crystal.

Sapphire Crystal

The most renowned watch crustal is sapphire which is known for its quality and hardiness. It is mostly associated with the premium end of timepieces available on the market. 

What is a sapphire watch crystal, exactly? The sapphire watch crystal is generally made not from the commonly known sapphire but from man-made sapphire. 

These come in the form of a transparent crystallized Aluminum oxide constructed in laboratories. The result is a hardy and beautiful scratch-resistant finish. 

Moreover, the sapphire watch crystal ranks an incredible 9 out of 10 on the Mohs hardness scale.

Mineral Crystal

Alternatively known as hardlex, the mineral crystal is popularly known for its affordability and is equipped in many entry-level and affordable watch brands

A mineral watch crystal is made from silica. One notes that the glass is not as distinctive as the usual glass used for windows at home.

This watch crystal type is evidently more resistant to scratches as opposed to acrylic crystals albeit less reflective than its sapphire counterpart. 

But, this crystal watch type does offer enough impact resistance although limited in quality for the everyday timepiece. This glass ranks a 5 out of 10 on the Mohs hardness scale.

Acrylic Crystal

Third, the acrylic watch crystal otherwise known as perspex, hesalite, or plexiglass is made from a specialized form of plastic known as polymethyl methacrylate. These crystals are built to contour on top of the dial.

The use of acrylic watch crystal type can be tracked in retro-inspired timepieces due to the flexibility to be manipulated and to easily form the domed glass offering a unique distortion when viewed from an angle. 

Alternatively, this type is also fitted to low-cost watches contributed by the materials’ inexpensive retail price. Back in the past, many watches used hesalite crystals. No wonder, you can find all vintage watches in this type of watch crystal. 

Read also: Hesalite vs. Sapphire: Comparing Crystal of Omega Moonwatch

What is Anti-Reflective Coating?

As the name suggests, an anti-reflective coating is a layer applied on a lens of any kind, including the watch crystal. In another example, AR coating is also used in camera lenses to make them versatile in various lighting conditions.

Steinhart Ocean One Titanium 500 GMT Premium
Steinhart Ocean One Titanium 500 GMT Premium

In the watchmaking industry, the watchmakers will use a technique known as the PVD (physical vapor deposition) method to apply the substance. The main idea of the application is to improve legibility when reading the time on the dial. At the same time, the AR coating also tries to not compromise the clarity of the crystal.

What is Anti-Reflective Sapphire Crystal?

Now that you know what AR coating is, let’s move on to how it is applied to sapphire watch crystal. The anti-reflective sapphire crystal has become increasingly popular in recent years thanks to its legibility performance and the clarity to show the delicacy of the dial.

Before understanding what an anti-reflective sapphire crystal is, let’s start with the sapphire first. Sapphire is a gemstone that is known for its durability and scratch resistance. It is one of the hardest materials in the world, and it is also very transparent. 

Steinhart Ocean One Titanium 500 GMT Premium with double anti-reflective domed sapphire crystal

That makes it an ideal material for a watch crystal, as it can protect the dial from scratches and damage while still allowing the wearer to easily read the time. However, one of the downsides of the sapphire crystal is that it can be quite reflective.

That can make it difficult to read the time in bright light or direct sunlight, as the reflection can obscure the dial and hinder the wearer to tell the time. To overcome this issue, watchmakers have developed anti-reflective coatings for a sapphire crystal.

Anti-reflective sapphire crystals are designed to reduce the amount of reflection that is visible on the surface of a material. They work by using multiple layers of material that have different refractive indexes. These layers are arranged in a specific pattern designed to cancel out the reflection, making the material appear more transparent.

In this case, the coating can reduce the amount of reflection on the surface by up to 99%. This means that the watch face is much easier to read in bright light or direct sunlight.

Read also: Everything You Need to Know About Super-LumiNova Watches

Things to Consider About Anti-Reflective Sapphire Crystal

However, anti-reflective sapphire crystal still has several things to pay attention to. There are some factors that can affect the effectiveness of an AR coating on the sapphire crystal. 

One of the most important is the thickness of the coating. A thicker coating will generally be more effective at reducing reflection, but it can also be more prone to scratching or damage.

Another factor to consider is the angle of the light hitting the crystal. AR coatings are most effective when the light is hitting the surface at a perpendicular angle. If the light is hitting the crystal at an angle, some reflection may still be visible.

Advantages of Using Anti-Reflective Sapphire Crystal

Looking at the explanation above, you might have noticed that AR coating is useful to reduce reflections and increase the watch’s legibility. Below is the advantage in detail.

Improved Legibility

The use of an anti-reflective coating in a sapphire crystal can greatly improve the legibility of the dial. This is particularly important for watches designed for outdoor activities, such as diving or hiking. 

In these situations, it is crucial that the wearer can quickly and easily read the time, and an AR coating can help to achieve this. 

Improve the Watch Aesthetics

Believe it or not, having a timepiece that cancels out reflections bring distinctive charm as the whole appearance on the dial can be clearly seen. 

Without an AR coating, the reflection on the surface of the crystal can detract from the design of the watch. That said, by reducing this reflection, the watch face appears clearer and more visually appealing.

Wrap Up!

An anti-reflective sapphire crystal is a valuable part of a timepiece. It can greatly improve the legibility of the watch dial, while also enhancing the overall aesthetic of the watch. As such, no wonder that watches with sapphire crystal and applied with AR coatings come at a more expensive price.

You might also like: A Dandy Manual on Understanding Sapphire Crystal in Watches

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