All you need to know about Hesalite

What’s the most underrated element of a good watch? It’s the watch glass! And today we will focus on one watch glass in particular – the famous Hesalite. This is basically another word for plexiglass or acrylic.

Believe it or not, this glass has a unique history and characteristics which makes it a popular choice. Hint: It’s even been to the moon! 

In this guide, we’ll break down everything you need to know about Hesalite – from its origins and properties to how it stacks up against Sapphire crystal. Let’s get right into it.

What’s the Deal with Hesalite?

When it comes to the world of watchmaking, few materials have become as popular as Hesalite. 

Let’s learn why this type of acrylic glass has become such a big deal. (Especially for those iconic Omega Speedmasters)

The History of Hesalite – The Omega Speedmaster

Source: Omega Chronicle

Hesalite first appeared in 1957 with the Omega Speedmaster, a watch designed for racing. But its real fame came in 1962 when astronaut Wally Schirra wore it on the Mercury Sigma 7 mission. 

Later in 1965, NASA officially approved it for all manned space flights. But getting NASA’s certification was no easy feat. Watches from a few brands faced tough tests in different environments. Only the Speedmaster made it through. It became the only watch certified by NASA.

The Speedmaster was used on the Apollo 17 mission in 1972. It also became a part of the historic handshake in space between US Commander Stafford and Russian Commander Leonov in 1975. Through it all, Hesalite protected the watch’s dial.

Omega once considered switching to sapphire crystal, but NASA preferred Hesalite to avoid shattered glass in zero gravity. And the rest is history!

What is Hesalite?

Hesalite is a type of acrylic glass, technically known as polymethyl methacrylate (PMMA). This glass has been around since the 1920s in various fields. 

However, the term ‘Hesalite’ was first coined by Omega for their Speedmaster. We have to say it sounds much cooler than plexiglass.

Main Characteristics

As compared to mineral or sapphire glass, Hesalite is much softer. This means it scratches more easily. 

But this is also its strength. This softness makes it flexible and break-resistant. Hesalite can handle impacts that might shatter other types of glass. 

Plus, small scratches can be polished away easily. It’s also non-reflective, giving you a clear view of the dial without anti-reflective coatings. This gives watches a vintage look that many love. 

And the best part of all? Hesalite is affordable and easy to replace. 

Hesalite in Daily Wear

If Hesalite can withstand the pressures on the moon, it can definitely work as your daily wear watch glass. 

Hesalite cracks rather than shatters, so a knock won’t result in tiny glass shards. It also doesn’t smudge easily, meaning fewer fingerprints to wipe off. And for Speedmaster fans, scratches are easy to remove at home.

Replacing Hesalite costs a couple of hundred dollars at Omega. Swapping out sapphire crystal is pricier because of the higher material cost and special tools needed.

What’s Sapphire Crystal?

Photo by Oka on Unsplash

Sapphire crystal is quite different from Hesalite and is fascinating to create. The process, known as the “Verneuil Process,” was invented by French chemist Auguste Victor Louis Verneuil in 1893. 

Here are some of its major characteristics:

• Sapphire crystal is incredibly scratch-resistant. Only diamonds or other sapphires can scratch it.
• It’s so clear that manufacturers can add anti-reflective coatings without blurring the view.
• Despite its clarity, sapphire crystal is more reflective than Hesalite, so it needs those anti-reflective coatings.
• Its Vickers hardness rating is around 2,000, compared to Hesalite’s 500.
• Sapphire crystals often have a milky ring around the edges, giving them a chunkier look.
• Watches with sapphire crystals are slightly heavier.
• Sapphire crystal is more expensive than Hesalite.

Sapphire crystal is popular in high-end Swiss mechanical watches and smartwatches like the Apple Watch.

Is Hesalite better than sapphire?

When comparing Hesalite and sapphire, the choice really depends on what you prioritize in a watch crystal. 

Take a look at some key comparisons:

Scratch Resistance: Sapphire is much more scratch-resistant, holding a rating of “9” on the Mohs scale, whereas Hesalite ranks between “1” and “2”.

