The Science Of Coffee Spills: It's All In The Walk

Are you nursing a burn from coffee you spilled on yourself this morning as you rushed from the café to work? Do you have a burning to desire to know why coffee spills seem so unavoidable?

Turns out you may have more control over your coffee than you think.

A new paper from two University of California Santa Barbara engineers finds that walking can easily cause coffee to slosh back and forth, like a pendulum, due to the liquid's low viscosity. Meanwhile, slight irregularities in a person's steps or movements can push those oscillations over the top and onto their hand.

Hans Mayer and Rouslan Krechetnikov detailed their findings in a paper published in the journal Physical Review E in April.

In their study, the pair asked people to walk back and forth with mugs of coffee while either looking straight ahead or down at the cup. Mayer and Krechetnikov recorded the subjects' movements and used a sensor in the mug to detect exactly when coffee spilled.

Those subjects that kept their eyes on their coffee were less likely to slosh it out of the cup -- Mayer and Krechetnikov aren't exactly sure why this is, but may have something to do with the mug carrier compensating for any oscillations they see in the liquid, according to an American Physical Society writeup by Jessica Thomas.

While the easiest way to keep coffee from spilling is to not fill the cup all the way to the top, there are a number of solutions that let caffeine hounds hustle with cups filled to the brim without getting scalded.

One option is a plastic plug designed to stop spillage by sealing off the siphole in a coffee cup's lid. Other companies have developed lids for to-go cups that have rotating latches that close off the drinking spout, or plastic lids designed to act like a toddler's sippy cup.

One device allows you to fight physics with physics - the Spill Not, which is a simple carrier made of a saucer-shaped base attached to a nylon loop handle. As someone walks along holding a cup of coffee on the Spill Not, the horizontal force resulting from that walking is not transferred to the saucer or the cup.