The Crazy Evolution of Coffee Filter Paper: How Filter Choice Changes Pour Over Coffee Flavor

 When it comes to coffee extraction—whether it's espresso or pour-over—there’s one thing you simply can’t avoid: the filter paper.

This small sheet of paper has quietly evolved over the past few years alongside the technological development of specialty coffee. In fact, its evolution has been so dramatic that the word “crazy” might not be an exaggeration. This “craziness” includes innovations in materials, upgrades in functionality, and of course, some pretty crazy price tags as well—haha.

Today, I’d like to talk about why filter papers in coffee extraction keep evolving. What exactly are people pursuing when they aim for the ultimate cup of coffee? And what role can filter paper play in shaping the final result? Let’s dive into the “crazy evolution” of coffee filter papers.

Different filter papers vary in density, thickness, structure, and permeability, and these factors directly determine the flow rate. Flow rate, in turn, affects coffee extraction, flavor, and mouthfeel.

Filter paper is no longer just a simple barrier separating coffee grounds from water, nor is it merely about achieving a cleaner cup. Today, it has moved far beyond its basic function and plays a significant role in shaping the extraction process.

Under the philosophy of precise and controllable brewing, filter papers can now be chosen specifically for different roast profiles or processing methods, allowing more targeted brewing experiments. By selecting different types of filter paper, brewers can effectively improve clarity, sweetness, and roundness in the cup.

Filter papers have evolved from simple pulp-based materials into products with carefully engineered density, fiber structure, permeability, and even hydrophobic properties. Their impact is quite noticeable because they introduce a meaningful variable into the brewing process.

During this evolution, several brands have become particularly representative—especially those that focus on producing functional filter papers. One of the most iconic examples is Sibarist. I’ve previously written about many of their products, from their early fast-flow filter paper designed for the Hario V60 to their later DUAL CHAMBER layered filters.

Another example is CAFEC, which produces filter papers designed for different roast levels. Then there’s KINTO with its well-known silky slow-flow filter papers.

All of these filter papers share one key characteristic: they help baristas control the flow rate through the material’s texture and structural properties.

And yes—flow rate control is a crucial factor in coffee extraction. Filter paper may seem like a minor variable, but its impact is clearly visible and perceptible in the final cup.

It influences how water flows through the coffee bed and controls how compounds such as oils, sugars, and acids enter the final brew. This directly affects the mouthfeel and flavor balance.

Let’s take CAFEC filter papers as an example.

For light roasts, the recommended filter has a thickness of 0.15 mm, making it the thinnest of the three. The inner surface has no crepe texture, which results in a smaller internal surface area. Coffee fines attach to this small area, leaving fewer channels for water flow, causing water to accumulate inside the filter.

During brewing, this slows down the flow rate and allows more aromatic compounds to develop. Meanwhile, the crepe texture on the outer side allows the brewed coffee to flow out smoothly. The higher density of the paper also helps prevent fine particles from passing through, ideally producing a cup that is aromatic and clean.

Next is the T-90 filter, designed for medium to dark roasts, with a thickness of 0.28 mm, making it the thickest of the three.

Both the inner and outer surfaces feature crepe textures, creating double-sided creping that allows water to flow most smoothly. Among the three filters, it also provides the largest surface area and relatively lower density. Even if fines attach to the filter surface, the flow rate remains stable.

The goal here is to produce a balanced and full-bodied flavor, enhancing both sweetness and richness.

The T-83 filter, designed for dark roasts, has a thickness of 0.22 mm, placing it in the middle in terms of both thickness and density. It also features double-sided creping, but with a unique design: the crepe height is intentionally kept lower.

In other words, most of the crepe structure is concentrated closer to the bottom of the filter near the dripper’s outlet. During the first half of brewing, when fewer fines have accumulated, water flows relatively smoothly. In the later stage, as more fines attach to the filter, the flow slows down. This helps promote a stronger body and enhanced sweetness in the final cup.

It’s fascinating, isn’t it? Even such a small piece of paper can have a significant impact.

Thinking back 10 or 15 years ago, people were mostly debating whether to buy bleached filter paper or natural (unbleached) filter paper. Today, filter paper selection has become far more multidimensional. Many products are now designed with specific functions to match particular brewing devices or coffee bean characteristics.

