Tuesday, December 13, 2022

How Rolex Tests Its Most Extreme Watch





“Pressure makes diamonds.”

Gen. George S. Patton 

United States Army.


The timepiece Rolex unveiled a month ago surprised the watch community and industry experts. The new Deepsea Challenge is not only the first all-titanium example offered by Rolex, but it’s also the highest depth-rated watch ever to be commercialized, having undergone pressure testing to 25% more than the deepest point on the planet. Some say it is the most extreme watch. General Patton would have called the Deepsea Challenge a great example in gemology.


Still, Rolex's announcement it had unveiled a new diver in its collection was half the story, I felt. The other half was about Rolex's ability to rate a watch to a depth very few people had ever gone. In short, how do you build and test the ultimate watch of the deep from Switzerland, a country with ski slopes and lakes?

When I reached out to Rolex and asked about the pressure tank that was built to test the new Deepsea Challenge, I noticed the tank was referred to by employees of the brand as la cuve UHP.   

Top of UHP tank has the same engravings as the watch. 

Rolex's first Ultra High Pressure tank was built ten years ago, when it tested the experimental watch that would be strapped onto James Cameron's submersible in his record-setting solo dive in 2012. When the watch came out of the tank unscathed and perfectly ticking, the Rolex watchmakers and design engineers who were involved in the project burst into applause. 

The brand updated la cuve UHP to test the highest depth-rated watch ever to be offered to the public. As it’s the case for other Rolex divers, the new Deepsea Challenge had to be tested to 25% more than the advertised rating; so, 25% more than the deepest point known on Earth. The tank had to be built big enough to accommodate more than one watch at a time to make large-scale production possible.


The tank alone is a feat of engineering worth writing about. The pressure chamber inside the UHP tank is less than 4 inches in diameter but can hold 3.5 liters of water (though less water is required for the test, Rolex told me). It can test up to 10 watches at a time, and it is completely built in grade 5 titanium to avoid any potential problems with magnetic fields.


When the tank was first developed with Comex's help, it was designed to sustain a mind-boggling pressure of 2,510 bars, or 25,100 meters of water depth. That's more than twice Mariana Trench's depth. For safety reasons, the tank was derated to 1,750 bars and equipped with an automatic relief valve. The support structure used for closing the pressure chamber can sustain a pressure of more than 100 tons when the watches are being tested, according to Rolex.


Watchmaking is all about attention to details. And so is watch testing. Rolex uses water that has been deionized when it conducts the pressure test. Deionized water, I learned, doesn't leave stains on the watch. All the testing is done at the site of Rolex world headquarters in Acacias, central Geneva. 

A Rolex representative once told me that when the brand unveils a new collection each March, it always tries to show expertise not only as a watchmaker but also as a gem-setter — from the simple floral-motif Datejust 31 to the pavé-dial rainbow Daytona. 

You could argue Rolex did it again this November with the Deepsea Challenge. The watch has undergone so much barometric testing, General Patton would have certainly called it a diamond.

Read also:

Why the Deepsea Challenge is Rolex's Moonwatch