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The quest for perfect coffee -

Researchers at the University of Pennsylvania set out to find the best pour-over coffee technique, using fluid mechanics to extract the most flavor from the fewest beans.

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The secret weapon: a gooseneck kettle -

Using a gooseneck kettle and pouring from a height creates an "avalanche" effect in the coffee grounds, maximizing contact and improving extraction for a richer brew.

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Flavor from fewer beans -

This technique allows coffee drinkers to use fewer beans while still extracting robust flavor, especially helpful during times of rising coffee prices and tighter budgets.

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Coffee as a luxury -

Bad weather and rising tariffs in coffee-producing countries like Brazil and Colombia have driven up coffee prices, making daily coffee feel more like a luxury than a routine.

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A solution from science -

This newly published coffee-brewing method could help people make their grounds go further, thanks to curious physicists and fluid mechanics experts who just really love their coffee.

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An idea at the coffee table -

The idea started informally around the lab's coffee table, where researchers began wondering how to get the most flavor from minimal coffee during casual conversations and caffeine breaks.

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Publishing the coffee break -

The findings were officially published in a journal called Physics of Fluids, under the title: 'Pour-over coffee: Mixing by a water jet impinging on a granular bed with avalanche dynamics.'

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Latte art meets lab work -

While others were admiring latte art, these scientists turned their focus to the underlying mechanics of coffee preparation, looking beyond aesthetics to improve taste and efficiency.

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Coffee meets fluid mechanics -

Professor Arnold Mathijssen explained to USA Today that the coffee experiments began casually at the lab's shared coffee station, a bench corner where science and caffeine collided daily.

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Trial, error, and caffeine -

What started as casual tinkering with pour techniques soon evolved into structured experiments, meticulously recorded in a lab notebook by a team of highly caffeinated scientists.

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Taking it to the next bench -

The team moved to a better-equipped lab bench to control variables like pour height and water stream. The aim was simple: find out what was happening inside the filter.

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A visibility challenge -

Coffee grounds are opaque, making observation difficult. To understand what was happening, they needed to simulate coffee grounds with see-through materials, and some clever optical tools.

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Science behind the scenes -

The team built a clear pour-over filter filled with silica gel, illuminated it with a laser sheet, and captured the pour with a high-speed camera to study fluid behavior.

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Custom code for coffee -

Using custom Python and Matlab code, they analyzed how the water jet interacted with the simulated coffee bed. The goal: understand how movement affected extraction efficiency.

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Avalanche in a cup -

Their findings revealed that pouring from a higher height caused a granular "avalanche," stirring the grounds and exposing more of them to water, key for flavor extraction.

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Maximizing contact time -

Longer contact between water and coffee grounds improves flavor. But the pour must be just right. Too slow, and water may not mix evenly with all the grounds.

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Avoiding uneven extraction -

A very slow pour can result in under-extracted or over-extracted coffee. Balanced water flow is essential for a cup that tastes rich, not bitter or weak.

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Height adds velocity -

Pouring from a greater height increases the velocity of water, triggering the ground avalanche. This movement ensures maximum surface area contact and a more even extraction.

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Avoid the drip-drop trap -

Pouring too high or too slowly can cause the stream to break into droplets. A broken stream stops the avalanche, leading to uneven flavor extraction.

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Stream, not sprinkles -

To achieve a continuous pour, aim for a laminar stream, which is a smooth, unbroken flow. It's the secret to activating the avalanche and optimizing extraction during pour-over.

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Why a gooseneck kettle? -

A gooseneck kettle helps control the pour rate and stream thickness. It's the easiest way to produce a steady, laminar stream for a perfect pour-over experience.

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Flavor in the flow -

Experiments showed that a slow, controlled pour resulted in the most flavorful coffee. The stream's behavior affects the entire brewing process, and ultimately, the taste.

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Solids tell the story -

To measure extraction, scientists evaporated brewed coffee and weighed the remaining dissolved solids. This showed how the pour method directly affected how much coffee made it into the cup.

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Coffee adds to science -

Though the lab's usual work includes bacterial behavior in fluid flows, this experiment adds to scientific knowledge in a very delicious and relatable way: making better coffee.

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COVID and culinary curiosity -

During COVID-19, with their lab closed, the team pivoted to food science. Kitchen experiments kept their curiosity alive and even led them to publish research in culinary fluid mechanics.

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Outreach with coffee science -

The lab now uses coffee science to engage local students in physics. Their kitchen science outreach program makes complex ideas fun and accessible through relatable experiments.

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Espresso and French press studies -

Previous research focused on fluid behavior in espresso machines and French presses. But pour-over remained largely unexplored, until now, thanks to these coffee-loving physicists.

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Pour-over, perfected -

As far as the team knows, this is the first scientific analysis of pour-over technique using fluid dynamics. Your morning brew may never be the same again.

Sources: (USA Today) (New Scientist) 

See also: Coffees from around the world you will want to try

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