Percolation (extraction method)

In percolation extraction, hot water flows through a bed of ground coffee and exits through a filter, carrying extracted solids and dissolved compounds. Unlike immersion, fresh water continuously contacts the grounds, enabling extraction yields above the immersion equilibrium plateau (~22% EY). Espresso (9 bar, 30 ml water/18 g coffee) and pour-over (V60, Chemex, batch brew) are percolation methods. Flow rate and grind size are the primary variables controlling extraction speed and yield.