If a Sinn watch is labeled water-resistant, it fulfils the requirements of DIN 8310 in its original specifications. Sinn guarantees that its water-resistant watches can withstand pressures up to at least 10 bar. This corresponds to the pressure at a depth of 100 m. Some of our classic masterpiece models are exempt from this. The water-resistance of each individual watch we produce is checked. The maximum depth given on many watches always refers to the maximum static compressive stress which the watch case is guaranteed to withstand. When swimming, or in a jet of water (washing hands or showering), there are also directional flows with dynamic pressure peaks which impact upon the relevant parts of a watch to a greater extent than the diving depth alone.
In order to use a watch safely when swimming we therefore recommend a compression resistance of at least 100 m. Diving watches are recommended for intensive and frequent use in water. The compressive resistance of a diving watch is given in bar or in depth, measured in meters. When diving, the pressure increases by one bar every 10 m.
In everyday use it is important to note that seals can suffer from wear or ageing and that small direct particles can build up in them as the result of a wide range of factors which arise when wearing a wristwatch. These particles can themselves assume a part of the seal function if the seal elements are already suffering from extensive wear. Tensides from detergents or similar cleaning agents can then coat such particles, making it easy from them to be washed away.
For these reasons the airtightness of a wristwatch should be checked on a regular basis (once per year).
For smartwatches, statements about water resistance usually refer to the so-called IP protection classes. The distinctions between these protection classes are used in electrical engineering to describe cases for ‘electrical equipment’ in terms of the protection they offer against water and dust and to enable this protection to be verified. The associated standard is DIN EN 60529.
Because this approach treats a watch as a piece of electrical operating equipment, the requirements and testing methods are not specific to wristwatch cases but have to be applicable to any protective case. The disadvantage of this is illustrated by the following example.
The protection class most commonly found with electronic watches is IP 67 (which corresponds to DIN EN 60529). The first digit, 6, indicates how dust-proof the case is. The second digit, 7, is determined by a water resistance test which, at first glance, corresponds exactly to the ‘designated stress’ for wristwatches as per DIN 8310 (water resistance): the device is immersed in water at a depth of 1 m for 30 minutes. But while DIN 8310 includes several sub-tests to ensure that the case is equipped to withstand this stress, the IP protection class test is limited to the immersion of the device in water at a depth of 1 m for 30 minutes. The reason for this difference is that DIN 8310 wants to test the case’s ability to withstand repeated immersion for short periods of time in shallower water depths, whereas IP 67 describes a one-off test process with the same situation.
To this end, DIN 8310 includes more stringent sub-tests than what is specified in its ‘designated stress’ section. Thus, the watch is exposed for five minutes to water pressure of 3 bar, which equates to a water depth of around 30 metres. To comply with DIN 8310, the watch also has to be exposed to a level of compressive stress 30 times higher than that of protection class test IP 67.
With DIN 8310, the watch is also immersed for 60 minutes in a water depth of 10 cm. So after the watch’s stability at a water depth of 30 m has been guaranteed, it is tested at very low pressure at a depth of 10 cm. When the case is immersed in shallow water, the seals are no longer being pressed against the sealing surfaces on the case as they are at higher pressure. This means that the seals have to be able to withstand capillary splitting effects themselves, using their own inbuilt compression.
Furthermore, DIN 8310 checks for any water that might have penetrated the case using a condensed water test (whereby water that has penetrated the case is vaporised via exposure to heat, causing condensation to form on the cooled crystal). In this way, even very small quantities of water can be detected because they form a thin layer of condensation on the crystal. In DIN EN 60529, by contrast, this test criterion (the amount of water permitted to penetrate the case) is expressly left open and is subject to the jurisdiction of a Technical Committee responsible for the specific product. If there is no additional information available for these test criteria for a watch tested using protection class IP 67, then the labelling of that watch as IP 67 is not really very meaningful.
Overall, therefore, it is clear that the watch-specific DIN standard
has significantly more stringent requirements when it comes to the word
‘water-resistant’ than protection class IP 67.