A French press, also known as a cafetière, сafetière à piston, Cafeteria, press pot, COFFEE PRESS
, or coffee plunger, is a coffee brewing device patented by Italian designer Attilio Calimani in 1929.
A French press works best with coffee of a coarser grind than does a drip brew coffee filter, about the consistency of kosher salt. Finer grounds, when immersed in water, have lower permeability, requiring an excessive amount of force to be applied by hand to lower the plunger and are more likely to seep through or around the perimeter of the press filter and into the coffee. Additionally, finer grounds will tend to over-extract and cause the coffee to taste bitter. Coffee is brewed by placing the ground coffee in the empty beaker and adding hot-between 93–96 °C (199–205 °F)-water, in proportions of about 30 g (1.1 oz) of coffee grounds to 500 ml (17 US fl oz) of water, more or less to taste. The brewing time is about two to four minutes. The plunger is pressed to separate the grounds and hold them at the bottom of the beaker. The mesh piston normally does not compress the coffee grounds, as most designs leave a generous space-about 30 mm (1.2 in)-below the piston in its lowest position. If the brewed coffee is allowed to remain in the beaker with the used grounds, the coffee may become astringent and bitter, though this is an effect that some users of the French press consider desirable. It is believed that the optimum time for brewing the coffee is around four minutes, and some consider the coffee spoiled after about 20 minutes. Other approaches, such as cold-brewing, require several hours of contact between the water and the grounds to achieve the desired extraction.