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Waterproofness of watches explained

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[5min reading time]

Watches and Water; what you really wanted to know!

Water damage is a watchmaker’s nightmare, and over the years an incredible amount of time and brainpower have been invested in preventing it. Some watch collectors are truly passionate about the engineering behind their 500m dive watch. Most of us are just happy when we don’t have to worry about waterproofness at all. With an abundance of articles and opinions about the topic, this short article provides all the information you need to know.

First and foremost, the truth is that no watch is waterproof. There is always a limit to how much water pressure a watch can take. Also, it’s important not to take the imprint or engraving on your watch’s dial or case-back literally. For example, 30 M does not mean that you can dive with your watch up to 30 meters in depth. It simply means that your watch passed a lab test that slowly applies pressure to a case and slowly reduces it. Such a lab test does not replicate the immediate change in pressure when swimming, thrashing, or diving from a platform. Such conditions can overwhelm the resistance of a 30 M watch instantly upon forceful contact with water.

Which m/ft number makes sense for me?

Most watches are more likely to see a swimming pool, coastal waters or lakes to test the waterproofness, than the bottom of an abyss-like body of water. Ideally, you are looking at a watch with a waterproofness of 10 ATM or 10 bar. ATM stands for atmosphere. 10 atmospheres are equal to about 100 meters or roughly 330 feet. A bar is just another way of stating atmospheres. All currently available Formex models are waterproof up to at least 10 ATM, making them ideal for daily wear and water-related activities. If you limit yourself to showering and swimming in shallow waters, you can also use a watch with a pressure of 5 bar. If you seriously consider diving with your watch, 20 ATM is the threshold for real diver’s watches.

Waterproofness of watches

How to avoid water damage in my watch?

A functioning gasket is what keeps your watch waterproof. In other words, you should do anything possible to keep it intact. Any material ages over time, but cosmetics, shower/bathing products, sunscreen or other chemicals can corrode the seal much faster. Make sure to rinse your watch with fresh water after using it in saltwater or chlorine. Also, try to regularly clean your watch with fresh water, mild soap, and a soft brush to remove any dirt. If you dare to open your watch yourself, you can wet the sealing gasket with some silicone oil. But remember that most watch brands will void your warranty if you work on your watch yourself. Generally, we recommend that you service your watch every 5 years. During such a service, all seals are being replaced and waterproof-tested. Just to recap, here’s how to avoid water damage in your watch:

  • ALWAYS screw in or push in your crown when wearing your watch
  • ALWAYS rinse your watch with fresh water after swimming in salt or chlorine water
  • REGULARLY clean your watch with fresh water, mild soap and a soft brush to remove dirt
  • Service your watch every 5 years and have all gaskets replaced and tested

What if it's too late?

Water damage in a watch is the worst-case scenario service nightmare, and if not taken care of immediately, will result in a memorable repair bill, especially with higher-end and vintage watches. If a watch shows signs of fog under the glass, moisture has entered. Rust is the enemy of steel parts in the movement and can cause serious damage to the dial and hands too. Particularly the luminescent mass will absorb moisture and start to rise like freshly kneaded dough. Now, every hour counts, so have a professional watchmaker open and dry your watch. Household tips like putting the watch in a bag filled with rice might work but are not recommended. Although water easily gets into a watch, it is very difficult to get it out again. For Quartz watches, the situation is similar. In addition to rust and rising luminous material, water can cause short circuits in the electronic movement.

Does a screw-down crown increase waterproofness?

It is often discussed whether a screw-down crown, vs a push/pull crown, positively influences the water-resistance of a watch. In my experience, the major difference is that a screw-down crown prevents the crown from accidentally popping out, although the risk of this happening underwater is minimal. In terms of daily wear, a push/pull crown is easier to handle, as winding the movement and changing date/time can be done on the go, without loosening and tightening the screw. However, in my opinion, for any watch waterproofed above 20 ATM, particularly a Dive watch, a screw-down crown should be standard.

Using the Chronograph function underwater

If you ever wondered how long you can hold your breath underwater, you might consider using your Chronograph’s stopwatch function. Modern Chronograph watches (including the current Formex Chronograph models) feature a double O-ring seal that prevents water from entering the watch when the pushers are applied underwater. However, if in doubt, consult your watch’s handbook or research before taking that deep breath.

Let’s talk records

In 2012, film-maker and explorer James Cameron navigated a specially designed submersible to a depth of 10,908 meters (35,787 feet). Attached to the outside of the hull was an experimental Rolex Deepsea Challenge watch, nearly 30 millimeters high, whereas the crystal alone occupies 14.3 millimeters of height. Seven years later, Omega found as a spot in the Challenger Deep that is a few meters deeper and set a new record at 10’028 meters with 3 identical watches fastened to a submarine. The Omega Seamaster Ocean Ultra Deep withstood the enormous pressure unscathed. To put this feat into perspective: the pressure at 10’000 meters equals 1 ton per square centimeter, the weight of a small car resting on the surface of a fingernail (ouch). The expedition was planned and financed by Texan investor and adventurer Victor Vescovo, who also collects Omega watches.

Deeper diving records of a watch are not known - except, perhaps, the timepieces that have found their way into the depths of the sea dropped from aboard a ship. Therefore, in addition to the waterproofness, always check the secure functioning of your buckle and make sure your spring bars are properly attached to the lugs, especially when your strap has a quick-release function.

Thomas Gronenthal Formex Swiss Watches Editor