Why does water make plastic cards stick together?


I’m taking extra care with cleaning precautions during the pandemic. Every so often, I’ll take the plastic cards (e.g. driver’s license, credit cards, etc.) and throw them into the bathroom sink to wash with soap and water.

Before they dry, I’ve noticed that they tend to stick together while they’re wet. The water appears to make the plastic cards stick together, and you basically have to either slide them apart or pull them apart. Why does water do this with plastic cards, but it doesn’t seem to work with any other objects?

In: Earth Science

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Surface tension. Water likes to stick to itself, and other things. Normally on cards there’s little rough pits and dips in the card that lets air between so makes it easy to pull apart. When water is in there it wants to stick together and won’t let air in easily to separate the cards.