Researchers Reveal Simple Trick To Make Your Coffee Stronger

The best way to brew strong pour-over coffee while using minimal coffee grounds.

Each year, tens of billions of kilograms of coffee are consumed worldwide. Yet, because coffee plants require specific growing conditions, cultivation can be challenging, especially as climate change continues to disrupt traditional farming regions.

To help meet the rising global demand for coffee, researchers from the University of Pennsylvania investigated how to optimize the use of coffee grounds in pour-over brewing. Their findings were published in Physics of Fluids by AIP Publishing.

“What we recommend is making the pour height as high as possible, while still maintaining a laminar flow, where the jet doesn’t break up when it impacts the coffee grinds,” said author Ernest Park.

In particular, the group found the thick water jets typical of standard gooseneck kettles are ideal for achieving this necessary height and laminar flow. Strong — but focused — water jets create an avalanche in the coffee grounds. Displaced grounds recirculate as the water digs deeper into the coffee bed, allowing for better mixing between the water and the grounds, and thus, results in a stronger coffee with fewer beans. If the water jet is too thin, it cannot adequately create this interaction to achieve a desirable strength and sensory experience.

Visualizing the Coffee Brewing Process

“If you have a thin jet, then it tends to break up into droplets,” said author Margot Young. “That’s what you want to avoid in these pour-overs, because that means the jet cannot mix the coffee grounds effectively.”

The dark color of coffee beans — and of coffee itself — makes it hard to demystify. Along with creating pour-over drinks with actual coffee grounds, the scientists supplemented their study with laser-illuminated transparent particles in a glass funnel to help thoroughly visualize the mixing dynamics and understand how the liquid jet affects the grains.

Though the group does not plan further studies related to coffee, they say there are many other parameters left to explore, such as the impacts of the size of the coffee grounds on the interplay between the physics and chemistry of the brewing process. When it comes to easy, accessible kitchen science, the researchers have some unorthodox advice: Do try this at home.

“We can really learn something from both the chemistry and physics point of view by looking at the kitchen,” said author Arnold Mathijssen. “It leads to new science where you didn’t expect it.”

Reference: “Pour-over coffee: Mixing by a water jet impinging on a granular bed with avalanche dynamics” by Ernest Park, Margot Young and Arnold J. T. M. Mathijssen, 8 April 2025, Physics of Fluids.
DOI: 10.1063/5.0257924

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