Why Is It So Much Easier to Spill Your Coffee Than Your Beer?

Did you ever wonder why it’s way easier to spill coffee than beer? It's not because you're more careful when carrying beer. It’s because beer foam damps sloshing, researchers show.


Photo by: Okea


Did you ever wonder why it’s way easier to spill your coffee — as all those stained shirtfronts will attest — than it is to spill your beer? No, it’s not because you take more care when carrying your beer or, as one YouTube commenter has suggested, because you drink your beer more quickly. At least, it’s not only for those reasons.

Turns out it’s because the beer foam — obviously absent from your coffee cup — has a damping effect when you stop short and slosh your pint of beer.

Researchers at Princeton University and New York University presented a study at a recent meeting of the American Physical Society's Division of Fluid Dynamics concluding that beer sloshes, or oscillates, much less than water or coffee due to “the influence of the foam on the sloshing dynamics.” Furthermore, they determined: “2 to 3 layers of bubbles are sufficient to significantly damp the oscillations. For more than 5 layers of bubbles, the original vertical motion of the foam becomes mainly horizontal.”

The researchers, who hope their findings may prove helpful when applied to industrial liquid transport, have released a video — complete with snappy music — further exploring why beer is easier to carry than coffee. It was posted on YouTube by NYU’s Particles, Interface & Fluids Lab.

Certainly the findings are provocative. One commenter wondered if the foam in a cappuccino might render coffee equally difficult to slosh. Good question. Another saw the hand of fate at play, marveling, “[It’s] as if beer was made for drunk people.” As if …

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