Why does cling film cling?

Question from Brendan Walker

Cling film’s stretchiness, combined with a dose of static electricity, allows it to stick to surfaces. Cling film is a thin sheet of either PVC or low-density polyethylene. This plastic’s long, coiled-up molecules give it some stretch, allowing it to be pulled taut over plates or bowls.

Separating the top layer of film from the roll tears electrons away from the atoms of either surface. Since electrons carry a negative charge, areas that have lost electrons end up with a positive charge, and patches that have gained electrons acquire a negative charge. The patches of electrical charge then stick to anything with an opposing charge.

Answered by Alex Franklin-Cheling for Brain Dump in How It Works issue 112

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