You asked under our moka film. Here's why, measured: the hot base keeps pushing, and the last of the water boils through your coffee as steam.

1. Cold water ready before you light the hob
2. Dark roast? Fill the base only three quarters
3. Heat off as soon as the first coffee shows
4. Too fast? Lift it off. Too slow? Back on
5. Stop at the first hiss
6. Base into cold water for 10 seconds
7. Pour it out right away: two-thirds of the water out is plenty

Researchers at the University of Trieste and illycaffè measured a 3-cup moka: the water in the base was about 70 °C when the coffee started and about 120 °C when the gurgle began, the last fifth of the water boiling through the coffee (Navarini et al., 2009). Bialetti's own instructions don't ask for the cold water: they say take it off the heat at the end and let it cool before opening. We follow James Hoffmann and Complete Home Barista, who stop at the first sputter and cool the base; the numbers are why. Cold water is a stop button, not a flavour of its own: the film shows what it stops, not a taste score. The pot is our own drawing of a generic one.

Which brewer should we do next?

Sources: Navarini, Nobile, Pinto, Scheri and Suggi-Liverani, Applied Thermal Engineering 29 (2009); James Hoffmann, The Ultimate Moka Pot Technique; Complete Home Barista; Bialetti instructions; W. D. King, American Journal of Physics 76 (2008).
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