Plexiglass/hesalite/acrylic—plastic watch crystals. They're less marketable than the more common sapphire, and on dive watches, more expensive to manufacture. So why use it on all our models?
The short answer: the marriage of romance and functionality. Plexi looks great while being able to take a beating—it's how vintage watches get their panache. So let's start there:
From left to right:
Omega Speedmaster Moonwatch (c.1967-present): As indicated by the name, the first watch on the moon.
Rolex Submariner ref. 6538 (c. 1955-1959): made famous by Sean Connery, as James Bond, in Dr. No, Goldfinger, From Russia with Love, and Thunderball.
Tudor Submariner ref. 9041/0 (c. 1975-1983): used by French Navy ("Marine Nationale") divers/combat swimmers.
Each of these icons used plastic crystals (in fact, the Omega still has the option to this day). But priorities have shifted since their era. Nowadays watches are used more as status symbols than as tools, so it makes sense that the industry would shift towards hard-to-scratch sapphire (not to mention the marketability of the word itself).
However, the difference in form and function remains. Plexi is the more transparent material. Vintage watch aficionados describe its optical quality as "warmth," because it tends to refract more than it reflects, relative to other materials, thus resulting in less glare. As such, it will tend to sparkle rather than mirror. It's also harder to smudge.
"Given the choice between acrylic or sapphire, I’ll always choose acrylic for its warmth..."
Adding to its function, plexi has a more flexible structure compared to sapphire and mineral glass, which makes it more resistant to impact. And if it does break, plexi is much more likely to crack rather than shatter, which better protects the inner components of a watch. On the downside, this flexibility means that it's easier to scratch (sapphire is the opposite; its much harder to scratch but more prone to shatter). The good news is that scratches can easily be buffed out with virtually any polishing compound.
It's that easy: scratches before and after a quick application of Polywatch.
Since we're romantic nostalgics, the choice to go with plexi was obvious, but it wasn't easy. It turns out mounting a plexi crystal on a dive watch is quite difficult and somewhat of a lost art. Most case suppliers simply couldn't do it—the material was too elastic and the watch wouldn't be very water-resistant.
It took some trial and error, but we were able to successfully adopt a mechanism known as the "armored glass" method, used by Omega in the 1950s and 60s, that deploys a steel tension ring on the crystal's inner diameter (sapphire/mineral glass only requires a plastic I-ring on the outer diameter). It's more expensive to make it this way, but to us, the cost was more than worth it.
Armored glass: using a steel tension ring (encircled) for water resistance
We love plexi because it allows us to time travel a little bit. Though it's not only a bit of nostalgia—calling back to an era of watches as instruments—plexi still looks fantastic and is still extremely practical. It's just as good now as it was back then.