Cling wrap, or Saran wrap, works because it acquires an electric charge as it is peeled from the roll.
It can then stick to an insulating body by the same mechanism that an uncharged piece of paper sticks to the charged glass of your computer or television screen.
The mechanism relies upon the cling wrap and the object to which it is sticking being at a substantially different electrical potential.
This works when the object is an insulator.
When the object is metal, the charge on the film is dissipated throughout the object, so negating the effect.
Old cling wrap taken off the roll doesn’t work either. After a while, the charge breaks away, and the clingyness is lost.
Saran wrap becomes charged with static electricity as it peels from the roll.
You can sense the charge by peeling some off and holding it near your face, you will feel the hairs on your cheek stand up.
Metal drains away static, whereas glass, or plastic retains static on its surface.
The more static, the greater the cling and stickiness.
