Science Explains Why Coffee is More Likely to Spill Than Latte

Coffee drinkers have experienced more than once the spilling of their coffee. Everyone can assess that it’s not a very pleasant thing.

A team of researchers from the Princeton University has decided to find out the scientific explanation behind it.
According to the scientists, the layer of foam, or the bubbles that form at the surface of a drink can stop the “sloshing” movement of a liquid, either cold or hot, in a container.

Alban Sauret, one of the researchers who took part in the study, explained that he got the idea for the study while he was out in a pub one night and noticed that his mug was not spilling very much.
He also noticed that while handling a pint of Guinness, which produces a plenty of foam, there was no sloshing motion.

Another researcher noticed that when she ordered her usual latte, the lid didn’t need a stopper.
These two incidents made the researchers look for a scientific explanation of why this happens.

The experiment involved a solution of glycerol, water and dishwashing detergent mixed in a glass container.
The researchers wanted to see what would happen if they inject air in order to create a layer of bubbles. Each layer was approximately 2mm in diameter.

François Boulogne, one of the scientists involved in the experiment, explained that they needed the dishwashing foam because of its stability. This allowed the researchers to conduct the experiment without worrying that the bubbles might disappear.

The researchers then jolted the container filled with the solution, rocking it back and forth or moving it side-to-side very rapidly.

They used high-speed cameras to capture the way the container moved and noticed that it took five layers of foam to lower the

“wave height of the liquid bath by a factor of 10.”

The researchers wrote that only the bubbles that are close to the walls of the container play an important role in the dissipation of the energy inside it.

The scientists believe that the recent discovery could have practical uses that will help with the handling of liquefied gas in tankers or the transportation of propellants in rocket engines.
They detailed their new findings in the journal Physics of Fluids.
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