This evolution is a natural result of the continuous advancement of brewing equipment, as well as the increasing diversity of coffee processing and roasting techniques.

Flavor compounds in coffee dissolve at different rates. Some extract quickly with hot water, while others require longer contact time.

Based on this principle, differences in filter paper permeability can help extract specific combinations of soluble compounds. For example, the classic FAST filter paper from Sibarist is designed to increase extraction yield within a shorter brewing time. It emphasizes compounds extracted early in the brewing process, highlighting acidity, complexity, and flavor vibrancy.

So when choosing filter papers for everyday brewing, what basic principles should we follow?

Here are a few general guidelines. Of course, they’re only references—you should always adjust based on your own brewing practice and flavor preferences.

From a flavor perspective, if you enjoy delicate, floral, or high-acidity profiles, a fast-flow filter is often a good choice. It helps maintain clarity, aromatic complexity, and a lighter mouthfeel, making the coffee feel more elegant and refined.

On the other hand, if you prefer coffee with strong body and noticeable sweetness, you might choose a denser filter paper and pair it with a longer extraction time to build deeper sweetness and a richer texture.

Another factor to consider is your brewing device.

If you’re using a dripper that tends toward immersion-style extraction, such as a slow-drip system, pairing it with a faster-flow filter paper can help prevent over-extraction while maintaining clarity and flavor definition.

You can also take the coffee processing method into account.

Washed coffees usually contain less surface oil because most of the oils remain locked within the bean’s cellular structure. As a result, they often require a longer extraction time to release more oils and aromatic compounds.

Natural (sun-dried) coffees, on the other hand, tend to have higher surface oil content and release soluble compounds more quickly. In such cases, pairing them with a faster-flow filter can work well.

That said, nothing replaces hands-on experimentation.

Try brewing the same coffee with the same equipment but using different types of filter papers. Pay attention to how the mouthfeel, clarity, and balance of the coffee change.

You might be surprised by how much difference that small piece of paper can make—and hopefully, you’ll have some interesting brewing insights to share with others as well.

Roasting Coffee Beans with a Hand-Cranked Popcorn Machine: Clever Hack or Dangerous Mistake?

 Not long ago, I came across a video online showing someone roasting coffee beans using a traditional hand-cranked popcorn machine—the kind we used to see on the street when we were kids, the one that would suddenly go BOOM behind you without warning. Honestly, that thing alone was childhood trauma for many of us. Of course, when used for coffee beans, there wouldn’t be that final explosive step. From a purely theoretical standpoint, this method does seem somewhat feasible. Still, I find it extremely unreliable in practice. So today, I want to take a closer, more serious look at this idea.

Traditional hand-cranked popcorn machines are actually somewhat similar to hand-mesh coffee roasting. Both rely on an external heat source—usually an open flame—to heat a sealed metal drum, allowing the contents inside to undergo physical and chemical changes. By manually cranking the handle, the beans can be agitated so they heat more evenly, reducing the risk of localized scorching. In principle, this isn’t all that different from how professional coffee roasters work. From a purely “can it cook the beans” perspective, yes—it can roast green coffee beans to a drinkable state. But to me, this method, much like hand-mesh roasting, comes with far too many uncontrollable variables and places very high demands on the operator’s skill. One small mistake, and things can go south very quickly.

As we all know, coffee roasting is a precise science. Different beans and different roast levels—light, medium, dark—require careful control of the temperature curve and the final endpoint temperature. With a popcorn machine, the temperature is neither measurable nor controllable. This makes it very easy to end up with beans that are burnt on the outside and underdeveloped on the inside—or worse, completely charred. Beyond temperature instability, timing is also extremely difficult to manage. Coffee roasting requires holding beans at specific temperatures for specific durations to properly develop flavor. A popcorn machine simply cannot provide that level of control. Roast time becomes entirely dependent on personal experience, and with so many variables involved, the outcome is highly random.

There’s also a critical safety concern that deserves special attention. When heating corn, popcorn machines build up internal pressure until the final “pop.” While coffee beans won’t explode like corn, they do release a large amount of smoke during roasting—mainly carbon dioxide and vaporized oils. If exhaust is insufficient, pressure can still build up inside a sealed container, creating a real risk of rupture or even explosion. On top of that, coffee roasting produces a lot of chaff, which is highly flammable. Professional coffee roasters are equipped with robust exhaust and cooling systems to handle this. A traditional hand-cranked popcorn machine, operated over an open flame in an open environment, dramatically increases the risk of chaff ignition or internal flare-ups.

