What is the function of a tamper in espresso preparation?

The primary function of a tamper in espresso preparation is to compress the coffee grounds evenly in the portafilter. When preparing espresso, it's essential to have a consistent and uniform coffee bed, as this affects the extraction process. By pressing down with a tamper, you create a solid puck of coffee, which allows water to flow evenly through the grounds during brewing. This compression helps prevent channeling, where water finds easier paths through the coffee, which can lead to uneven extraction and ultimately result in a poor flavor in the final espresso shot.

The tamper ensures that there is a good amount of density and resistance as hot water passes through the grounds, allowing for the optimal extraction of flavors and oils. This is crucial for achieving the rich, bold taste that espresso is known for. Ensuring even compression is vital because unevenly tamped coffee can lead to bitter or under-extracted shots, affecting overall quality.