Champion Italian barista Alessandro Galtieri speaks with Tanya Nanetti about the importance of espresso tamping and why only the best tamping technique will result in a satisfying brew.

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Numerous factors go into preparing a good cup of espresso, from a precise grinder to the perfect water temperature. However, one aspect that is often overlooked and underrated is the value of a good, consistent tamping technique.

According to Alessandro Galtieri, the 2018 and 2019 Italian Brewers Cup Champion, tamping is one of the fundamental stages of “espresso puck” preparation. (The puck is the compressed disc of coffee grounds inside the portafilter.)

In its most basic form, it involves tightly compressing coffee grounds using a tamper – a flat-bottomed tool that allows baristas to apply pressure and create an even distribution of coffee across the portafilter.

But while it may seem simple enough, tamping can very easily go wrong. Tamping too hard or too light, or in a way that creates an uneven bed can quickly ruin what could otherwise be a delicious cup of espresso.

These days, many use automatic tampers, such as the Slingshot, which can be programmed to tamp at precise pressures and avoid repetitive strain injury in baristas. However, it is still important for baristas to develop an understanding of what constitutes a good tamping technique.

The problem of channelling

When the predetermined dose of coffee is poured into the portafilter, there are typically small gaps of air between the grounds. Some of these voids may be a little wider than others, creating variations in resistance.

Resistance is crucial to espresso preparation. Typically, steam pressure generated by an espresso machine’s boiler forces hot water through this coffee puck, creating the rich, syrupy, crema-laden espresso that the world has come to love.

However, uneven pressure equates to uneven coffee extraction, leading to a drink that’s either under or over-extracted. Water follows the path of least resistance, meaning that uneven gaps of air are likely to give rise to a problem known as channelling.

“Water will dig a small channel in that point, through which more and more water will pass with increasing speed, while it will continue to flow more slowly and poorly in all other points,” Alessandro explains. “An irregular extraction leads to all possible defects in the cup: sourness, bitterness, poor quality, and astringency.”

An untamped bed of coffee is soft, meaning the first drops of water that hit it will form holes, which inevitably will develop into channels. By tamping properly, however, Alessandro says it reduces the chance of this happening.

“The gaps are minimised and the surface of the cake becomes more solid,” he says, “therefore, reducing the likelihood of channelling.”

It’s also crucial to note that if the puck isn’t level, the lower part of the puck could overflow with water. It’s for that reason that some tampers feature ridges on their bottoms, which, when rotated, levels the coffee grounds.

Finessing the technique

“The first thing I would like to recommend to a home barista is to focus on the result rather than on the technique,” Alessandro says. “Many people who approach tamping are so busy performing the procedure that they end up neglecting the result of their effort. Simply put, the cake has to be uniform.”

For him, the first step to perfect tamping is to find the right equipment for the job. He explains that even though the role of the tamper may seem banal, good tampers aren’t always easy to find.

“The function of the tamper, as we have said, is to create a compact and uniform surface. Therefore, it must first of all have a diameter that matches that of the filter, otherwise only a part of the coffee will be pressed.”

Many tampers, however, have bases that don’t precisely match standard filter baskets. The result is a large amount of non-compacted coffee around the edge of the basket, which is more susceptible to channelling.

Baristas should also choose a tamper with a perfectly flat lower edge, as a rounded edge will also result in uneven pressure distribution around the edges of the basket.

In terms of technique, Alessandro says that it is “all about consistency and care”. Although plenty of pressure is required, pressing too hard often reduces the precision and repeatability of the action and subjects the barista’s joints to unnecessary strain and damage.

“When the tamper finishes its downward motion, it means that the gaps between the granules have been filled,” he adds. “A pressure slightly above this threshold is already sufficient to seal the panel at the edges of the filter.”

For high-volume coffee shops, automatic tampers such as the Slingshot Kilo, are perhaps a better option. Not only do they take less than a second to perform a highly precise tamp, they can also save time and effort, while being better for the long-term well-being of baristas.

Automated machines like these make life easier for professional baristas and prosumers alike, but it’s still up to the person behind the machine to undertake careful grind distribution.

Ultimately, whether opting for the manual or automated approach, the result of good tamping will be the same: delicious espresso with a thick crema, ready for sipping.