Even if all of these risks were somehow managed through experience, roasting consistency would still be a major issue. Uneven roasting would result in inconsistent bean color, muddled flavors, and a pronounced smokiness in the cup. It would be nearly impossible to develop the elegant acidity, sweetness, and floral or fruity notes that make coffee enjoyable. Instead, you’re far more likely to get unpleasant defects such as smoky, burnt, rubbery, or bitter flavors. I’ve actually had coffee from small shops that intentionally use hand-mesh roasting—perhaps precisely for that smoky character. But achieving clean, pleasant flavors with such traditional methods is incredibly difficult. On top of that, post-roast cooling is absolutely crucial. A popcorn machine cannot cool beans quickly, allowing residual heat to continue roasting them and trapping dull, baked flavors inside.

So when you see videos like this online, I strongly advise against imitating or experimenting with them out of curiosity. Many content creators do these “wild” methods simply to make entertaining videos or chase traffic. In reality, using a traditional popcorn machine to roast coffee is both dangerous and inefficient, and it’s almost impossible to produce a truly good cup of coffee this way. If you really want to experiment with hands-on roasting, I’d recommend starting with a proper coffee roasting hand mesh instead. That’s how many enthusiasts begin. It’s inexpensive, but it requires practice—and good ventilation and fire safety are essential.

Finally, for anyone thinking about getting into coffee roasting: the real joy lies in fine control over flavor. And that inevitably means using the right tools. For your own safety—and for a genuinely good cup of coffee—it’s worth choosing a more appropriate and professional approach.

What Makes a Great Coffee Roaster? A Deep Dive into the Art & Science of Coffee Roasting

 Among coffee professionals, there is a group of true “behind-the-scenes heroes.” They may not be great talkers, many of them lean toward being introverts, and they tend to work with rigor, precision, and an almost obsessive attention to detail and data. In my eyes, they are among the most technically skilled people in the coffee industry: coffee roasters.

If I had to sum up their work in one sentence, it would be this:
“I am not the creator of flavor—I am a carrier of flavor.”
They are the ones who allow every coffee drinker to experience the unique character and terroir of different origins. In that sense, roasters play an irreplaceable role.

Looking back, I’m surprised that despite nearly ten years of daily writing, I’ve never written a dedicated piece about coffee roasters. Recently, as I’ve been testing beans from different roasters, I’ve found that I can genuinely sense their thinking through their roasting styles. This quiet, almost invisible form of dialogue has deepened my appreciation and respect for roasters—and that’s why I want to share my personal definition of what makes an outstanding one.

In the early years, whenever I attended coffee expos, I loved wandering through different halls to watch competitions. I’d marvel at the complexity of latte art designs, or cheer for the confident performances in barista championships. The atmosphere was always intense and electrifying. But when it came to roasting competitions, the scene was entirely different—almost silent. Roasters stood quietly by their machines, roasting beans, surrounded only by the rich, toasty aroma of freshly roasted coffee. Sometimes I couldn’t help but think: roasters are truly a group of people who can endure solitude.

They must integrate technical skill, sensory acuity, scientific thinking, and artistic creativity. Among all coffee-related roles, roasting may be the one that demands the most comprehensive set of abilities.

From my perspective, a solid foundation of technical knowledge is essential for any roaster. They need to be deeply familiar with the flavor profiles of different origins, varieties, and processing methods, and understand how physical characteristics such as green bean density and moisture content affect roasting outcomes. At moments like this, the old saying “Master math, physics, and chemistry, and you can go anywhere” suddenly feels very real—haha.

Roasters must also have a strong grasp of heat transfer (conduction, convection, radiation), the Maillard reaction, caramelization, and other physical and chemical processes. They need to adjust heat curves according to bean characteristics and master the logic and behavior of different roasting machines, whether direct-fire, semi-hot-air, or electric.

