Bear Can Suction: Physics at work

posted Jul 21, 2015, 8:18 AM by Paul Wagner
On our recent trip to Mono Pass and Pioneer Basin, we had something happen that really took us by surprise.  No, it wasn't the hailstorm that clobbered us right at dusk--although we had hoped we would miss that particular adventure.  But it's related to that.
Time to dry out our things...amid the hail  ©

The next morning, when we got up and inspected the damage around our campsite from the hailstorm, we were surprised to see about a half an inch of water sloshing around inside our Bearvault.  Huh?  The bear can was sitting away from our tent, in a small clearing among some trees, and it was upright the entire time---from before the storm hit to the next morning.

So how did all that water get into the can?  All we can imagine is that the small lip on the bear can that sticks out beyond the lid was saturated during the rain and hailstorm, and that the can and its contents were relatively warm from the day's hike.  As the contents cooled, they must have created a bit of a vacuum, and if the lip were saturated with water, maybe the vacuum sucked the water standing on the lip up through the threads and into the can.  And that continued for some time, because the storm lasted a while, and the really cooled down everything--there was still an inch of hail on the ground when we woke up the next morning.

Anybody got a better explanation?