Scientists release instructions for how to make a perfect cup of coffee
Show Caption
Hide Caption
Coffee tips to make the best brew at home
From storing to grinding beans, here's how to get the freshest cup of coffee at home.
ProblemSolved, Reviewed
A group of fluid mechanics and physics researchers at the University of Pennsylvania have created what they believe is the best pour-over coffee technique.
The key is using a goose-neck kettle and a high pour to achieve an "avalanche" in the ground coffee.
The technique results in the maximum amount coffee flavor extracted from the minimum amount of coffee beans.
Coffee prices have spiked significantly over the past four years as bad weather reduced production. Add in rising tariffs on coffee-producing countries like Brazil and Columbia and that cup of joe is looking more and more like a morning luxury.
But there's a newly-published technique designed to make your coffee grounds go further – courtesy of a slightly over-excited group of physicists and fluid mechanics experts at the University of Pennsylvania.
About a year ago, staff in Arnold Mathijssen's lab started pondering how to extract the most coffee using the fewest beans as they hung out at their lab's coffee table. They've just published their findings.
Titled "Pour-over coffee: Mixing by a water jet impinging on a granular bed with avalanche dynamics," their 10-page paper in the journal Physics of Fluids was published Tuesday.
Fluid mechanics and maximizing coffee extraction
"It began around our coffee station, which is basically a space on one of our lab benches," said Mathijssen, a professor of physics at the university.
One of his Ph.D. students, Ernest Park, is "the main coffee enthusiast in the lab," Mathijssen said. The lab's coffee-making apparatus include an espresso machine, a French press and a pour-over setup. "But pour-over is the drink Ernest really loves," he said.
A bunch of fluid mechanics experts, a lab full of equipment and a whole lot of caffeine: What could go wrong?
In this instance, it was, "What could go right?"
Experimenting at the coffee station
Park initially began simply trying out different methods of pouring the boiling water in his pour-over coffee. As any self-respecting science lab does, the group had a log book at the coffee station to record data about what made the best coffee.
"Initially, he was just trying out different things, pouring coffee from different heights and such. Then he said, 'Wait. This tastes good but we need to do the actual experiments," Mathijssen said.
They moved the effort to another lab bench and began experimenting with pour height and water stream size, but realized they needed better data to determine exactly what was happening in the coffee filter.
"We couldn't really prove what the mechanism was," said Mathijssen.
Coffee grounds being opaque – and a fluid mechanics lab being a fluid mechanics lab – the effort quickly ramped up.
Soon they had assembled a quantity of small silica gel particles about the size of coffee grounds, a see-through pour-over filter, a laser sheet to illuminate the setup from the side and a high-speed camera to allow them to film and analyze the resulting images using some custom-made Python and Matlab computer code.
It's all about the coffee ground avalanche
After doing dozens of experiments and analyzing the results, Park, Mathijssen and lab member Margot Young came up with a definitive technique to extract the maximum amount of coffee from the fewest number of beans.
In science terms, they were studying "the hydrodynamics of pour-over coffees, especially how a liquid jet interacts with a granular bed of submerged coffee grounds."
In layman's terms, they have this advice:
Pour the boiling water over the ground coffee slowly, so that the water has more time to be in contact with the grounds. The longer the pour time, the greater the extraction.
But not too slowly because that can result in the water not mixing completely with the coffee grounds, resulting in some of the coffee being under-extracted and some over-extracted.
Increase the pour height to increase the velocity of the water. This helps create an "avalanche" in the coffee grounds that causes them to be maximally exposed to the boiling water.
Insure that the water pours as a stream rather than breaking up into droplets. If you pour too slowly or go too high, the stream breaks and the avalanche stops. You want to maintain a smooth, laminar flow of water hitting the coffee.
A thin jet of water – most easy produced from a gooseneck kettle – was the easiest way to get a slow, laminar pour. It's possible to get a thin jet from a regular kettle but harder to do.
A slow, laminar pour (meaning a single stream of water and not droplets) resulted in the most flavorful coffee, the scientists determined. But the final part of the experiment was to test the actual amount of coffee solids extracted by analyzing the dissolved compounds.
This was done by making cups of coffee using various pouring heights and stream sizes, evaporating the coffee in an oven and then weighing the dissolved solids.
Does this add to science's body of coffee knowledge?
Admittedly, most of Mathijssen's research is more esoteric than this. Recent papers include "Collective intercellular communication through ultra-fast hydrodynamic trigger waves' and "Enhancement of bacterial rheotaxis in non-Newtonian fluids."
The coffee research came about in part because during COVID-19, when their lab was shut down, the team began a food science initiative "because it meant we could do some experiments at home," he said.
This resulted in papers such as "Culinary fluid mechanics and other currents in food science," published in 2023. They've since began outreach to local schools to do kitchen science seminars to raise student interest in physics.