Beyond these technical foundations, roasters also need skills similar to those of baristas—most importantly, sharp sensory evaluation abilities. Through cupping—assessing dry and wet aroma, acidity, sweetness, body, and more—they must accurately judge roasting results and build a reliable flavor memory library.

Roasting one good batch doesn’t mean much. True mastery lies in consistency—producing good results batch after batch. We often judge a roaster by whether different batches of the same coffee taste noticeably different, which can even affect brewing parameters downstream. This shows just how critical roasting consistency really is. Developing standardized roast profiles that ensure stable flavor across batches while meeting commercial production demands is one of the core competencies of an excellent roaster.

If everything above represents “hard skills,” then the following are the “soft skills” that truly differentiate roasters at a higher level. Whether baristas or roasters, when working with a non-standardized product that people consume, the ability to flexibly apply knowledge in real-world situations becomes crucial. Being overly dogmatic or ignoring the relationships between variables can turn an inherently exploratory craft into something rigid and stagnant.

Many outstanding roasters seem to enjoy solitude—or at least quiet focus. They must possess patience and deep concentration, enduring repeated testing and adjustment. It may take dozens of trials to find the optimal roast profile for a single coffee. They spend long hours monitoring the roaster, remaining highly sensitive to details such as first crack sounds and color changes.

Whenever I visit roasting facilities and happen to see a roaster at work, even watching through a glass wall, I can’t help but feel that the end of roasting is… loneliness. It’s truly demanding work.

That said, roasters also need strong communication and collaboration skills. Some younger roasters may fall into the trap of working in isolation—focusing solely on roasting without engaging with the outside world or paying attention to industry trends. That’s a dangerous path.

Data-driven decision-making—using roast curves and cupping scores—combined with the courage to experiment with new processing methods and blending strategies is essential. With innovative processing techniques constantly emerging, roasting faces new challenges all the time. Staying informed about industry trends and understanding shifts in consumer taste preferences should be a conscious, ongoing habit.

Another crucial scenario is custom roasting. Many roasters work closely with partners to create tailored roast profiles. This customization isn’t just about exclusive blends or unique roast curves—it’s about understanding brand positioning, target flavor profiles, and balancing cost, efficiency, and flavor. In commercial roasting, profitability must also be considered. Creating a distinctive roasting style that gives a brand a recognizable identity requires roasters to be adaptable, business-aware, and committed to continuous learning.

In fact, many roasters are also “coffee hunters,” traveling to origin countries, working directly with farms, and participating in quality control from cultivation through processing.

An outstanding coffee roaster is both a scientist and a craftsman. They connect producers and consumers, serving as a core creator within the coffee value chain. Roasting is never just about making beans “done.” It is a long-term pursuit that demands dedication, passion for flavor, and a commitment to constant refinement.

This piece reflects only my personal perspective and appreciation. I can’t possibly list all the qualities that make roasters exceptional. But I do know this: they deserve far more recognition. When we taste a cup of coffee, we should try to sense the quiet effort and unspoken care of these behind-the-scenes heroes.

To all the coffee roasters out there—you are truly amazing. Thank you for being here, for filling my life with good coffee, and for enriching it in ways that often go unseen. 

Why −86°C Ice Cup Dirty Coffee Is the Hottest Specialty Coffee Trend Right Now

 The first time I tried a Dirty coffee served in an ultra-low-temperature ice cup was back in 2023, at UNCLE SHU Coffee in Binjiang, Hangzhou. It was my first real encounter with that striking “hot-meets-cold” contrast, and the experience left a strong impression.

Dirty coffee is something most coffee lovers in China are already familiar with. It’s fairly common in cafés across Asia, yet you’ll rarely find it in Europe or the U.S. At its core, a Dirty is simple: ice-cold milk topped with hot espresso. This collision of temperatures creates a dramatic, almost theatrical drinking experience that many people love.

In recent years, however, a new trend has taken things to the extreme—using ice cups chilled to −86°C to make Dirty coffee. Compared with a traditional Dirty, which usually uses milk and a cup chilled to around 4°C, a −86°C ice cup paired with espresso at roughly 65–70°C creates a temperature difference of more than 150°C. This extreme contrast delivers a sharper, more intense sensory experience and a longer-lasting cold sensation that ordinary Dirty coffees simply can’t achieve.

