Ever since I got into watches many years ago, I developed a somewhat obsession with dive watches. I love their robustness and versatility, and the fact that hundreds of variations have been made since the first diver was released in the 1950s. When recreational diving became popular in the 1960s/70s, people wanted to have a decent watch to dive with but were not particularly interested in the larger and thicker professional divers in the likes of the Rolex Submariner, the Blancpain Fifty Fathoms, and the Doxa Subs. So, watch brands started developing thinner divers known as “skin divers,” due to the fact that they were designed to be worn without a wetsuit.
A particular variant of the skin divers became very popular: the super-compressor. Not only did they look cool—having two crowns and an inner rotating bezel was new—but they were also equipped with a unique technology that made them water resistant whilst being thinner. In this article, we will therefore discuss the technology of the super compressor divers and what made it unique.
Basics on Water Resistance
Before we get any further, let’s make something clear: no watch can be 100% waterproof. Watches are water resistant, built, and tested to certain depths. But water will always find a way to seep through a gasket and enter the case. To keep things simple, there are two core elements of a watch that makes it water resistant: the caseback and the crown. These two parts are the most vulnerable to water infiltration and brands have been working for decades to make them as tight as possible.
The traditional way of making a crown water resistant is to add gaskets on the threaded part and in the tube (in which the crown stem goes) to keep the water out. And, more often than not, crowns on dive watches do thread. However, some argue that this does not help with water resistance but only in keeping dirt and dust particles away. Others argue that it does help with the water resistance. (I personally believe it helps but that’s just my own belief.)
The caseback of divers is generally screwed down and the water is kept at bay by way of lodging a gasket between the caseback and the interior part of the case. Traditionally, the caseback is screwed down tight to create the seal, and the deeper a watch is supposed to go, the better the seal is. (Of course, other elements of the watch design come into play to make watches water resistant, for example the crystal.)
The EPSA Super Compressor Case
From the mid 1950s to the 1970s, dive watches were built as described above. The problem was that gaskets were not as reliable as they are today. Not being submerged in water on a regular basis meant the gasket would eventually dry up, or the continuous pressure applied on the gasket for being screwed in so tight meant wear and tear on the short run. In other words, one could not 100% trust that his diver was water resistant the way it was supposed to be when needed. So the case manufacturer Ervin Piquerez SA (EPSA for short) set out to remedy this problem.
Their genius concept of the super-compressor came from the need to keep dive watches water resistant without putting too much wear on the gaskets. They created a system of spring-loaded screws on the caseback that push toward the case the deeper someone goes under water, therefore, the more pressure is applied on the watch. This means that outside of the water, little pressure would be put on the caseback and the gasket, which is fine since it’s not needed. But diving to 40 meters and then deeper would apply more pressure on the caseback, gradually increasing its sealing capability.
The End of the EPSA Cases & Modern Iterations
For all of its ingenuity, the EPSA cases eventually stopped being produced. The cost of making these cases was too high while technologies evolved in a way that the super-compressor cases were no longer needed. Making divers water resistant became easier and cheaper, and the good old way of screwing down cases was alright. As mentioned in the introduction, however, super-compressor style watches did not go out of fashion. That is because they looked different and represented an era of daring underwater exploration and because, to put it simply, they looked cool.
So, for many years brands continued to create super-compressor style divers. This meant making divers with an inner rotating bezel and two crowns but without the EPSA-style sealing technology. That was until recently when independent brands brought back this technology and improved upon it, making it cheaper to produce. A good example of a brand that does this well is Christopher Ward and its C65 Super Compressor model.
Although the EPSA cases are no longer being officially produced, the company left a massive impact on the watch industry. The Super-Compressor case—which came in many variants, by the way—was unique and showcased the ingenuity of watchmakers to make watches more reliable and more wearable. Although ESPA no longer exists, one can find many homages to the original Super-Compressor technology. The best living example of the EPSA case can be found in the Sherpa OPS and Ultradive models, for which the EPSA technology was brought back to life by a Swiss engineer.
Featured image: www.vintage-breitling.com