How the moka works: this is how the water rises in the coffee maker

There mocha (whose full name is Moka Express) is one of the objects invented in Italy and today most famous in the world, among the undisputed symbols of Made in Italy. It was launched on the market in 1933 from Alfonso Bialetti and since then, both in design and operation, it has remained practically unchanged. Basically it’s one simple toolemployed for prepare coffee at home, which we all know.

A premise: history and invention of the moka

After spending some years in France as a worker, Alfonso Bialetti he returned to Italy, to Crusinallo, to start the family foundry. In 1919 the Alfonso Bialetti & C. Shell foundryspecialized in the production of semi-finished aluminum productsa material still little used, but which would have a real impact in the following decades boom in numerous sectors.

The most popular story about the birth of the famous coffee makerit is said that, during the 1920s, Alfonso Bialetti imagined the moka while observing washerwomen use the lisciveuse, a tool once used to do laundry. The ancestor of the washing machine, in fact, was made up of a container and a central tube through which the water came to the boil and lyethe “detergent” of the time, came out and was distributed on the clothes.

Starting from this idea, therefore, in 1933 Bialetti created the Moka Expresswhose name was chosen to honor the port city of Mokhain Yemen, from which ships loaded with a fine coffee of arabic quality.


How the moka works

The moka is essentially made up of three parts. Starting from the bottom there is one water heater having a small safety valvethen a container that acts as mechanical filter for coffee powder, funnel-shaped, and a upper jug which is used to collect the drink. The material used is aluminiumalthough for some years it has been possible to find Moka Express models on the market also made in steel. To these three components one is added gasket and then a handle it’s a knob Bakelite.

As far as operation is concerned, it is an overall simple physical process. As the water in the boiler heats upthe pressure increases. When it reaches i 2.3 kPa (we are assuming an environmental temperature of 20 °C), the environment inside the boiler becomes saturated with steam, formed in the top area (which, to be clear, is that area of ​​the boiler that we do not fill with water, stopping as advised by the touch the safety valve). This is a condition called saturated vapor, in which the steam is in equilibrium with the water in the liquid phase. Things change when the pressure inside the boiler exceeds the external atmospheric pressure.

At that point, the steam really exerts a lot of pressure both on the walls of the boiler and on the water below and the latter, therefore, can only begin to rise from the filter spout, the funnel-shaped one. Driven by the steam, it reaches the mechanical filter where the coffee powder is located and extracts it from this caffeine and aromatic substances. Ultimately, the infusion continues to rise in the so-called chimneyuntil it reaches the jug superior.


Curiosities about the moka

The mumble of coffee, that sound that we already know will make our morning better, is the noise produced by steam escapes when the water from the boiler has now almost all risen into the jug.

About the cleaning the moka, however, it is very important to disassemble, wash with running water and dry all the components of the moka after each use, to avoid the formation of mold and limescale. The gasket, safety valve and filter must be checked occasionally.


In this regard, one of the most ignored and important elements of the moka is the safety valve. It is a small opening positioned on the boiler, which is used to make steam escape in case any problems should occur problems. It is also very useful as a measuring cup, marking the level not to be exceeded when filling the boiler with water.

Finally, from the results of a study that investigated the Carbon Footprint (therefore the greenhouse gas emissions produced) in various preparation methods of coffee, it has been proven that the moka is the best option for consumers who are attentive to environmental issues. The production of a cup of coffee, in fact, it produces between 45-57 and 47-59 g CO2e (i.e. equivalent grams of CO2) if the mocha (the two intervals are intended, respectively, for the use of induction plates or gas burners), 74-96 g CO2e when you prefer the use of espresso machines, 72-92 g CO2e if you use pod machines and 57-73 g CO2e for machines in which capsules must be inserted.