PeterCDE
10167
I´d guess that´s normal
Hi Mike,
it is recommendable to have dive watches for underwater use inspected every year, to ensure sealings/gaskets are intact.
Thus i´d not worry, because leakage is different from thermal influence!
On the phenomenon, it´s in fact a bit strange.
To me it seems it is NOT the absolute temperature; even 2 hours may not be sufficient to cool down all elements inside the piece from room temperature to sub-zero degrees.
What i´d guess is the rapid change in temperature, which does cause metal to contract. This can have some force, keeping in mind sudden temperature changes even can go so far to alter the structure of a metal (which is called hardening or tempering, although it requires heating up the workpiece to red heat).
Specifically, my guess would be the hairspring to change in length due to the contraction of the coils; actually this is a normal process and the different timing results indicate the piece just didn´t have sufficient time to adjust for the new environment temperature.
If you wish to go that far, i´d check the rate under sub-zero temperature for a longer time which allows the metals inside to completely cool down. Since it´s not stopping, the lubricants apparently do work well and subsequently, the rate change may be smaller.
Based on the timing result under room temperature, it seems to work fine.
Over all, i agree in that it´s quite a surprising phenomenon, but not suggesting need for service.
I´d recommend to have it checked annually; there´s a tool for water-resistance tests which all serious dealers should have and the testing requires a few minutes only, without need to open the watch. The seals and gaskets are apt to react to surfactants (tensides, detergents, such as soap or cleaning solution), which may be good to check before underwater use of the watch.
Cheers,
Peter
Seahawk II Pro