One unique result of this method is the formation of a thin layer of “milk frost.” When cold milk is poured into an ultra-frozen cup, a delicate layer of frozen milk instantly forms along the inner wall of the cup. Visually, you’ll often see white vapor rising from the glass, which adds a strong sense of drama. In terms of texture, it introduces an extra layer of enjoyment—you can even scoop up this milk frost with a spoon after finishing the coffee.

The −86°C cup also functions as a powerful “cold reservoir.” Even in the peak of summer, it can keep a Dirty coffee cold for a remarkably long time, significantly slowing down the warming of both the milk and the espresso. Every sip stays refreshingly cold. From a presentation standpoint, this method is also a win. Many customers are quite obsessed with the layered look of a Dirty coffee, and the extremely cold cup helps preserve that separation. The cold cup walls lock in the espresso’s crema and slow the mixing of coffee and milk, allowing the layers to remain visible for much longer.

There’s also a clear marketing angle to all of this. Cafés often highlight the number “−86°C” very prominently. It sounds extreme, memorable, and instantly sparks curiosity. Seeing such a number alone is enough to make people want to try it. Many customers even film the entire process—from baristas wearing gloves and using tongs to retrieve the cup, to explanations of how to drink it quickly. This ritualized presentation not only enhances the sense of occasion, but also strongly encourages social sharing.

That said, I couldn’t help but wonder: why −86°C specifically? What would happen at other temperatures?

After looking into it, the differences become clearer. A standard frozen cup is usually kept at around −18°C, the typical temperature of a home freezer. This is already a common and effective method for Dirty coffee—it increases the temperature contrast, extends the cold sensation, and helps maintain layering. A chilled cup, stored in a refrigerator at about 4°C, can also be used. In this case, the cup temperature matches that of the cold milk, creating clear layers and a noticeable hot-cold contrast, but the cooling effect is short-lived. After about five minutes, the drink begins to approach room temperature. Finally, there’s the room-temperature cup option. While not ideal, it’s still workable—especially at home when you’re just making a casual daily cup. The layering can still look decent, but the hot-cold contrast is much weaker, and the milk warms up very quickly. If you don’t drink it fast, the flavors blend too much and the experience suffers.

Interestingly, many professional baristas point out that −86°C isn’t a strict or precise requirement. Rather, it represents the lowest stable temperature that commercial deep freezers can reliably reach. In real-world café operations, frequent opening and closing of the freezer means the cup temperature often fluctuates between −60°C and −86°C. As long as the cup is cold enough to create milk frost and provide extreme cooling, the core experience remains intact.

For those who haven’t tried this style of Dirty yet, there’s one concern worth addressing: it won’t freeze or damage your mouth. Once the hot espresso and cold milk are poured in, the liquid temperature is actually well above 0°C. What you’re really experiencing isn’t danger—it’s contrast, precision, and a carefully crafted sensory spectacle.

Why Cafés Filter Crema From Americanos | Clean Taste vs Traditional Espresso

 This question is something I’ve noticed quite frequently over the past year while café hopping. Of course, it’s not a new topic for me—I’ve already touched on it multiple times in previous articles. Personally, I’ve encountered it so often that I’ve almost become “desensitized” to the idea of filtering crema from an Americano. But if we take a more rational step back, the reason many cafés now promote over-extraction–style Americanos is fairly clear: they’re chasing a cleaner, more stable, and smoother mouthfeel, while trying to avoid unpleasant flavors.

From my point of view, over-extraction–based Americanos and traditional “espresso + water” Americanos follow fundamentally different extraction and brewing logics. In that context, removing the crema can be a 1 + 1 > 2 kind of optimization. However, if it’s just a standard espresso shot that’s brewed normally, then filtered for crema, and only afterward diluted with water, I personally feel it would be better to leave the crema intact. After all, that crema is the soul of the espresso.

So why do so many cafés filter out the crema when serving an Americano? It’s undeniably a widespread and discussion-worthy phenomenon in today’s specialty coffee scene. By “crema,” I’m referring to the oily substances in coffee beans (along with some ultra-fine coffee particles). Strictly speaking, this isn’t true oil. Rather, it’s a stable, oil-like foam formed through emulsification under high pressure—what we commonly call crema.

