Last Updated on June 23, 2026 by Staff
For a lot of people espresso is not a cup of coffee, it is something they do every day. Even people who make espresso for a living have trouble with something called “channeling” that can make the coffee taste bad.
Now some researchers from the University of Warsaw have used science to understand how espresso is made. They found out some things about how water moves through the coffee grounds and how the pressure of the water affects the taste.
This could help people who make espresso do a job and make the coffee taste more consistent.
The Coffee Problem
The researchers started by asking a question to people in the coffee business. At a coffee conference in Warsaw a student who studied physics asked the people who made espresso what they wanted to know more about. They all said the thing: they wanted to know about “channeling”.
Channeling happens when hot water goes through the packed coffee grounds. The water going through all of the coffee grounds evenly finds some paths that are easier to go through and it rushes through those areas.
This means that some of the coffee grounds get a lot of water and some do not get enough. This can make the coffee taste bad, sometimes it is too bitter or too sour. Because it is hard to see what is happening when the coffee is being made, people who make espresso have to use trial and error to try to make it better.
The researchers did a lot of tests to try to figure out what was going on. They used an espresso machine that could measure the pressure of the water. They did hundreds of tests to see how the water flowed through the coffee grounds. They wanted to know how the coffee grounds behaved when the water was flowing through them. They also wanted to know if the pressure of the water made a difference in how the coffee tasted. The researchers looked at a lot of data. They found some patterns that they had not seen before. They found out that making espresso is more complicated than they thought it would be.
Pressure Changes
One of the important things they found out was how the coffee grounds behave when they are under pressure. When the pressure is not too high the coffee grounds behave like they should. But when the pressure is very high like it is when you are making espresso the coffee grounds start to change. At first the water flows through the coffee grounds like it should. After a while the coffee grounds start to get compressed and they behave differently. This changes how the water flows through the coffee grounds.
A Hidden Effect
The researchers found out about something called compaction. This means that the coffee grounds get compressed. They start to behave like a special kind of material that is both solid and liquid. When this happens, the way the pressure and the flow of water’re related changes. It is not a relationship anymore, it is more complicated. This means that just because you increase the pressure it does not mean that the water will flow faster or that the coffee will be better. In fact, too much pressure can make the coffee taste bad. The researchers think that this is a discovery that can help people make better espresso. They also made a model that can explain how the pressure and the flow of water are related.
Future Brews
The researchers are not done yet they want to learn more about coffee. They want to see what happens inside the coffee grounds when the water is flowing through them. They are going to use materials and glass beads to make a model that they can see inside. This could help them understand how the water flows through the coffee grounds and how channeling happens. It could also help them make espresso machines and teach people how to make better espresso. For the researchers coffee is not a drink it is a fascinating thing to study. They think that physics can help us understand all kinds of things, something as simple as a cup of coffee. As one of the researchers said, physics is about understanding how things work. Whether you are studying the stars or a cup of coffee it is about figuring out the secrets of the universe. Now thanks to this research we might be able to make a better cup of coffee.