Shatter Resistance: Hesalite is more shatter-resistant due to its plastic composition, making it less likely to break upon impact.

Affordability: Hesalite is more affordable and easier to work with. Sapphire, due to its complex creation process, is more expensive. It’s also cheaper to get a Hesalite replaced.

Readability: Both provide clear views of the watch dial. Sapphire can be highly reflective and often needs an anti-reflective coating. Hesalite offers a natural, glare-free view without additional treatment.

Sapphire Vs. Hesalite 

Ultimately, the choice between Hesalite and sapphire depends on whether you prioritize scratch resistance and a luxurious look (sapphire) or shatter resistance, affordability, and a vintage aesthetic (Hesalite). 

Why did Omega use Hesalite?

Omega offers two versions of the Speedmaster Moonwatch: one with a Hesalite crystal and another with a sapphire crystal. While the sapphire version (nicknamed the “sapphire sandwich”) features scratch-resistant sapphire on both top and bottom, there’s something romantic about collecting the Hesalite version.

Despite Hesalite being about 50 times softer than sapphire and prone to scratches, collectors can easily polish out these marks with a polishing paste. Interestingly, Hesalite is more practical for astronauts. In zero gravity, accidentally shattering a sapphire crystal could result in dangerous shards floating around, potentially being inhaled.

Hesalite, on the other hand, can absorb impact without creating hazardous fragments – though it might make telling time difficult until returning to Earth.

Moreover, the Hesalite crystal offers a clearer view of the dial and features a nice Easter egg: Omega’s logo etched into the crystal.

Thus, despite being less scratch-resistant, the Hesalite version has become the choice for purists who want the authentic Omega Speedmaster Moonwatch – the very same configuration that went to the Moon.

Hesalite Care Guide

Photo by Hans Gaber on Unsplash

We’ve mentioned that Hesalite scratches easily. Fortunately, removing these scratches isn’t too difficult. That means taking care of Hesalite crystal is much easier as compared to the more expensive Sapphire glass.

How to Remove Scratches From Watch Crystal

Do you have scratches on your Hesalite? Don’t use toothpaste—it can actually make things worse! Instead, try Polywatch. It’s a cream made specifically for Hesalite.

Just dab a little on the scratch and polish gently in a circular motion. For sapphire crystal, removing scratches is trickier and usually requires professional tools. It’s best to take it to a jeweler or watchmaker for this one.

Protecting your Watch with a Watch Winder

You’ve probably heard of a watch winder. It’s a handy gadget that houses your automatic when they’re not on your wrist.

Did you know, that keeping your watch in a winder can also protect the glass? Being super prone to scratches, Hesalite needs a safe space to rest. And a watch winder is perfect for that!

Check out Mozsly’s collection of watch winders—we’ve got some great options for watches of all aesthetics. 

FAQs

1. What does a watch glass do?

A watch glass protects the watch dial and hands from dust, moisture, and impacts. It also allows you to see the time clearly. That’s why the right watch glass has to balance clarity, reflectiveness, hardness, and scratch resistance.

2. Is Hesalite better than sapphire?

It depends on your priorities. Hesalite, being a type of acrylic, is lightweight and doesn’t shatter easily. However, it scratches more easily than sapphire. Sapphire crystal is a more popular choice for luxury watches. It’s extremely hard and highly scratch-resistant but can shatter under extreme impact. 

3. Is Hesalite the same as plexiglass?

Yes, Hesalite is a type of plexiglass. It’s made from a material called polymethyl methacrylate (PMMA). This is also known as acrylic glass. Omega calls their acrylic crystals ‘Hesalite.’

4. How easy is it to scratch Hesalite?

Yes, Hesalite glass can scratch easily, but minor scratches can often be polished out using products like Polywatch.

5. How hard is Hesalite crystal?

Hesalite crystal is relatively soft compared to sapphire. It has a lower hardness and less scratch resistance. However, this makes Hesalite more flexible and shatter-proof.