In Germany, we call the procedure “tampen”. Which can easily be confused with a piece of rope, which is called “Tampen” in German as well. But as we learned, the word derives from the English language and means something completely different. The “tamper” is used to press the ground coffee into the portafilter, when making an espresso. According to a widespread misbelief this is done to slow down the throughput speed of the water. But tamping is more about compacting the ground coffee evenly and to create an even surface. Why?
Water always takes the path of least resistance. A flat and even surface allows the water to evenly flow through the ground coffee. If the grounds are uneven, so-called channels will be formed which leads to an over extraction of the coffee, meaning that more bitter substances are extracted. In some areas it will be under-extracted, which keeps the aromas from developing. You can imagine that the result will be a not so tasty espresso.
So please, do not forget the tamping. Besides, a tamper is also a pretty kitchen accessory.
By the way, when using the stovetop coffee maker, also known as Bialetti or Caffettiera, never tamp the coffee into the filter. The result would taste bitter and awful.
Are you interested in more shop talk on espresso, portafilter machines, and the like? Then check out the article “Portafilter – (not) a male preserve?”.