News Physics

The secret to perfect espresso? It’s physics

The key is tight control of the interaction between water and coffee grounds

Espresso pours from a machine into a cup.

A new equation calculates the permeability of ground coffee to water, to help pull the perfect shot of espresso.

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By Taylor Mitchell Brown

A memorable shot of espresso is less about roast and more about percolation — and now there is an equation to back that up.

The physics explaining how gases bubble through volcanoes or how water and oils flow through Earth’s crust can also help quantify the perfect percolation of hot water through ground coffee, researchers report in the April 1 Royal Society Open Science.