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General information about water resistance (DIN 8310)
• Watch cases that are resistant to perspiration, drops of water, rain and so
on are called “water-resistant”.They must be able to withstand immersion
in water for 30 minutes. These watches are intended for normal, daily use
and may not be used in conditions where water pressure and temperatures
vary significantly.
• The test conditions are more stringent when a pressure has been specified
(e.g. “3 bar”). The indication of a pressure of “3 bar” may not be confused
with diving depth, it is only the definition of the test pressure. The test
pressure of “3 bar” is reached at a depth of 30 metres.
• The sealing elements may be exposed to pressures that exceed the
guaranteed test pressures during swimming and jumping into water.
Watches are particularly at risk when the wearer jumps into water after
an extended period of sunbathing because the impact pressure is then
added to the negative pressure that cooling causes, which may then
easily cause damage.
• It is important to check the performance characteristics of DIN-compliant
watches and to replace the seals, if necessary, when the Batterys are
changed.
Water resistance is not a permanent property. It should not only be checked
annually but also before the watch is exposed to particular stresses due to
the fact that the fitted sealing elements deteriorate in everyday use and thus
lose their function over time.
• Watch cases are precisely assembled from several materials whose
coefficients of expansion may vary in fluctuating temperatures.
• Special designs with fitted seals exist so that water resistance for specific
requirements may still be ensured. These are subject to a process of
natural ageing. They are attacked by, among other things, perspiration
and acids.
• DIN 8310 sets out the criteria for the design and test pressures that new
watches must be capable of withstanding. The resistance is stated in bars
and recorded on the bottom of the case.
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