Moka pots are used over a source of heat, typically a flame or electric range. Stainless steel pots, but not aluminium, can be used with
induction cooking. There are three major components in a typical moka pot: The
lower chamber or
lower vessel, also known as the
boiler, which is fitted with a
safety valve to prevent over-pressurization The
filter funnel or
basket, which compresses an annular rubber
gasket when the moka pot is assembled and seals against an upper
filter disc The
upper chamber or
upper vessel, also known as the
collector, which is where the coffee is deposited during the brewing process The moka pot is assembled first by inserting the filter funnel into the lower chamber, then threading the upper chamber onto the lower chamber, which compresses the rubber gasket against the lip of the filter funnel to seal the lower chamber. Generally, the upper filter disc is retained on the bottom of the upper chamber by the rubber gasket, which acts as a flexible internal
circlip; this filter disc prevents coffee grounds from moving up the spout of the upper chamber.
Preparation The boiler (marked A in the diagram) is filled with water to an etched line (or slightly below the safety release valve). While at-home makers generally do not preheat the water used, it can expedite the brewing process in commercial settings. The metal filter
funnel (B) is inserted. Finely ground coffee is added to the filter. How tightly the coffee is packed impacts how quickly the coffee extracts and the strength of the brew. The collector (C) is then attached and the pot is heated. File:Coffee f3327912.jpg|Funnel with ground coffee File:Moka brewing.jpg|Mid-brew, showing brewed coffee in the process of being transported through the spout File:Moka crema1.JPG|Layer of
crema developing
Brewing video of a moka pot in use The heating of the boiler (A) leads to a gradual increase of the pressure due to both the expansion of the enclosed air and the raised
vapor pressure of the increasingly heated water. When pressure becomes high enough to force the water up the funnel through the coffee grinds, brewed coffee rises through the vertical spout and pours into the upper chamber (C). When the lower chamber is almost empty, bubbles of steam mix with the upstreaming water, producing a characteristic gurgling noise—a signal that brewing should be stopped. Navarini et al. call this the "
strombolian" phase of brewing, which allows a mixture of highly heated steam and water to pass through the coffee, which leads to rapid overextraction and introduction of undesirable flavors.
Moka coffee characteristics Brewed coffee flavor, including that of a moka pot depends greatly on bean variety, roast level, fineness of grind, water profile, and the level of heat used. Moka pots are sometimes referred to as stove-top espresso makers. However, a typical moka coffee is extracted at relatively low pressures of , Typically, the moka pot uses a ratio of coffee to water, by mass, of approximately 1:10, resulting in a brew with approximately 3–4% dissolved solids. In comparison, espresso is "stronger" with 9–10% dissolved solids, and drip-brewed coffee is "weaker" with approximately 2% dissolved solids. The caffeine content of moka coffee has been measured at 128–539.9 mg/100mL. ==Maintenance==