主题：Caffe di casa，温馨的家必须有的味道 -- forger

The boiler (marked A in the diagram) is filled with water almost up to the safety release valve and the funnel-shaped metal filter (B) is inserted. Finely-ground coffee is added to the filter as shown below. Then the upper part (C, which has a second metal filter at the bottom) is tightly screwed onto the base. The pot is placed on a suitable heat source, the water is brought to its boiling point, and thereby steam is created in the boiler.

A gasket ensures a tightly closed unit and allows for pressure to safely build up in the lower section, where a safety valve provides a necessary release in case this pressure should get too high (with clean filters, that should not happen).

The steam eventually reaches a high enough pressure to gradually force the surrounding boiling water up the funnel through the coffee powder and into the upper chamber (C), where the coffee is collected. Although the "boiler" on a Moka pot contains steam at elevated temperature and pressure, the water forced up through the grounds is no hotter than that used in other brewing methods - up to 90 °C, depending on the stage of extraction.[8][9]

When the lower chamber is almost empty, bubbles of steam mix with the upstreaming water, producing a characteristic gurgling noise. This "strombolian phase" allows a mixture of superheated steam and water to pass through the coffee, which leads to undesirable results, and therefore brewing should be stopped as soon as this stage is reached