For the coffee experiments, a literature review showed there had already been research into the fluid mechanics of the liquids involved in espresso machines and also French press coffee makers.
"But as far as we know, there's nothing yet on pour-over coffee," Mathijssen said.
Until now.
Try Our AI Features
Explore what Daily8 AI can do for you:
Comments
No comments yet...
Related Articles
Gizmodo
38 minutes ago
- Gizmodo
Scientists Identify a New Glitch in Human Thinking
Good news, everyone! Scientists at the University of California, Berkeley, have coined a new term to describe our brains being dumb. In a recent study, they provide evidence for a distinct but common kind of cognitive bias—one that makes us reluctant to take the easier path in life if it means retracing our steps. The researchers have named the bias the 'doubling-back aversion.' In several experiments, they found that people often refuse to choose a more efficient solution or route if it requires them to double back on the progress already made. The findings suggest that people's subjective fear of adding more to their workload and their hesitance to wipe the slate clean contribute to this bias, the researchers say. 'Participants' aversion to feeling their past efforts were a waste encouraged them to pursue less efficient means,' they wrote in their paper, published this May in Psychological Science. The 12 cognitive biases that prevent you from being rational Psychologists have detailed all sorts of biases related to digging our feet in when faced with important new information. People tend to stick to the status quo in choosing dinner at a favorite restaurant, for example, even when someone recommends a potentially tastier option. There's also the sunk cost fallacy, or the reluctance to veer off a disastrous path and choose another simply because they've spent so much time or resources pursuing it. The researchers argue that their newly named bias is certainly a close cousin to the sunk cost fallacy and similar biases, but that it ultimately describes a unique type of cognitive pitfall. In their paper, they provide the example of someone whose flight from San Francisco to New York becomes massively delayed early on, leaving them stuck in Los Angeles. In one scenario, the traveler can get home three hours earlier than their current itinerary if they accept the airline's offer of a new flight that first stops in Denver; in the second, the person is instead offered a flight that will also shave three hours off, but they'll first have to travel back to San Francisco. Despite both flights saving the same amount of time, people are more likely to refuse the one that requires going back to their earlier destination, the paper explains (some people might even refuse the Denver flight, but that would be an example of the status quo bias and/or sunk cost fallacy at work, they note). To test their hypothesis, the researchers ran four different types of experiments. The experiments collectively involved more than 2,500 adults, some of whom were UC Berkeley students and others who were volunteers recruited through Amazon's Mechanical Turk. In one test, people were asked to walk along different paths in virtual reality; another asked people to recite as many words starting with the same letter as possible. Across the various tests, the researchers found that people routinely exhibited this aversion. This Is What Your Brain Looks Like When You Solve a Problem In one experiment where people had to recite words starting with 'G,' for instance, everyone was asked midway through if they wanted to stay with the same letter or switch to reciting words starting with 'T' (a likely easier letter). In the control condition, this decision was framed as staying on the same task, simply with a new letter, but in the other, people were asked if they wanted to throw out the work they had done so far and start over on a new task. Importantly, the volunteers were also given progress bars for the task, allowing them to see they would perform the same amount of work no matter the choice (though again, 'T' would be easier). About 75% of participants made the choice to switch in the control condition, but only 25% did the same when the switch was presented as needing to double back. 'When I was analyzing these results, I was like, 'Oh, is there a mistake? How can there be such a big difference?'' said lead author Kristine Cho, a behavioral marketing PhD student at UC Berkely's Haas School of Business, in a statement to the Association for Psychological Science, publishers of the study. Other researchers will have to confirm the team's findings, of course. And there are still plenty of questions to answer about this aversion, including how often we fall for it and whether it's more likely to happen in some scenarios than others. But for now, it's oddly comforting to know that there's another thing I can possibly blame for my occasional stubbornness to take the faster subway train home.
