Water Resistance - Watch Education

Beyond fashion and convenience, the transition from the pocket to the wrist brought a host of potential function and failures to the mobile timepiece known as the watch. In this transition the often-exposed movements and inner workings of the pocket watch needed a higher level of protection from both impacts as well as the elements.

Beyond fashion and convenience, the transition from the pocket to the wrist brought a host of potential function and failures to the mobile timepiece known as the watch. What was once safely ensconced in a vest pocket was now out in plain sight for all to see. In this transition the often-exposed movements and inner workings of the pocket watch needed a higher level of protection from both impacts as well as the elements.

In advance of the positional transition of the watch from pocket to wrist, keyless winding (patented by Jean Adrien Philippe of Patek Philippe fame) did much to mitigate the effect of a wide-open aperture needed to insert a key to wind the watch every day. Even still, full hunter cases allowed the back to be easily opened to view the movement, and as beautifully decorated as some of these mechanisms were, showing them off or simply enjoying the view of your own ticking timepiece was a common event. While this may not have let liquid water in (who would open a pocket watch in the rain?) it did allow dust, debris, and water vapor to enter the inner sanctum of the era’s timepieces calling for more regular cleaning and servicing than we expect of today’s mechanical wristwatch.
 
Once placed on the wrist, the likelihood of exposure to the elements was compounded. In addition to the odd squall, the convenience and location of the watch upon the wrist expanded its potential for use in sport, war, and a wide scope of activities that demanded a higher level of shock and water resistance.  

Focusing on water resistance we all recognize the real-world value of a watch that could accompany the nascent SCUBA divers under water in an era before dive computers. Beyond that small group of aquanauts pushing the limits of both human and machine, water resistance also has a meaningful value protecting the inner workings of almost any watch from rusting. Whether from an occasional splash from doing the dishes, getting caught in the rain, or taking a quick dip in the pool, liquid water must be held at bay. Beyond that, water vapor must also be kept out as much as possible as it can also have deleterious effects on a mechanical & quartz watch movements.
 
So how are watches made water resistant?
When you think about it you have three ingress points for both liquid and vapor in most watches (nothwithstanding chronographs, repeaters, and other multi-function watches with extra apertures in the case). These include the stem/crown combination, the case back, and where the crystal meets the case. In each of these locations a seal of man-made materials may take the shape of an “I” ring, “O” ring, or even and “L” shaped ring. Getting the size right in each of these systems allows them to compress between the structural components and keep out the elements and dust. Getting the size wrong on these seals can lead to serious problems. In most cases the seals – especially on the back also need to be lubricated to perform to the maximum potential – something not often done by the man at the mall changing the battery on your quartz watch.  Most watch enthusiasts are also quite aware of what is the bane of the watchmaker’s existence; the infamous screw-down crown. While these can an do offer an upgrade to water resistance, they are simultaneously the prime source for water entry into watches. Not because the systems fail, but rather via user error. As an example: you take off your mechanical watch to wind it (or to change the date or time on any type), unscrew the crown, perform the function, push the crown back in and voila – your watch is running. This is where the problem lies. Too many owners simply forget to screw the crown back down and go on about their business as if the watch rated to 10, 20 or more atm is good to go. It is not. While most watches have a modicum of resistance even when left unscrewed, don’t be surprised when the crystal fogs up after that refreshing swim. Having surveyed numerous watchmakers this is far and away the greatest cause of service and repair issues in most shops. 

What kind of water resistance do you really need?
If you think about it, a 3atm watch is technically rated to submersion to 68 ft (1 atm already applying pressure before submersion and 2 more underwater. At 33.89 feet per submerged atmosphere you might think it’s ok to swim or snorkel. Don’t do it! While the numbers may add up, fluid pressures from swimming and rapid temperature changes are not typically handled well by a 3atm watch. These should be occasional splash and rain only. A 5atm watch is better – and may even withstand occasional submersion like doing the dishes or even a quick fall into the pool, but it’s best to go for a 10atm rating for extended or substantial submersion; swimming, snorkeling, etc. For actual SCUBA diving you need to look for a 20atm rating and for that tiny percentage of professional mixed gas divers, the standards are even more extreme to 30atm or more with extra precautions to prevent the crystal from exploding off the watch from helium over pressure when returning to normal pressures from saturation diving.   

Anything over 30atm is pure marketing hype. While some collectors may appreciate it for its own sake as well as claim it represents superior overall quality, it is a superfluous mark of over-zealous engineering in support of the sizzle over the steak. Kind of like making an automobile that could drive 500 MPH.