Meet the Ressence Type 5, the first mechanical diver’s watch filled with oil, and quite possibly the most legible watch under water.

I don’t think I ever been this excited for a new diver’s watch! In the short few years that Ressence has been around, founder and industrial designer Benoît Mintiens has been keeping pretty busy bringing complex ideas into deceptively simple executions. With the Type 5, it goes beyond just design, bringing a very fresh (and dare i say, innovative) take on one of the most saturated watch categories.

At a first glance, the Type 5 looks inherently a lot like the independent Belgian brand’s award-winning Type 3, with its smooth pebble silhouette and instantly recognizable oil-filled dial where the hands (or disks rather) and markings are seemingly part of the crystal. But I guess that’s the whole point.

The case is made from light Grade 5 Titanium, with a slim polished central element that also makes up the lugs, a lower titanium and domed sapphire element that houses the base of the movement while also serving as a winding and time-setting crown (remember, Ressence is all about watchmaking “beyond hands”!), and sandwiched between the central case and the top sapphire dome is one of the most discrete and integrated uni-directional rotating bezels you’ll ever see. One could easily mistake it for an external minute chapter.

The entire mounted case with the dial and oil only weights 87 grams, and measures 46mm in diameter and 15.5 mm in height, which is actually quite slim for such an unorthodox diver’s watch.

Unfortunately the prototype I handled wasn’t a final production version so I can’t show the back, but if you’re familiar with the Type 3 and updated Type 1, it’s the same system where the case back is rotated to set the time and wind the mainspring, (although the movement also offers automatic winding by means of a central rotor, with a power reserve of 36 hours.

The difference with the Type 5 however is that to ensure the ISO 6425 standards of dive watches and retain a depth rating of 10 ATM or 100 meters/330 feet, the Ressence had to ensure that the case back was properly sealed, and so developed their Compression Lock System that blocks the case back from moving when in the “Lock” position in order to keep the gasket compressed. It is only relaxed when in the “Setup” mode, activated by turning one portion of the case back, the “under-bezel” if you will.

As far as I can tell, there has never been a mechanical diver’s watch filled with oil before the Ressence Type 5. Sure, instrument makers like Officine Panerai once made oil-filled diving compasses and such, but they never watches. There have been quartz-operated oil-filled diver’s watches, but that’s another story. And yet, the advantages of an oil-filled watch for diving are numerous.

First and foremost, the laws of hydraulics state that a liquid can’t be compressed, so the oil in the upper chamber of the watch compensates for underwater pressure.

And since proprietary display’s internal components are immersed in oil, they’re always lubricated. And since components are lighter when immersed in liquid, they require less energy to move.

And last but certainly not least, it offers unparalleled underwater legibility. If you’ve ever dived or even simply gone swimming with a watch on, you will have likely encountered what is known as Total Internal Reflection, where light refraction causes the watch’s crystal to behave like a mirror. So unless you’re looking at the dial straight on, you simply can’t see it.

There is a downside to using a liquid however, but thankfully Ressence found a viable solution. While the oil can’t be compressed under pressure, it’s volume (37.5ml) is affected by temperature, condensing when it’s cooled and expanding when it’s heated. To counter this affect, the watch is fitted with a system of seven small bellows that are able to compress and expand, compensating for even the slightest changes in the oil’s volume.

Now let’s get back to the hand-less dial. Made from a convex-shaped titanium, the dial features three eccentric biaxial satellites that are slightly inclined. The minutes disk is the central element, as the entire Ressence Orbital Convex System is driven by the minute axle. The hours are off-centered in an easily legible disk with Arabic numerals and baton markers. There’s a colorful thermal gauge for the oil’s temperature, and a running indicator that makes a full rotation in 90 seconds.

Besides being a very easy to read – above and below sea level, the Ressence Type 5 produces one of the most spectacular displays of photo-luminescence of any watch dial. The markers and indications are engraved and in filled with blue and green SuperLuminova.

Deeper…

I have to say, I’m really impressed with what Ressence have done. At the core of it, the concept is quite simple, and that’s to make the most legible diver’s watch around. It feels as if the work with the original oil-filled Type 3 now serves a technical purpose.

And unlike most other diver’s watches out there, the Ressence is far more adept aesthetically for “desk divers” such as myself. Sure, it’s big, but not substantial, and certainly not clunky and out of place for daily wear in any situation.

The Ressence Type 5 will be available in the coming months with a retail price of EUR 26’250 or CHF 29’00.

More information on www.ressencewatches.com