Not long ago, I talked about how crema is often considered the soul of espresso, and I believe many people still hold that view. In traditional Italian coffee culture, a perfect espresso is expected to have a thick, fine, brown crema on top. It’s seen as a marker of freshness and successful extraction, contributing to a richer mouthfeel and longer-lasting aroma. In some evaluation systems, the color and thickness of the crema are even key scoring criteria. What we’re seeing now is, to some extent, a departure from that tradition—a redefinition of how we understand espresso’s role as a base in beverages like the Americano.

I think this shift also reflects how people’s flavor preferences have evolved. The industry has gradually moved away from the classic pursuit of “intense, bitter, and heavy-bodied” coffee toward a preference for “clean, sweet, and transparent” flavors. Under this new paradigm, crema can sometimes work against the desired profile. Crema contains a relatively high concentration of compounds such as quinic acids, which can introduce sharp, lingering bitterness and astringency.

This becomes even more apparent now that many espresso programs favor light or light-medium roasts, aiming to highlight fruity notes, floral aromas, and bright acidity even in espresso. In such cases, the bitterness and harshness associated with crema can easily overshadow the coffee’s elegant origin characteristics.

In China, drinking espresso straight is still relatively uncommon, but I’d still like to point out one thing: if you are going to drink espresso on its own, it’s important to stir the crema thoroughly into the liquid before drinking. Otherwise, the crema can actually detract from the overall mouthfeel. Also, the flavor of crema changes over time. Fresh crema tastes very different from crema that has been sitting for a few minutes—it oxidizes and breaks down, becoming less pleasant. In that sense, the problem isn’t always the crema itself, but sometimes the way we approach drinking it.

Another key consideration is consistency. The amount of crema varies from shot to shot, which means each Americano can look slightly different and deliver a subtly different initial taste. If there are roasting defects, crema can further amplify undesirable flavors such as burnt bitterness, smokiness, or rubbery notes. By filtering out the crema, cafés can make every cup look clear and uniform, while also reducing the amplification of flavor flaws in the finished Americano.

On top of that, cafés today are highly visual spaces. The appearance of a drink matters. When espresso is poured directly into water, the crema floats on the surface, and that foamy layer isn’t always visually appealing. Sometimes it breaks apart awkwardly or clings to the sides of the cup. To many consumers, that’s the very definition of “not photogenic.” It’s only natural, then, that cafés would try to avoid this and gradually adopt crema filtration as a standard practice.

Seen this way, filtering crema from an Americano is essentially a deliberate choice—a form of flavor selection and mouthfeel optimization. It also introduces a new layer of dialogue at the point of ordering. If you’re someone who loves crema, it’s worth asking whether the café filters it by default. And if you enjoy the richness and heavier body that crema brings, you may want to ask the barista not to filter it out.

In the end, there’s no right or wrong when it comes to flavor and texture—only personal preference. In that sense, the Americano has gained yet another dimension of choice. And perhaps, on a deeper level, this trend reflects a more nuanced understanding of quality within the industry, as well as a growing respect for the diversity of consumer tastes.

Why Coffee on Airplanes Tastes So Bad (And Why Espresso Machines Aren’t Allowed Onboard)

 I’ve talked before about “coffee on airplanes,” and anyone who’s been on a long-haul flight knows the feeling—at some point, you just want a decent cup of coffee to stay awake. Unfortunately, what you usually get onboard is instant coffee, to the point where most people have completely given up hope.

For a long time, I assumed this was simply airlines trying to cut costs, or maybe a result of limited cabin space that made it impossible to install proper coffee machines. Either way, I never felt I had a truly convincing explanation. Carrying that bias with me, I eventually started digging into the topic. After looking into the details, I finally found some solid reasons that answered a question I’d wondered about for years. So today, let’s talk about why it’s basically impossible to brew fresh coffee with a coffee machine on an airplane.

I’m sure many people share this professional—or at least emotional—curiosity. The idea of sipping a freshly brewed coffee at 35,000 feet sounds incredibly pleasant. But the reality is that the absence of onboard espresso machines isn’t due to a single limitation. It’s the result of multiple factors working together. Once you understand them, instant coffee on your next flight suddenly feels a bit more forgivable—at least in theory.

