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.
“I mostly work on volcanic eruptions,” says Fabian Wadsworth, an earth scientist at Ludwig-Maximilians-Universität München in Germany. He first became interested in the physics of making espresso as a pedagogical tool to teach students fundamental concepts of percolation. “Coffee felt like a natural way that students