Horological repair, restoration and machining

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Testing - Water resistance tests are made in laboratory conditions and indicate the watch’s state of water resistance during the test only.  Once the watch leaves these conditions and is in the real world its water resistance can change due to use. 

There are both dry and wet methods of water resistance testing.

Dry testing is preferred because the watch stays dry, the test is quick and has definitive printable results. Also, test parameters can be controlled precisely and repeatedly.  The watch is placed in a chamber and a probe measures the deformation of the crystal under a prescribed pressure and or vacuum over a period of time usually seconds to minutes.
Water resistance - Testing dry