This is why baristas are not to blame for bad espresso

Every espresso shot begins with the same two ingredients: coffee and water. But while the coffee changes from origin to origin, roast to roast, the water seems constant. It flows, heats, and disappears into the puck. We treat it as a passive player.

That is a mistake.

Espresso is 93 % water. The rest is flavor compounds pulled from the coffee. So when a shot tastes sour, flat, or wildly different from the one before it, the first thing we should question is not the barista. It is the water.

Yet we do not. We change the grind. We adjust the dose. We look at the roast date. We blame the person behind the machine.

But if your water is unstable, every other variable becomes unpredictable. That is because water is not just a carrier. It is the main ingredient and a volatile one at that.

PS: this article assumes you already have great quality water feeding your espresso machine.

What espresso machines are really doing

A typical espresso machine heats water to 90 to 96 degrees Celsius and sends it through packed coffee at around nine bars of pressure. In about 30 seconds, you get a concentrated shot with crema.

That is the theory. But it hides what is really happening.

Inside the machine, water and steam interact in a closed, high pressure environment. Every time you pull a shot, cooler water enters the boiler. Steam builds, collapses, and condenses. Pressure shifts. Flow changes. Temperature dips. All of these affect the water before it even touches the coffee.

And this is where the real inconsistencies begin.

Understanding water density

Water density is a measure of how tightly its molecules are packed. It changes with temperature and pressure. The hotter the water, the less dense it becomes. The cooler it is, the denser it gets.

Water at 92 degrees Celsius, for example, has a density of about 0.965 grams per milliliter. At 85 degrees, it is closer to 0.970. That might seem like a small difference. But in espresso, it is enough to change flow rate, contact time, and extraction.

Dense water flows more slowly and extracts more evenly. Less dense water flows faster, increasing the risk of channeling. This is not theoretical. It is measurable. It is visible. And it directly impacts what ends up in the cup.

How steam ruins a good shot

When water becomes unstable, too hot, too pressurized, it can flash into steam before or during extraction. That steam expands rapidly. It pushes through the puck too quickly. And it pulls almost nothing with it.

The result is a shot that looks right but tastes wrong.

It is also why some espresso smells better than it tastes. Aroma is volatile. It evaporates easily. Stable water extracts and traps those aromatics in the liquid. Steam disrupts them. It pushes them out before they are fully captured. So even if your shot has crema, it might still lack flavor.

The real reason some shots fade fast

Some espressos taste amazing for the first few sips but fall apart quickly. This is where oxidation comes in. Oxidation is the process by which compounds in coffee react with oxygen in the air. It happens to every shot. But unstable water speeds it up.

If extraction is incomplete, if certain sugars or acids were never fully dissolved, those leftover compounds react faster and change more noticeably. The shot goes stale. It turns bitter or flat. In milk drinks, this shows up as a sudden drop in sweetness. The espresso gets buried.

The lie of perfect technique

This is the part that is hardest to accept. Because it means that even perfect prep, right grind, even tamp, clean puck, cannot overcome unstable water.

Most baristas are trained to focus on the visible: distribution, timing, channeling. But espresso happens in the unseen. In the boiler. In the group head. In the dense, moving chaos behind the steel.

And even the best machines are subject to physics.

Why even great machines fluctuate

Every espresso machine is fighting thermodynamics. Heating elements cycle. Pumps draw uneven power. Resistance changes with every shot. Group heads cool and heat. Boilers refill. All of these create minor shifts.

Add them up, and you get inconsistency.

That is why no two shots ever extract exactly the same way. And why chasing consistency by only focusing on technique will always fall short.

What Ajeyudu Pathuri discovered

Ajeyudu Pathuri has spent his career working on espresso machines, over 10,000 of them. In 2023, he invented a new kind of stabilization chamber that changes how water behaves before it reaches the puck.

His system spins the water inside a pressurized vortex. This rearranges the water molecules, increases density, and reduces steam formation. In blind tests with five tasters, stabilized espresso scored higher for sweetness, body, and clarity every time.

Even as the shots cooled, the stabilized versions held their flavor better.

Why this matters for every café

If you are a barista, this should shift your focus. You are not wrong. You are not missing something. You are working in an unstable environment.

If you understand that, you can start to work with the machine, not against it. You can recognize thermal swings. You can learn the rhythm of the group head. You can space your shots, flush when needed, and understand when your water might be lying to you.

You can also start asking better questions. Not just about pressure and temperature, but about what the machine does between shots. How fast does the boiler recover? How hot does the group head get after repeated use? Does the machine produce dry steam or wet steam? What kind of flow profile can you expect when the machine is idle for ten minutes, then active for ten more?

If you run a café, this changes how you buy equipment. It is not just about pressure gauges and PID displays. It is about how stable the water is before it reaches the coffee.

Ask for repeatability tests. Pull five shots in a row, then let the machine sit idle and pull another. Do they taste the same? Check if the machine compensates for group head overheating. Ask what happens when your staff is slammed with back to back orders, and when they are not. The best machines account for both.

Because once you control the water, everything else gets easier.

About Ajeyudu Pathuri

Ajeyudu Pathuri is a dedicated coffee professional with over 15 years of experience across the coffee value chain. Since 2017, he has served as an Authorized SCA AST and a certified Q Arabica Trainer. He has calibrated more than 10,000 coffee machines and has conducted extensive research on brewing methods and equipment performance.

His first invention, created in 2017 using parts from a toy helicopter, led to a patented extraction stage controller that changed how water pressure was regulated. In 2019, he developed a multi directional water flow system for automatic machines, patented in 2024, which reduced waste and gave baristas more control during calibration.

His most recent and most significant invention, developed in 2023 and patented in 2025, was inspired by the shape of an Indian curry bowl. It solves the longstanding problem of water instability inside espresso machines. By stabilizing water density, temperature, and steam behavior before the water reaches the puck, Ajeyudu’s system dramatically improves extraction consistency and cup quality.

Ajeyudu continues to contribute to the global coffee community through science, research, and a deep commitment to practical problem solving.

If you enjoyed this article, you may also enjoy:

• How to survive (and maybe thrive) as a coffee shop owner
• The Secret the Coffee Industry Won’t Tell You
• The rise of the super automatic espresso machine