eli5 Why do some cups, glasses and bowels pour easily while others have the liquid run back down the container?

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Some cups, etc are easy to pour from, even without lip designed for pouring. While other cups make a mess. Is it just the thickness of the the lip? I feel like coffee cups are particularly bad.

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Anonymous 0 Comments

Water (and liquids made from it) like to stick to things, but that stickyness has its limit. Some vessels, by having a kinda “pointy” pouring lip, take advantage of this, because the water follows the curve but the lip stops abruptly, “freeing” the water because it cannot go around and up the lip as it would need more stickyness than it has.

With other containers, you can limit how much water it sticks to the outside by not pouring it slowly, taking advantage of another trait of water: it likes to stick to itself. As long as you’re decisive and you’re not trying to “pour a drop”, you should be fine.

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