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.
Background & Context
Percolation par extraction (percolation extraction in English) is the French terminology for the family of brewing methods in which water passes through and beyond coffee grounds, extracting compounds progressively as it flows. The phrase distinguishes these methods from immersion (par immersion) where grounds and water remain in contact throughout steeping. In French specialty coffee vocabulary, percolation encompasses: filtre (V60, Chemex, Kalita, drip machine), espresso (by pressure), and moka pot (by steam pressure). Each percolation method varies the pressure and flow rate: gravity filtration operates at 1 bar atmospheric pressure; moka pot at approximately 1.5 bar steam pressure; espresso at 7–9 bar pump pressure. The increasing pressure correlates with faster extraction, higher TDS concentration, and greater emulsification of coffee oils — which is why espresso has far higher body and concentration than drip coffee at identical dose.
Practical Use
For French-speaking baristas and coffee educators, the percolation/immersion distinction provides a precise vocabulary for explaining how brewing method shapes cup profile. A student who understands that percolation extracts more volatile aromatics (because fresh water contacts grounds continuously) but produces less body (because fewer colloidal particles are carried through the filter) can predict flavour differences between methods without tasting — and can adjust recipes intelligently when switching from one percolation method to another. The transition from V60 to Chemex, for example, is a percolation-to-percolation switch — both use gravity flow, but Chemex's thicker paper filter removes more colloidal particles, producing greater clarity and less body at equivalent extraction yield.
Related Terms
Related terms: Percolation extraction, Percolation méthode, Immersion par extraction, V60, Espresso extraction.