I was recently caught in the rain while traveling wearing my ‘65 Astronaut. When got into the hotel I found some condensation under the crystal. The watch had been serviced prior and I replaced the back gasket and battery hatch gasket, but not the crystal.
Is there a crystal gasket that I should replace when I replace the crystal soon? Are there any replacements out there?
Can these watches be made splash proof again, or am I going to have to keep this watch only for fair weather days?
Condensation is not necessarily an indication of a leak.
The watch was opened and worked on, and when it was closed, there was a small amount of air inside the case, most of it between the dial and crystal. This air contains whatever moisture related to the relative humidity of the environment was at the time the case was closed.
Your wrist warms the watch up nicely, and a cool rain striking the crystal will immediatley condense some of the ambient moisture inside the 'micro-climate' that is inside the watch.
Depending on the watch, we would sometimes warm them up on a special (expensive) heater when I worked at a depot, thus driving away any moisture, or at least lessening the effect I just described. As an example, today I cased up some watches and our RH here was 79%.
Kind of high, so I warmed them up a bit with a hair dryer on low. You have to be very careful if you want to try this, depending on the watch, they can be VERY sensitive to heat and hot spots, especially some quartzes. Watches with little or no seal are not candidates for this, as they leak air like sieves, to the point that they 'respirate.' A lot of very old watches do this, they are not even dustproof.
There is no gasket used with the Astronaut crystal, It just a snap over type that can be installed by hand...