Hario NXAR-5 Coffee Siphon Next: Brewing Science and Art in One

Step inside the Victorian-era laboratory hidden on your kitchen counter, where thermodynamics and a little bit of magic conspire to create the cleanest cup you’ve ever tasted.

It doesn’t hum or beep. It has no screen, no buttons, no programming. Yet, as it comes to life, it commands your full attention. Water in a lower glass globe begins to churn, defies gravity, and climbs a narrow tube into an upper chamber. There, it dances with a cloud of coffee grounds in a turbulent, amber-hued ballet. Then, just as suddenly, the show reverses. The brewed coffee cascades back down, leaving a tidy puck of spent grounds behind.

To watch a siphon coffee maker at work is to witness a piece of theater. It feels less like brewing and more like alchemy. But this captivating device, which looks as if it were pulled from a Jules Verne novel, is not powered by magic. It’s powered by the fundamental laws of the universe. It’s a time-traveling physics engine, a relic from the age of steam that still performs its task with a precision many modern machines can’t match. And by understanding it, you don’t just learn about coffee; you get a tangible feel for the invisible forces that shape our world.

The Parlor Trick That Became a Perfect Brewer

To find the origins of this curious contraption, we must travel back to the 1830s, an era humming with the energy of the Industrial Revolution. Science wasn’t just confined to laboratories; it was a form of public entertainment. In the drawing rooms of London and Berlin, amateur scientists and curious minds engaged in “parlor chemistry,” demonstrating the wonders of electricity, optics, and pressure to astonished guests.

It was in this environment that the vacuum coffee pot was born. Patented first by a Berlin inventor named Loeff, the concept quickly spread, capturing the imagination of engineers and designers like Scotland’s Robert Napier, whose elaborate, flame-powered contraptions became centerpieces of Victorian high society. These devices were the epitome of an age obsessed with mechanism and spectacle. They were a statement: science is not just useful; it is beautiful, and it can live in your home. It was a way to domesticate the power of the steam engine, transforming its raw force into a delicate, aromatic beverage.

A Miniature Steam Engine on Your Countertop

At its core, the siphon operates on a beautifully simple thermodynamic principle that governs the relationship between temperature, volume, and pressure. Think of it not as a coffee maker, but as a tiny, two-chamber steam engine. The entire process is a three-act play.

Act I: The Ascent. The show begins with heat applied to the lower globe—the “boiler room.” As the water heats, it follows Charles’s Law: for a fixed amount of gas, its volume is directly proportional to its temperature. Water molecules, excited by the heat, transform into vapor. This rapidly expanding vapor dramatically increases the pressure inside the sealed lower chamber. With nowhere else to go, this pressure acts like a piston, pushing the hot water up the siphon tube and into the upper “brewing chamber.”

Act II: The Stasis. Here, a crucial part of the process unfolds. The coffee grounds are fully and evenly saturated with water that is kept at a remarkably stable, near-ideal brewing temperature (typically between 195-205°F or 90-96°C). Unlike pour-over methods where the water temperature can fluctuate as it’s poured, or drip machines with their inconsistent heating, the siphon creates a controlled environment. This full immersion at a constant temperature allows for a deep and uniform extraction of the coffee’s soluble flavor compounds.

Act III: The Descent. Once the heat is removed, the final, most dramatic act begins. The water vapor in the lower chamber cools rapidly, condensing back into liquid. This phase change causes a sudden and massive drop in pressure, creating a partial vacuum. The atmosphere outside the brewer now pushes down on the coffee in the upper chamber, forcing it through the filter and back into the lower globe. The power of this vacuum is astonishing, a gentle cousin to the same atmospheric force demonstrated in the 17th century by Otto von Guericke’s Magdeburg hemispheres—the two copper halves that sixteen horses couldn’t pull apart. This vacuum pull is what makes the filtration so quick and efficient, leaving behind almost no sediment.

The Invisible Hero: Glass That Bends the Rules

This entire thermal drama of rapid heating and cooling would be impossible without a material that can withstand such abuse. Early siphons were fragile and prone to shattering. The modern incarnation of this brewer, exemplified by the elegant craftsmanship of a company like Japan’s Hario, owes its existence to a late 19th-century scientific breakthrough: borosilicate glass.

Invented in the 1890s by German glassmaker Otto Schott, this wasn’t just any glass. By adding boron oxide to the silica mix, Schott created a material with a very low coefficient of thermal expansion. In simple terms, it barely expands when heated or contracts when cooled. This remarkable stability allows it to resist thermal shock—the stress that shatters a cold glass when hot water is poured into it. This invention, which first found its home in laboratory beakers and industrial piping under the name Pyrex, is the unsung hero that allows the siphon to perform its thermodynamic dance safely and reliably on our kitchen counters.

The Taste of Science

So, what is the ultimate result of all this physics and material science? The proof is in the cup. The flavor profile of siphon-brewed coffee is renowned for two distinct qualities: exceptional clarity and a surprisingly full body.

The clarity comes from the combination of a stable, high-temperature extraction and the hyper-efficient vacuum filtration, which pulls the liquid through the filter (often cloth) so cleanly that virtually no fine particles, or “silt,” make it into the final brew. This lack of sediment allows the more delicate, bright, and acidic notes of the coffee to shine through without any muddying bitterness.

At the same time, because the cloth filter allows the coffee’s natural oils to pass through—oils that paper filters often absorb—the coffee retains a rich, velvety mouthfeel and a full-bodied character. It’s a remarkable achievement: the full flavor extraction of a French press with the pristine cleanliness of the most meticulous pour-over. It is the taste of controlled, intentional science.

The next time you push a button on a pod machine, take a moment to remember this elegant engine. It’s a reminder that sometimes, the most sophisticated technology isn’t the newest, but the one that most perfectly embodies a timeless principle. The siphon coffee maker is more than a tool; it’s a conversation with the past, a tangible piece of scientific history, and a beautiful demonstration that in the quest for the perfect cup, the laws of the universe are the ultimate barista.