How do they work?
The Moka pot has 3 parts that are screwed together tightly:
- a chamber at the bottom (B): you put cold water in here
- a chamber at the top (T): the brewed coffee gets collected here
- a funnel shaped filter in the middle (F): you fill it with ground coffee
When the water in the bottom is heated up it generates steam. This
steam increases the pressure in the bottom chamber and this pressure
starts to push the water up through the filter and into the top
When the rising water reaches the ground coffee, the coffee soaks some of
the water and expands - so it effectively tamps itself. The tamped
coffee puts up a resistance that the rising water has to overcome
- so as a result higher pressure is needed to push the water up (that's
why we call this an espresso maker rather than a coffee maker).
When the last bit of water is going up to the top chamber the Moka pot makes
a characteristic gurgling sound and the brewed coffee at the top is
ready for drinking.
Types of Stovetop Espresso Pots
Stove Top Espresso Maker: Aluminum or Stainless Steel?
Stainless Steel Stovetop Espresso Maker
Stove Top Espresso Coffee Maker: Tips