Should Coffee Grounds Be Tamped in a Moka Pot? What's the Ideal Grind Size for Moka Pot Coffee?

When brewing coffee with a moka pot, many people are unsure what grind size of coffee powder is appropriate. They also don't know how to fill the coffee powder properly - should they tamp it or not? If you have these questions, you'll find the answers in the following text.

What grind size does moka pot coffee powder need?

The coffee particle size required for a moka pot should be around 0.3-0.55mm. This means it shouldn't feel rough like sand particles, but it's also not as fine as the powder used for espresso machines, which feels like flour. You can test this in two ways: first, purchase a particle size gauge or moka-specific powder as a reference; second, through continuous trial and error. Usually, it won't take many attempts - after 3-5 tests, you'll generally get the hang of it. If the grind is too coarse, the coffee liquid will spray out quickly, possibly like a fountain. If it's too fine, you'll hear the bubbling sound of boiling water, but the coffee liquid hasn't come up yet - this means it's too fine, and you should quickly turn off the heat. Remember to take safety precautions when conducting such tests.

Do you need to tamp the coffee powder in a moka pot?

FrontStreet Coffee, through numerous experiments, believes this is unnecessary because if you can't master the tamping pressure, you might compact the coffee powder too tightly, preventing water from penetrating the coffee puck, which is very dangerous. Of course, some friends worry that not tamping might cause "channeling," where coffee liquid sprays out forcefully.

FrontStreet Coffee recommends this filling method, which can effectively prevent this phenomenon and produce very rich coffee crema.

Use your right hand to hold the filter basket, then fill it with coffee powder without compressing it, keeping it in a fluffy state and forming a small mound in the middle. You don't need to level it because the top pot's filter screen is also convex upward. Then simply press the top pot on vertically and tighten it. Be sure to clean any coffee residue from the threads. (Note: The coffee powder must fill all the gaps around the edges.) This way, the extracted coffee grounds will be firm and won't fall apart. Moreover, the extracted coffee crema will be very rich.

No coffee liquid comes out after brewing for a long time

There are two main reasons for no liquid output. First, the coffee powder is packed too tightly. Second, the coffee powder is ground too fine, leaving no space between particles for water to pass through. Both situations cause the internal pressure in the water chamber to rise rapidly, potentially damaging the moka pot. Therefore, if you've been brewing for a long time, the water is boiling, but no coffee liquid comes out, immediately turn off the heat and remove the pot. You can only replace the powder and start over. (You can usually smell a burning smell at this point.)

Coffee liquid sprays out forcefully

Coffee liquid splattering is the most common extraction problem many people encounter when using moka pots, and it's also a situation with higher risk. If you've experienced this splattering phenomenon, it indicates that something inside the pot is blocked, or the heat is too high, causing excessive and rapid liquid output. Pay attention to the amount of water added to the lower chamber - it should not exceed the standard marking line,控制在泄压阀线以下0.5cm处. This valve prevents explosions caused by excessive pressure due to certain factors (such as coffee powder being too fine). If water covers this valve, it might lose its pressure relief function, creating a risk of explosion.

The moka pot's grind size is generally slightly coarser than espresso powder but much finer than pour-over coffee. If the grind is too coarse, the contact area between water and coffee powder is smaller, which not only leads to insufficient extraction and weak flavor but also causes the liquid to spray out due to too little resistance, creating a danger of splattering burns. FrontStreet Coffee recommends a grind size of EK-43s #3-3.5 setting, which feels finer than fine granulated sugar.

Coffee has no crema

The amount of crema produced in coffee is directly related to the roast level and freshness of the coffee beans. The darker the roast and the fresher the beans, the richer the crema layer will be produced under high temperature and pressure conditions.

Since the moka pot uses pressure extraction, if you use light-roasted coffee, the beans are harder in texture and typically require a finer grind to increase extraction rate. However, fine grinding under high temperature and pressure tends to make coffee sour and harsh, and it's also difficult to present the aroma of crema. Therefore, FrontStreet Coffee recommends using medium to dark roast coffee beans, which not only ensures good flavor but also makes it easier to extract crema.

Why is the coffee so bitter and burnt-tasting?

Unlike professional espresso machines, moka pots don't have an even distribution screen (filter basket); they only have a small hollow column for liquid output. Whenever the powder is too fine or there's too much of it, it becomes difficult for liquid to exit, so coffee can only find looser areas around the filter basket to flow out. In this situation, usually the center of the coffee grounds in the filter basket is dry, while the surrounding area continuously receives the "baptism" of high-temperature hot water, constantly extracting. This causes the coffee to be both over-extracted and under-extracted simultaneously, resulting in a bitter, burnt taste that's hard to swallow.

For professional coffee knowledge exchange and more coffee bean information, please follow Coffee Workshop (WeChat official account: cafe_style).

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