Waterproofing a watch is easy. Keeping it waterproof is the challenge. Most modern watches are designed to be waterproof. Just by fitting the parts together with the proper gaskets in between they will be water proof (provided there isn't a defective part). So a new or recently overhauled watch will most likely be waterproof. Just to make sure, they are tested. First, let’s talk about the definitions. 1 Bar = 1 Atmosphere (ATM) = 33 feet = 10 meters These terms have specific scientific definitions and are not exactly equal. For the purposes of the watch industry, they are close enough. A watch that is tested to 10 bars will be good down to 330 feet or 100 meters. Dry Testing Most watches can be tested down to 10 or 20 bars with a dry testing procedure. One of the machines is pictured below. The watch is put into a chamber and the air pressure is pumped to the desired level. In the chamber is a digital micrometer which can measure to a millionth of a meter. It is situated just above the watch's crystal. As the pressure is increased, the watch case is actually compressed slightly. After the desired pressure is reached, the micrometer is monitored for a minute to see if the case starts to expand. If the case expands, it means that air is entering the case and it is not waterproof. Some watch companies also specify a vacuum test that is done the same way. Testing with air avoids the possibility of the movement getting wet. If the watch fails the test, you would not know where it leaked so a different piece of equipment is used: The watch is hung in the chamber above the water and the pressure is pumped up. The pressurized air enters the watch through the leak. This can take a while if the leak is small. I usually leave it for half an hour. The watch is then lowered into the water and the pressure in the chamber is allowed to escape. The pressurized air will then escape from the watch through the leak. You can tell where the leak is by looking for the bubbles. This test can usually be done without the watch getting wet inside. Occasionally, the crystal will blow off. The movement gets wet and the dial can even be damaged. It makes for a happy watchmaker. Wet Testing With dry testing, watch cases can only be tested to a depth of 10 or 20 bars depending on the equipment used. Many companies require wet testing on the cases designed for deeper depths. Once again, specialized equipment is used but in a surprisingly “low tech” way. The equipment is filled with water and the watch placed inside. The water pressure is cranked up (by hand) to the specified level - up to 125 bars on the equipment pictured above. The watch is allowed to sit in this pressurized atmosphere for half an hour or more. After the specified time, the pressure is released and the watch is removed. Next, the watch is placed on a heating element and warmed to about 120˚ F. (Now for the “high tech” part) A drop of cool water is placed on the center of the crystal. After a couple of minutes, the inside of the crystal is examined with a loupe. If there is condensation, it failed the test. If not, it passed! A watch can leak at any place where something is attached to the main body of the case. This would include the crystal, back, crown, helium escape valve, pushers, etc. The pushers on a chronograph can be especially troublesome devices. They can pass a static test, but when used under water, actually fail and inject water into the case. Many manufacturers don’t mention this in their handbooks, but when asked they usually discourage use of the pushers under water. For the do-it-yourselfers, the dry testing equipment is available for only $5000 to $6000. The high pressure equipment can be had in the same range. Just a couple of more thoughts about waterproofing and what it means to your watch. All of these are static tests where the pressure is slowly raised and lowered. How much water pressure is exerted on a watch as it is forced through the water while engaged in sports like skiing or diving? The answer depends on many factors. Below is a copy from the Oris product manual - also available on their site. Notice that they don't even want you to shower or swim with your watch unless it is tested to 100M. This is typical of the advice from most companies. Your watch does not have to exceed its specified depth to get wet. Also remember that waterproof testing is just a snapshot of your watch’s present condition. It is no guarantee of future performance. A quick check by your watchmaker every spring will not guarantee that your watch will be waterproof all summer. The gasket materials used on a watch do eventually break down and fail. Their demise can be accelerated by heat, chemicals and even UV rays- depending on which products are used. The only way to avoid this problem is to replace these parts on a regular basis. Most manufacturers recommend every 4-5 years. Thanks to Steve / N2FHL for this installment!
There are more coming. This one, and the next on Positional Error, were written by watchmaker and member N2FHL / Steve.
I know you are reposting these older articles that you have already posted elsewhere, so some of the information in this one is certainly not relevant currently, and when I get some time I'll clarify and expand on a few things... But the key one is what the water resistance rating of the watch means in "real life" and for any reputable company, 30 m depth means you can actually take it to 30 m. I can't speak for Oris, but for Omega there's no doubt that the depth they say on the dial is the depth that the watch is good for... Cheers, Al
Just to expand on a couple of things above since water resistance testing is a hot topic here at the moment... The dry testing described above is a very simplified version of what is actually going on during the testing. First the test are typically done in two stages, and most start with a vacuum test, and then after that move on to a pressure test. The vacuum test removes air from the testing chamber, and in that scenario the case expands. In the pressure testing phase, the case would be compressed. The various programs on the machine take into account the construction of the watch, the diameter, and what it rated to. So a dress watch with an acrylic crystal that is under 40 mm would be tested very differently to a sapphire crystal watch that is 42 mm for example. These machines do more than just check for a change in deflection, so the fact that a watch under pressure may expand would not cause a failure as stated above. These machine are looking for a specific pattern of movement in the watch case, rather then just movement in itself. So there would be initial compression, settling, some rebound, and then a period where things should be mostly stable. Measurements are taken at the level of 100th of a micron on the machine I use. The dry testing machines shown are older versions, so not sure what their capabilities are, but for more up to date equipment if the case is found to be leaking, the machines have a "leak detector" program to help identify where the leak is coming from. This is an extended pressure test really, over a much longer period of time than the normal test is. The machine again monitors the deflection, and at the end of the test it will tell you if the watch is safe to submerge in water or not. The idea is the same as the hand pumped machine shown above (looking for bubbles escaping from the leak, but in a glass of water), but without the risks involved in using that machine, such as a blown out crystal - that's why brands like Omega and Rolex do not allow these hand pumped machines as part of their pressure testing regimes. To see more on pressure testing, please have a look here: https://omegaforums.net/threads/pressure-testing-a-watchco-sm300.45375/ Cheers, Al