The first and most decisive factor is safety. High-quality espresso machines require enormous bursts of power to heat their boilers and drive high-pressure pumps. Aircraft electrical systems are designed primarily for avionics and low-power passenger devices like phones and laptops. They simply aren’t built to handle the massive power draw of commercial espresso machines. Forcing such equipment into the system could cause circuit overloads, power failures, or even fire hazards.

On top of that, espresso relies on high-pressure extraction. Although aircraft cabins are pressurized, the pressure still corresponds roughly to an altitude of 2,000–2,500 meters (about 6,500–8,200 feet). In this environment, water boils at a lower temperature—around 90°C (194°F). That alone affects extraction efficiency and leads to subpar flavor. More critically, the pressure difference between the inside of an espresso machine and the lower ambient cabin pressure places extreme demands on seals and internal components, significantly increasing the risk of leaks or mechanical failure.

Espresso machines also involve heating elements, hot water, and high-temperature steam—all of which are inherent fire risks. In flight, a fire is far more dangerous and far harder to manage than on the ground. Add turbulence into the mix, and the risk increases even further. A heavy machine filled with near-boiling water and pressurized steam would have to be secured perfectly. If it tipped over, the consequences could be severe. The commercial espresso machines we see in cafés simply aren’t designed with high-altitude operation or in-flight conditions in mind, which makes them fundamentally unsuitable for aircraft use.

Then there’s the very practical issue of time and service efficiency. Even on long-haul flights, cabin crews may need to serve hundreds of passengers. Pulling a single espresso shot takes only a few dozen seconds, but the full process—grinding, dosing, tamping, extracting, and cleaning—takes much longer and requires specialized training. There’s simply no way to spend several minutes making coffee for each passenger without severely slowing down overall service. Even if this were limited to first-class cabins, it still wouldn’t solve the safety and technical issues mentioned earlier.

Space and weight are also critical considerations. Every inch of cabin space and every kilogram onboard directly affects fuel efficiency. A commercial espresso machine, along with a grinder, water connections, and drainage, would take up a significant portion of galley space. By comparison, the hot water boilers currently used on aircraft, along with pre-ground coffee or coffee packs, are vastly more efficient in both space and weight.

Water quality is another factor. While aircraft water tanks meet hygiene standards, their mineral content and taste differ from properly filtered water used in cafés. This alone can negatively affect coffee flavor. Installing a dedicated water filtration system just for coffee would be highly impractical.

Even if we take a step back and imagine that an airline somehow managed to serve you a café-quality espresso in the air, you still probably wouldn’t experience its true flavor. This brings us to the passenger’s perspective: why does coffee taste worse on a plane in the first place? Altitude changes how we perceive flavor. Cabin air reduces our sense of smell, and taste sensitivity can drop by as much as 30%. Acidity becomes harder to detect, sweetness is muted, and bitterness tends to stand out more.

High altitude also brings other physiological effects—bloating, pressure changes, dehydration, and reduced energy levels—all of which influence sensory perception. On top of that, the lower cabin temperature means hot coffee cools down faster than it would on the ground, further degrading the experience.

That’s why the most common coffee you see onboard today is drip coffee. Flight attendants typically load large bags of pre-ground coffee into specialized drip machines on the ground, add hot water, brew a full pot at once, and then serve it to passengers. Some airlines take things a step further by using coffee capsules. A few premium carriers have introduced capsule systems similar to Nespresso. These machines are simpler in structure, require less power, and are easier to operate, while delivering more consistent flavor than drip coffee. Even so, they’re specially designed or rigorously certified for aviation use and differ from standard ground-based models.

Some people might ask: if espresso is impractical, what about hand-brewed pour-over coffee? In reality, the same issues apply. Even without a large machine, pour-over still requires grinding, dedicated workspace, and extra time. From a service perspective, it’s simply not a viable way to quickly serve passengers during a long flight.

When you look at all of this together, it becomes much easier to understand why good coffee is so hard to come by in the air. The problem isn’t that it’s technically impossible—it’s that safety, efficiency, and economics all outweigh the pursuit of better flavor. At 35,000 feet, safety and reliability will always come first. As for truly good coffee, it’s probably best enjoyed after landing, when you can seek out a local specialty café and let your taste buds work the way they’re meant to.

