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 3 minutes

A Look at the Watch Crystal

By Donato Emilio Andrioli

Though easily overlooked (or rather, looked through),watch crystals are actually vital to the health of your watch. This watch component forms a physical barrier to protect your timepiece from dust, water, and all other particles we subject it to on a daily basis. Not only that, but watch crystals have also become a vehicle for style. Today, I’m dedicating some time to the watch crystal, and telling you what you should ideally know about it. I’ll be answering some burning questions like: What types of watch crystals are there? What are their most important properties? What crystal is used in luxury watches like those from Rolex and Omega? And last, but definitely not least: Which watch crystal comes out on top?

“Watch crystal” is a general term for the transparent layer covering a watch. The most important and most common types are mineral glass, acrylic glass, and the sapphire crystal.

Mineral Glass

In the watch world, mineral glass almost exclusively refers to tempered mineral glasses. Adding oxides such as aluminum oxide improves durability and makes the mineral glass more shock-resistant compared to normal window glass. You’ll find tempered mineral glass on affordable watches in the entry-level price segment. Seiko‘s Hardlex crystal offers a particularly scratch-resistant mineral glass thanks to a special finish. However, like all other mineral glass types, there’s one major pitfall: If mineral glass does get scratched or damaged, it’s virtually impossible to polish or otherwise remedy. This means that you either have to live with the damage or replace the glass entirely.

Mineralgläser werden gerne bei Einsteiger-Uhrenmarken eingesetzt. Seiko bietet mit ihrem Hardlexglas eine besonders kratzresistente Variante des Mineralglases.
Entry-level watch brands tend to use mineral glass. Seiko offers a particularly scratch-resistant mineral glass with their Hardlex crystal.

Acrylic Glass

Acrylic glass, or plexiglass, was the go-to material for watch crystals from the 1950s to 80s. With the rise in popularity of vintage watches, acrylic glass is also making a comeback. One especially high-profile type of plastic crystal is the Hesalite crystal. Hesalite crystal is a co-conspirator behind the striking design of the Omega Speedmaster Professional, lending the watch a special charm that still captivates watch enthusiasts in 2023. The legendary Moonwatch is still sold today with either a modern sapphire crystal or Hesalite crystal. Acrylic glasses are extremely light, relatively impact-resistant, and can be polished without much ado. Easy polishing will come in handy if your watch has acrylic glass, as its thinness makes it more susceptible to scratches. But fret not, armed with a polishing agent such as polyWatch and a soft cloth, your acrylic watch crystal will be back to its old self in no time.

Die Omega Speedmaster Professional wird auch heute noch sowohl mit Saphir-, als auch mit dem ikonischen Hesalitglas angeboten.
You can still buy the Omega Speedmaster Professional with the iconic Hesalite crystal today, or with a sapphire crystal.

Sapphire Crystal

Sapphire crystal is currently the hardest and most high-quality watch crystal on the market. It’s pretty much a given on premium luxury watches like those from Rolex and Omega. Technically, a sapphire crystal isn’t glass, and it also isn’t a real crystal either, it’s a synthetic one. Even if it can shatter if hit or dropped, with a Vickers hardness of 2000, the sapphire crystal is extremely resistant and can only be damaged by a diamond or diamond-coated tool. For comparison: mineral glass has a hardness of 800 to 950 Vickers, while the Hesalite glass on the Omega Speedmaster Professional only scores 500.

Ein Saphirglas ist bei Luxusuhren heutzutage so gut wie unabdingbar.
Luxury watches rarely come without a sapphire crystal.

What’s the best watch crystal?

When it comes to crowning a winning watch crystal, there isn’t really a blanket solution: each type has its pros and cons. Generally speaking, mineral glass will suffer fewer scratches than acrylic glass, but any you do pick up will be difficult to remedy. Acrylic glass scratches quickly, but still seduces watch fans. And if you like your watch to look like new, it can be polished to a high shine quickly, easily, and without a watchmaker. Sapphire crystals are extremely resistant to rough and tumble and are extremely hard to scratch, but it’s game over if you drop your watch or give it a nasty whack. Though if that were to happen, a shattered crystal would probably be the least of your worries. So, even though it’s not one hundred percent immune to damage and is sometimes the cause of unsightly reflections on the dial, the sapphire crystal is my favorite. It’s the best watch crystal we’ve seen to date, and there’s good reason for its omnipresence in the industry.
Interested in learning more about the parts of a watch? Here are some other articles to check out:

The Watch Bezel and What You Need to Know

About the Author

Donato Emilio Andrioli

With the purchase of my Tudor Black Bay 41, I discovered a passion for mechanical watches. I am particularly drawn to iconic watches with long and exciting histories.

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