Evian bottles have a great design - you can push down on them, and easily crush them, which means they fit in your garbage with less room.
If you crush them, they begin to creak and expand until you refasten the screw top. Then the bottles stop creaking and retain their crushed shape.
Does the screw top somehow cause tension throughout the crushed plastic bottle, forcing it to retain its new shape?
Or does it somehow create a vaccuum? (I can’t see this being right, but it was my first thought)
The screw top does not create a vacuum, it just stops any air from being sucked in by the expanding bottle.
As your bottle expands from it’s chushed state air is needed to fill up the space created inside. If you prevent the air from entering, as the bottle expands the preasure inside goes down. Now your expanding bottle has to fight a losing battle against atmospheric preasure. In theory if your bottle were in a vacuum it would regain its shape with or without the screw top.
Try it with the palm of your hand instead of the screw top.
You will feel the suction.
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Hmm. Thanks for the explanation. I will experiment tonight at home.