Mechanics of coffee percolation

Aromatic compounds and other flavour compounds are extracted from coffee grains by the Moka using a process known as percolation. The verb to percolate is defined as: to cause a solvent (i.e.: water) to pass through a permeable substance (i.e.: coffee) especially for extracting a soluble constituent. In order to percolate or brew the coffee the percolator is placed on a stove element and heated until pressure in the water compartment increases causing the water to rise through a funnel, through the coffee grains, through a filter and, finally, into the top compartment. According to the Bialetti corporate lore the mechanical design for the Moka was inspired by the primitive washing-machines used by housewives: linens were boiled in tubes built around a central conduit that drew the boiling soapy water up through it and redistributed it across the linens through a radial opening.

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