What is the act of tamping espresso grounds meant to achieve?

Tamping espresso grounds is a crucial step in the preparation of espresso that aims to create a level and compact surface for even extraction. When the grounds are tamped down, the barista applies uniform pressure to ensure that the coffee particles are densely packed. This density is essential because it allows water to flow through the coffee grounds uniformly during the brewing process. An even extraction is vital for producing a balanced flavor profile, allowing for the desired oils and solubles to be efficiently extracted.

Proper tamping helps prevent channeling, where water finds a path of least resistance and bypasses some grounds. This can lead to over-extraction of some areas and under-extraction of others, resulting in an uneven and unsatisfactory shot of espresso. Therefore, a well-executed tamp creates the necessary conditions for a rich, consistent, and high-quality espresso shot.