[DaveInLA]

I foolishly left one of my watches sitting in the way of direct sunlight for about 40 minutes. It's ~85 degrees outside today. When I recovered the watch (titainium case), it was a hot to touch as you would expect, but not burning so that it couldn't be handled. The whole case, bracelet, crystal were definitely pretty heated up. I took it away from the sun and kept it on my wrist in room temp.

This just happened and the time seems to be accurate. Anybody know if this type of exposure can cause harm to the movement? Was this type of heat enough to cause any expansion or distortion of the metals inside? I intentionally didn't cool it down rapidly (ex, fridge) because I didn't want a sudden change in temperature extremes.

 

[Dr. Robert]

the manuals say don't leave cameras, ipods, etc. in sun/heat............good idea for watches! One thing....I worked outdoors for a while, spent a lot of time at the beach in the sun...after a while my watch's black dials faded....

 

[polishammer]

I don't think it is a good idea to do it on regural basis, but once in a while it would not hurt anything. I have left one of my watchs in deirect sunlight for couple of hours and it got to about 150F on the surface measured with laser thermometer. That's been a while ago and the watch still runs great. I also had a watch delivered that came in a padded envelope and the delivery guy left it in front of my garage in direct Georgia sun. The watch was sitting there for about 7 hours, was so hot that I could not hold it in my hand. It was quartz though, but still, electronics do not like the heat, more so than mechanical. Year later the watch still runs like a champ.
Long story short, if it happens once, you should be ok, if you make this an everyday occurrence, then you will have a problems in the long run.

 

[Dangerjon]

You should be just fine. Probably the most destructive force that your watch could face would be heat and moisture. Heat and humidity can lead to greater wear on the gaskets of a mechanical watch, which can lead to moisture damage. However, heat alone probably will not foul your watch. As already mentioned, direct sunlight can certainly foul up the painted parts of your watch, such as the dial, hands, bezel, or what have you.

 

[Isthmus]

the sunlight is an issue for colored surfaces (prolonged exposure can cause them to fade). The heat might be an issue to plastic parts - depending on the watch heat can warp plastic parts (I've seen this happen). On a mechanical watch the extra head might also cause lubricants to become more fluid and run, but since there are minimal quantities of those in the watch, I doubt this would be a real issue.

 

[John MS]

I foolishly left one of my watches sitting in the way of direct sunlight for about 40 minutes. It's ~85 degrees outside today. When I recovered the watch (titainium case), it was a hot to touch as you would expect, but not burning so that it couldn't be handled. The whole case, bracelet, crystal were definitely pretty heated up. I took it away from the sun and kept it on my wrist in room temp.

This just happened and the time seems to be accurate. Anybody know if this type of exposure can cause harm to the movement? Was this type of heat enough to cause any expansion or distortion of the metals inside? I intentionally didn't cool it down rapidly (ex, fridge) because I didn't want a sudden change in temperature extremes.

The movement will probably survive just fine, although repeated trips into the sun may thin the oil enough that it flows away from some surfaces. I suspect your movement is just fine.

I would be more concerned about the dial, bezel and any other parts made of more than one type of material. Different expansion and contraction rates could result in cracking. Additionally, plastic parts have been known to simply melt and deform. That happened to someone on SCWF with a solar cell watch.

Remember the crystal covered watch traps heat. If you don't see any cosmetic damage I suspect your watch is fine.

 

[Isthmus]

Indeed. Check out what happened to Crew's watch when he left it under a lamp and it overheated:

https://www.watchuseek.com/showthread.php?t=221227&highlight=chapter+ring