The best way to avoid spilling coffee in a cup while walking may be to challenge the cup industry to re-design its takeaway products, suggests a new study on human movement by two ‘fluid scientists’ in California.
According to a report in the professional journal Neuroscience, researchers at the University of California at Santa Barbara calculated the frequencies at which coffee sloshes back and forth when held in cups of differing sizes, from shot cup to cappuccino mug. They found that each step amplifies the back-and-forth motion of the coffee, with the result that at any point between the seventh and tenth human step, the risk of spillage is greatest.
There is apparently a solution. It appears that coffee drinkers are observed to walk quickly with their cups, perhaps the result of the subconscious desire to reach seat, desk or table before the coffee spills. It is, say the scientists, exactly this which causes the problem – the faster the human walks, the closer their gait comes to the natural sloshing frequency of coffee. To avoid causing the oscillations that lead to a spillage, drinkers should walk slowly.
The second suggestion is that when humans watch their cups, the average number of steps taken before spilling coffee increases greatly. It was said that the researchers could not decide whether this ‘focussed carrying’ decreases the risk of spillage because we go through ‘targeted suppression’, which is automatically counteracting the sloshing of the liquid with small flicks of the wrists, or because the drinker simply takes more care when looking at the way the coffee is moving in the cup.
Fortunately, this research does not appear to be as pointless as it sounds.
The serious aim of it was not coffee at all – the beverage was simply a convenient liquid for an experiment in measuring object manipulation, in the way that various physiological systems, including the central and peripheral nervous systems and the musculoskeletal system, work together to create ‘movement strategies’ to overcome the problems presented by a ‘dynamic object’, such as a cup in which the contents move apparently unpredictably in transit.
The results may have important implications in working on the needs of the elderly, and sufferers from motor disorders such as cerebral palsy.
However, with regard to the matter of coffee sloshing, one of the researchers did appear to have some suggestions to put to the beverage trade. It was pointed out that ideas from the results of previous ‘liquid sloshing engineering studies’, for which the purpose was stabilising fuel tanks inside rockets, might be helpful in the matter of takeaway coffee carried by pedestrians.
The researchers offered various possibilities for spill-free takeaway coffee cup designs: the most practical was a series of annular ring baffles arranged around the inner wall of the container to achieve sloshing suppression by restricting liquid oscillation.
In an attempt to move the science forward this was put to several of the UK’s major takeaway cup manufacturers, with a request for their expert comments. As yet none of them have replied.