A moka pot a.k.a. espresso maker is based on steam pressure distillation . It consists of three chambers as you can see in the picture. Below I will briefly describe the function of the pot and how to use it effectively.
The bottom chamber (A) is filled with water. Please make sure that the water level is lower than the safety valve as it acts as a pressure release. Blocking it by too much water will result in increased pressure which can cause your moka pot to explode.
The middle chamber contains a filter basket with a long tube (the filter funnel) that reaches into the water. By bringing the water to a boil, the steam will rise and go through this tube to transport the coffee or espresso aromas to the upper chamber (C). On its way up, it will pass the coffee grounds, go through another filter and a rubber gasket which are located above the filter funnel and rise higher through the column that releases the finished brew into the top chamber.
Of course, there are many different ways to use a moka pot. Therefore, I will briefly describe the different variations so you can choose for yourself which one you like best.
1. Filling the moka pot with water. You can now decide whether you would like to fill the bottom chamber with hot or cold water. Some say by using hot water, the steam is exposed to the coffee grounds for only a short time and thus the aromas cannot become bitter during the brewing process since the metal becomes very hot, too, and could lead to scorching of the finished brew. Cold water needs to be brought to a boil and therefore prolongs the brewing.
2. Fill the filter basket with freshly ground coffee or espresso powder - do not use a finished powder as it will have a tremendous impact on the quality of the finished brew. You will taste the difference! Moreover, it is very important to use a coarser grind than you would normally use for a regular espresso or coffee machine. The coffee/espresso powder should not be too fine as it would block the holes in the filter and the steam could not properly rise through the grounds. Fill the basket with the grounds, but do not tamp as it might block the water flow. Simply distribute the grounds evenly in the basket.
3. Insert the filter basket into the bottom chamber and screw the moka pot together tightly as you want to avoid steam escaping during the brewing process or coffee will spew out. This can be very painful!!! You should also wipe off any grounds from the threads and gaskets before assembling the pot. Better be safe than sorry!
4. Now place the moka pot on a stove and bring everything to a boil using low to medium heat. Too high temperatures can cause the steam to rise too quickly which would prevent it from collecting the fine aromas from the grounds. Some people leave the lid open during brewing as they are convinced that the condensing water might dilute the coffee/espresso. We recommend trying both methods to see which one works best for you to get good results. As mentioned before, using moka pots involves a lot of experimenting, but that's what makes it so interesting!
5. You know your coffee/espresso is ready when you hear a "gurgle" coming from the bottom chamber. That means the water is exhausted and your coffee is ready! Pour it and enjoy! ;-)
Cleaning: Moka pots should never be cleaned with detergents as it destroys the layer of coffee oil on the inside of the top chamber. These oils enhance the flavor of your brew and avoid direct contact with the metal surface which can leave a metallic aftertaste in your coffee. Therefore, the oils should not be removed. It's enough to clean the pot with hot water and a soft brush/sponge.
When using a moka pot for the first time is it also advised to brew coffee with old grounds, let's say, three to four times in order to test the function and to avoid a metallic taste as the insulating layer of oil has to be created first. So instead of throwing your old grounds away, use them to get the pot going!
As for me, I hope you will have much fun with your moka pot and create your own unique coffee/espresso recipes with it. It's a fast and cheap way to brew your favorite beverage and due to the size you can also take it with you to work using an electric hotplate. It saves time and can even inspire you to create your own recipes, eg. using cinnamon or chili along with the coffee grounds or other spices. Try and see what happens! ;-)