Tamping espresso: why pressure is not the point

Tamping espresso: why pressure is not the point

You hear it on YouTube all the time. You see it in every bar. The tamper comes down, a dull click, then a second push. With it, the eternal refrain: thirty pounds. Thirteen kilos. As if on a scale. Anyone who does not tamp like that is tamping wrong.

That is half true and mostly misleading. What actually matters when tamping is not the number on a pressure gauge. It is a level surface, even distribution and repeatability. If those three things are right, you can tamp with five kilos or with fifteen kilos. The espresso will still taste good.

What tamping actually does

You put ground coffee into the portafilter. That is thousands of tiny pieces with air between them. Hot water comes in at around nine bar of pressure and looks for the path of least resistance. If the distribution in the puck is uneven, the water breaks through at one spot and ignores the rest. That is called channeling. The result: a sour, thin, dull espresso. Tamping compacts the grounds into one closed layer. Only then does the water have to push through everything and not only through the weak spot.

The number everyone names

Thirty pounds of pressure, around thirteen kilos, was the mantra for years. A Specialty Coffee Association survey showed that most baristas tamp between twenty and thirty pounds. But more recent research is clear: the extraction barely changes whether you tamp with five pounds or with forty. As long as the puck is evenly compressed, almost the same thing comes out at the bottom.

That does not mean pressure is irrelevant. You need enough pressure so no air gap remains between tamper and grounds. Above that point, it is mostly theatre. Your shoulders get tired, the espresso does not get better.

What really counts: level, even, repeatable

The most important step happens before the tamp. How do the grounds sit in the portafilter? Clumpy? One side higher than the other? If yes, you can tamp however you want, the water still finds the thinnest point.

Distribution. Before you tamp, the grounds should sit evenly in the basket. One method is the Weiss Distribution Technique, WDT for short. With fine needles, often 0.3 millimetres, you stir through the freshly ground coffee and break up clumps. John Weiss invented this in the early 2000s. Today it is standard in every decent specialty bar. The result: no channeling, more even shots, less frustration when dialling in the grinder.

Level. Tamp straight. If you press the tamper at an angle, one side becomes denser than the other and the water takes the looser side. Look at the rim. Does the tamper touch the inner edge of the basket all the way around? Then it is right.

Repeatable. What you do today, you should be able to do tomorrow. That is why calibrated tampers are popular: they set a fixed pressure point and you only have to press level. Grinding becomes the variable, tamping does not.

The steps in the right order

Grind fresh into the portafilter. Tap the sides gently so the coffee settles. Distribute with a WDT tool or your finger, so clumps are gone and the surface looks even. Place the tamper on top, hold the portafilter straight on a flat surface. Press straight down. That is all you need. The whole sequence takes less than ten seconds.

The SCA numbers worth knowing

For tamping to make sense, a few other things have to be in place. The Specialty Coffee Association gives this range: for a double espresso, 14 to 20 grams of coffee, 25 to 30 seconds of extraction, a ratio of grounds to final espresso between 1 to 1.5 and 1 to 2.5. Extraction yield should ideally sit between 18 and 22 percent. When your espresso falls outside those ranges, it is rarely the tamping pressure. It is usually the grind, the bean or the machine temperature.

What this means in practice

Stop worrying about the number on a pressure gauge. Focus on the grounds sitting flat and even in the basket. Invest first in a decent grinder and a WDT tool before you spend on the most expensive tamper. Pull a few shots with a bottomless portafilter and watch the crema. Does it drip evenly from all points? Then you are good. Splashing from one side or a blonde stream in the middle? That is uneven distribution, not too little pressure.

And yes, a great bean still needs all of this to show what it can do. If you are looking for espresso beans from the Swiss specialty scene, browse Röstpost. Different profiles, different roasters, something new to try every week. Then you already have the best you need in the portafilter, and the rest is practice.