ISSpresso: How the World’s First Espresso Machine Made Coffee Possible in Space

 As coffee continues to grow in popularity, the places where people enjoy it are no longer limited to homes or cafés. Today, coffee can be made almost anywhere—yes, even in outer space. That’s right: astronauts on space missions can enjoy coffee too.

This may not sound like breaking news. In fact, it became possible more than a decade ago. However, relatively few people know the story behind it. So today, let’s take a closer look at the world’s first espresso machine designed for space: ISSpresso.

Back in 2015, the Italian Space Agency partnered with Italian coffee company Lavazza to develop the world’s first espresso machine for the International Space Station. The machine was named ISSpresso.

In space, due to microgravity, liquids don’t flow the way they do on Earth, making something as simple as drinking coffee extremely challenging. For many years, astronauts could only consume instant coffee squeezed out of pouches—hardly a pleasant or satisfying experience. ISSpresso fundamentally changed that by dramatically improving both drinkability and flavor.

After all, for Italians, a good cup of coffee makes everything better—and astronauts are no exception.

One of the greatest challenges in designing ISSpresso was making espresso in a microgravity environment. Traditional espresso extraction on Earth is closely tied to gravity, or at least influenced by it. Successfully brewing coffee under microgravity conditions became a fascinating and meaningful experiment.

Beyond coffee itself, ISSpresso also created valuable opportunities to study fluid dynamics in microgravity—specifically how liquids (both pure and mixed) behave under high pressure and high temperature in space.

To overcome challenges related to microgravity, pressure, and safety, ISSpresso was built using specially designed sealed bags and steel tubing. Development took 18 months and went through four different prototypes before arriving at the final version.

The first prototype, known as the 2-D model, focused on hydraulic and pneumatic systems. The second, called the Elegance model, was developed to test mechanical functionality and align components with those used in the flight unit. The third version, the ground model, was nearly identical in function to the flight model and underwent extensive testing.

The final Protoflight model—the actual flight unit—integrated the best technical solutions from all previous versions. Its internal and external structures were designed and tested to withstand the loads experienced during launch aboard the SpaceX CRS-6 spacecraft.

Compared to commercial espresso machines on Earth, ISSpresso is heavier and far more complex. This is mainly due to material choices and additional safety systems required for space use.

The machine weighs nearly 20 kilograms (with dimensions of 43 × 42 × 36 cm). Its hydraulic circuit uses steel piping instead of plastic, allowing it to withstand operating pressures of up to 400 bar. The brew head is designed to minimize residual water after extraction and is equipped with micro-switches that prevent high-pressure hot water leaks if the brew head fails to close properly.

Before ISSpresso, astronauts only had access to instant coffee—thick, paste-like beverages squeezed from pouches, with flavor that left much to be desired. ISSpresso dramatically improved coffee quality in space and offered multiple beverage options, including:

• Espresso (30 ml)

• Long espresso / lungo (60 ml)

• Hot drinks such as tea or broth (120 ml)

The machine also includes a 60 ml rinse cycle to clean the hydraulic system after use.

To operate ISSpresso, astronauts use a NASA-standard beverage pouch along with specially designed coffee capsules. The operation is similar to using a traditional espresso machine and requires no special training.

Once the water container is properly installed, the astronaut inserts a coffee capsule into the top opening, closes the hatch, selects the desired beverage, and connects the drink pouch to the adapter. Brewing begins at approximately 75°C, while replicating the extraction pressure of ground-based espresso machines.

The water container and beverage pouch connectors are compatible with the space station’s drinking water distribution system, ensuring seamless integration.

To drink the coffee, astronauts use a specially designed zero-gravity espresso cup, which relies on capillary action to draw liquid into the mouth—making it possible to enjoy espresso even in space.

It’s remarkable that humanity’s pursuit of a truly good cup of coffee could help advance space technology. ISSpresso not only satisfied astronauts’ taste buds but also stands as an impressive engineering achievement—further proving that coffee is deeply embedded in human culture.

Key Milestones of ISSpresso

• April 14, 2015: The ISSpresso flight model was launched to the International Space Station aboard SpaceX CRS-6

• May 3, 2015: Astronaut Samantha Cristoforetti enjoyed the first espresso in microgravity

• December 14, 2017: The ISSpresso mission concluded, and the machine returned to Earth via SpaceX CRS-13