How to make a stronger coffee using less coffee grounds, according to physicists

Researchers in the US reveal how the way you pour hot water, and with what sort of kettle, affects flavour when making pour-over coffee

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Published: 6:15am, 15 Apr 2025Updated: 7:53pm, 23 Apr 2025

Physicists have discovered a way to make a stronger coffee using less coffee grounds when brewing it by hand.

Filter coffee – made with ground coffee beans that are soaked in hot water filtered through paper into a container – remains one of the most popular ways to enjoy coffee, whether it is prepared with a machine or made manually.

This latter method is known as a manual pour-over, and it involves slowly pouring the hot water in a circular motion over the coffee grounds by hand. The method, invented in the early 1900s, has seen a resurgence in popularity in recent years.

Researchers writing in the journal Physics of Fluids explain that the key to maximising flavour lies in the height and flow of the water stream.

Filter coffee remains one of the most popular ways to enjoy coffee. Photo: Shutterstock

Using a swan-neck kettle, which allows for precise pouring, creates a strong, concentrated jet of water that stirs the coffee grounds.

This motion, described as an “avalanche effect”, circulates the grounds and allows the water to penetrate deeper into the coffee bed, resulting in a stronger, more flavourful brew.