Penn study finds higher pour boosts coffee extraction efficiency
Penn researchers found a tall, steady pour can extract more from the same dose, so a better cup may start with fewer grounds.
A thick, continuous pour from about a foot above the bed can pull more flavor out of the same dose of coffee. A higher, laminar pour creates an avalanche effect in the grounds, opening the door to a stronger cup with fewer beans.
The study, published April 8, 2025 in Physics of Fluids, was titled Pour-over coffee: Mixing by a water jet impinging on a granular bed with avalanche dynamics. The work centered on a simple pour-over question with a practical answer: how to get more extraction efficiency without changing the brewer or chasing a finer grind.
To watch the brewing dynamics, the team used actual coffee grounds and transparent silica gel particles in a glass cone. A laser sheet and high-speed camera showed how the water jet struck the bed, triggered motion through the particles and kept mixing the slurry. The goal was to improve extraction efficiency so fewer grounds could produce the same strength and sensory experience.
The key was not just height, but control. The best pour is as high as possible while still maintaining laminar flow, and a standard gooseneck kettle helps because it keeps the stream smooth. A thick water jet from that kind of kettle is ideal for holding together at higher pour heights. If the stream gets too thin or breaks into droplets, the mixing weakens and the avalanche effect falls apart.
The same flow-and-erosion mechanics could help explain waterfalls and surface erosion. The researchers do not plan more coffee studies right now, but they still see room to test other variables, including coffee-ground size.
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