The field notes
A little pot.
An upward journey.
A moka pot is a stovetop coffee maker with a water chamber below, a funnel holding ground coffee in the middle, and a collector above. Its upward path is the interesting part: pressure in the lower chamber moves liquid water through the coffee. Our cutaway follows that journey inside one conventional pot.
Start with water, air and coffee
The funnel connects the chambers
The funnel’s narrow stem reaches into the lower water chamber. Its wider basket holds the ground coffee above the starting water level. The pot is assembled before heating. The transparent walls in our film are an illustration, not a step that asks you to open a hot pot.
Follow the liquid upward
Pressure acts on the water below
As pressure rises in the gas space, liquid water moves up the submerged stem and through the coffee bed. Passing through the grounds extracts coffee into the water. The film changes the liquid’s color as it crosses the bed to make this path visible.
Collect the brewed coffee
Through the chimney, into the upper chamber
The brewed coffee travels up the chimney and flows into the upper collector. This lesson shows the regular liquid-flow part of brewing. It stops before the late stage when gas can break through and the pot begins to sputter.
Brew Basics · Part 1 of 3. Before heating, keep the water below the safety valve and fill the coffee basket without tamping. Follow your model’s instructions for the complete preparation and compatible heat source. Next in this series: the AeroPress.
Explore another brewer: What is French press coffee? ↗
Follow a different water path: What is pour-over coffee? ↗
Read the narration Full video transcript
How does coffee climb inside this little pot?
This is a moka pot. Its bottom chamber holds water, with air above it.
The funnel's stem dips into that water, while its basket holds the ground coffee.
As the sealed pot heats, the trapped air warms and more water evaporates. Together, the air and water vapor raise the pressure above the water.
That pressure pushes liquid water up the stem and through the grounds, picking up flavor.
The brewed coffee then rises through the chimney into the top chamber.
Brewing can begin before the water boils.
Keep the water below the safety valve, and fill the coffee basket without tamping.
That's the little pot's secret: pressure moves the water. Follow for our next lesson: the AeroPress.
Moka pot · Sources
- Bialetti Africa · How the Moka worksThe manufacturer’s regional explanation identifies the lower chamber, funnel and upper collector, and the water path through the pot.
- Bialetti · How to use the Moka Express?Manufacturer operating instructions place the starting water below the safety valve, preserve headspace and call for loose grounds without pressing.
- Navarini and colleagues · Moka extraction study (2009)Applied Thermal Engineering29,998–1004. The experimental paper examines the contributions of air and water vapor to pressure and the start of liquid extraction before boiling.
- Read the research paper · Full-text PDFA publicly accessible copy of the same primary study, including the lower-chamber pressure measurements and regular-extraction discussion.
The cutaway, particle symbols and flow are simplified original illustrations, not a product diagram to scale. The film explains early and regular extraction, not a complete brewing recipe or the late sputtering phase. It makes no espresso-equivalence, caffeine or health claims. Sources checked November 4, 2026.
A little more familiar with your cup.
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