Yahoo
2 hours ago
- Yahoo
Scientists Are Building a Nuclear Device That Could Unveil an Invisible Universe
"Hearst Magazines and Yahoo may earn commission or revenue on some items through these links." Here's what you'll learn when you read this story: Scientists are close to creating a nuclear clock—an ultra-accurate clock that uses a low-energy transition in the nucleus of a thorium-229 atom to keep time. Electrical interference makes atomic clocks unsuited for dark matter detection, but nuclear clocks don't have that problem, and could provide a resolution some 100,000 times better than what we currently have. There's no guarantee that using a nuclear clock will finally find the theoretical perturbations caused by dark matter, but it will help scientists explore a new atomic realm as a part of that never-ending search. Once considered an unusable byproduct of the U.S. nuclear program, thorium-229—an isotope of the silvery-white metal, thorium—could become central to humanity's search for dark matter. Up to this point, scientists have devised massive detectors, surveyed gravitational effects, and studied cosmic radiation in the hopes that it might point to evidence of this elusive substance. Now, researchers are considering whether a nuclear clock powered by the low-energy transitions of a thorium-229 nucleus may work as a new method in the particle hunt. In a new study published in the journal Physical Review X, scientists from Germany, Israel, and Spain explored ways that the unique properties of a nuclear clock could detect the influence of dark matter. Today's most accurate clocks (atomic clocks) rely on the oscillations of electrons between two quantum states to keep time. While highly precise, these clocks are susceptible to electrical interference. Proposed nuclear clocks, which use the nuclei of an atom, are far less impacted by these disturbances. The resonance frequency—the steady swing of nuclei between 'ground' and 'high-energy' states—is typically pretty high, requiring strong radiation to excite the nucleus and produce the 'tick-tock' of a nuclear clock. Thorium-229, however, is special because its resonance frequency is low enough to be excited by modern laser technology, theoretically making a nuclear clock possible. 'When it comes to dark matter a thorium-229-based nuclear clock would be the ultimate detector,' Gilad Perez, a co-author of the study from the Weizmann Institute of Science, said in a press statement. 'Right now, electrical interference limits our ability to use atomic clocks in the search […]. We estimate [nuclear clocks] will enable us to detect forces 10 trillion times weaker than gravity, providing a resolution 100,000 times better than what we currently have in our search for dark matter.' In the past year, labs around the world have made major breakthroughs in developing a thorium-229 nuclear clock, which culminated in a paper published in September of 2024 in the journal Nature. That paper reported an observation of a thorium-229 transition that was millions of times more accurate than previous attempts. 'In a universe made up only of visible matter, the physical conditions and the absorption spectrum of any material would remain constant,' Perez said in a press statement. 'But because dark matter surrounds us, its wave-like nature can subtly change the mass of atomic nuclei and cause temporary shifts in their absorption spectrum […]. We still need even greater precision to develop a nuclear clock, but we've already identified an opportunity to study dark matter.' There's no guarantee that nuclear clocks will end our hunt for dark matter, but they do represent a new atomic frontier that has yet to be explored as part of that endless search. Not so bad for an isotope once considered a mere 'byproduct.' You Might Also Like The Do's and Don'ts of Using Painter's Tape The Best Portable BBQ Grills for Cooking Anywhere Can a Smart Watch Prolong Your Life? Solve the daily Crossword
Yahoo
2 hours ago
- Yahoo
Autonomous robots rappel into lunar caves to test exploration techniques
Future missions to Mars and the moon may involve exploring underground lava tubes. These natural caves could hide signs of life and offer shelter for human settlements. Scientists have now tested whether autonomous robots can handle the task in a real-world setting. The trials took place inside a lava cave on Lanzarote, a volcanic island in Spain's Canary Islands. The location was chosen because it closely resembles the underground structures found on Mars and the moon. Underground shelters in space Lava tubes form when flowing lava solidifies on the surface while molten rock continues moving below. Once the flow stops, long hollow tunnels remain. These structures exist on Earth and have been detected on Mars and the moon. Researchers believe they could protect astronauts from harsh conditions, including extreme temperatures, radiation, and meteorite strikes. They might even host microbial life. Human exploration of these caves is dangerous and costly. Robots offer a safer, cheaper way forward. "A heterogeneous cooperative robot team is a promising approach to address the access and exploration of extraterrestrial lava caves," wrote the researchers in Science Robotics. Robots in the cave The field trials lasted 21 days and unfolded in four stages. First, two rovers scanned and mapped the terrain around the cave entrance. They then used one rover to launch a sensor-packed cube into the opening. This payload created a detailed 3D model of the entrance area. The toughest phase involved both robots working in sync. The smaller rover attached itself to the larger one for a rappel down the cave wall. Once inside, it detached and drove deeper into the tunnel. It managed to travel 235 meters while building a 3D map of the route. These experiments showed that robots could carry out coordinated missions in complex underground spaces. They also proved that 3D mapping is possible in dark, enclosed environments. Hurdles before space missions The Lanzarote tests highlighted technical challenges. Moisture in the cave reduced the accuracy of the ground-penetrating radar. Some mapping sensors experienced interference, and the lack of ground-truth data limited verification. Autonomous navigation also remains a major hurdle. In a real Mars or moon mission, robots would need to operate without human guidance for extended periods. That requires more advanced algorithms and reliable communication between units. Despite the obstacles, the research points toward a future where robotic scouts prepare sites for human bases beyond Earth. Such missions could identify the safest and most suitable locations for long-term stays. The same technology could also support the search for life. If microbial life exists in protected underground environments, these robots could help find it. The findings move scientists closer to answering one of humanity's oldest questions, whether we are alone in the solar system. The study is published in the journal Science Robotics. Solve the daily Crossword
