The problem called "channelling" or when espresso fails


When setting up a recipe for your espresso, you're trying to find the perfect intersection of several factors. You need thehot water to flow through the ground coffee, using a given pressure, at exactly the right speed to extract all the positive ingredients in the coffee. This is achieved byadjusting the properties of the water and coffee appropriately . As far as the water is concerned, you can adjust its quantity, temperature and, last but not least, its composition by using filtration. With coffee, you can also change the coffee weight for each individual serving and then the fineness of the grind, which has a major impact on the final espresso.


The moment you press the brew button on the coffee machine, hot water from the boiler of the machine makes its way to the lever where the ground coffee awaits. Theground coffee in the lever prevents the water from simply flowing into the cup, and depending on how much the coffee obstructs the water, the substances in the coffee will be extracted into the water.

For example, you calculate a recipe where you use 18 grams of properly finely ground coffee and you are delighted that in 28 seconds 54 grams of perfectly balanced espresso (or more accurately doppio, with espresso you would have to let this amount of coffee flow into not one, but two cups, i.e. two espressos) into your cup. Even if this setup really does mean that the coffee in the lever set up in this way will present the most perfect barrier to water in the espresso process, you may encounter a failed result.


Water always seeks thepath of least resistance and once it finds it, it creates an easy flow there - a channel. When a channel forms, it means that thecoffee around it will be over-extracted as it will be touching the water for a long time. In contrast ,other coffee particles will not be extracted at all because the coffee will avoid them through the channel. This unbalanced extraction results in an unbalanced espresso.

The best way to notice the channeling is to prepare the coffee using the "naked lever". This lever does not have a bottom, so we can see right away with our own eyes whether the coffee is flowing out of the strainer evenly and in the middle, or flowing out unevenly.


There are several signs that the water has found its own fast path in the coffee:

  1. A quick start: usually nothing visible happens for the first 5-8 seconds after the water is allowed into the lever. Only then do the first drops of espresso arrive in the cup. If the coffee has the opportunity to form a channel and bypass the amount of coffee, the liquid appears in the cup earlier.
  2. Short extractiontime: by having a path through the coffee, the water manages to flow into the cup in less time.
  3. Larger espresso: because the water passes through the coffee faster, the resulting espresso has a larger volume after the exact extraction time has elapsed.
  4. Weak crema: fast flow through the coffee will cause insufficient extraction and therefore a thin and light crema.
  5. Holes in the puck: another visible sign that you have a channelling problem are telltale traces in the coffee puck. The coffee bud, that is, the bud-shaped coffee that you tap out of the lever after use, has signs of these water channels on it
  6. The resulting taste: the most important argument for improving espresso technique. Channeling means over-extraction and the taste of such coffee is weak and bitter. At the same time, coffee that has been touched only minimally by water before it passes through the channel is as acidic as unripe fruit.


Solve the channelling problem by removing the causes that allowed the water to form channels in the coffee. First, make sure that you are not creating the conditions for channelling yourself with your bad practices.

Cart cleanliness

We would amend the well-known adage to "unclean basket - half way to canalisation" for our purposes at the moment. Therefore, use a clean and dry lever. He, the kind of cloth that the barista has pinned to his apron, is a functional addition to the professional barista's equipment. With an unwiped lever, into which you pour a new batch of coffee, you create the foundation for the water to channel.

Little coffee

The basket in your lever determines how much coffee can hold. Depending on what basket you have, you weigh the coffee. So, for example, if you have a basket for 17 grams of coffee, create an espresso recipe that accounts for that amount of coffee in the lever. Do not underestimate this volume (+/- 1 gram). Overfilling will put too much strain on the water getting into the cup and therefore overextracted coffee. A smaller amount of coffee will give the water more room in the basket and make it easier to create channels.

Also, when inserting the lever with an overfilled basket into the head of the coffee maker, the pile of coffee may cause the seal to not seal to the lever. Water may then leak from the lever. At the same time, this will damage the seal itself.

Grinding too finely

The disadvantage of grinding too finely is lumping. Coffee ground too finely tends to clump. Even after pressing with a tamper, this ability of too fine coffee particles to stick together will persist and make it easier for water to get around them. The aid to break up these lumps and properly distribute the coffee is called a distributor. More and more baristas are using his help to settle the coffee in the lever.

The best way to notice the channeling is when making coffee using the "naked lever". This lever has no bottom, so we can see for ourselves whether the coffee flows evenly and centrally from the strainer, or whether it flows unevenly.

Uneven tamping

When tamping, it is important to press the coffee evenly. That is, so thatone side of the tamped coffee is not lower than the other. This is because the water will naturally flow to the side with the lower resistance, where it will flow into the cup, and the coffee will remain essentially untouched by the water on the higher side. Another consequence of uneven pacing is that (when using the lever for two espressos) there will be more coffee in one cup and less in the other.

Do not tap after tamping

You make sure the lever, the weight and the grind are clean and then tamp the coffee nice and evenly. Then, perhaps by mistake, you tap it on the table top, miss the lever when putting it in the machine, or think to tap the lever again to tidy up the coffee from the edges and make the tamped coffee look nice in the lever. The result of all these scenarios is that youbreak the original proper tamping of the coffee, which in theedges loosens from the sides of the basket. This then re-creates a path for the water to circulate around the coffee.


Have you avoided the mistakes that promote channelling and the problem hasn't stopped? Perhaps you need to investigate the technical possibilities and the correctness of the aids used.

The size of the tamper

The right tamper can make the job of making coffee easier. Make sure you use a tamper with the correct size for your basket. If the tamper does not fit the sides of the basket, it will not compress the coffee in these areas around the edges. If you make coffee really often, when looking for a new tamper, consider theautomatic tamping option with thePuqpress. By investing in this automatic helper, you'll ensure the same precise tamping every time you make an espresso. Consistently tamped coffee will make your preparation much easier.

Consistent grinder

We consider proper grinding to be the foundation of proper extraction and therefore good coffee. A reliable grinder should be an essential piece of equipment in the coffee corner of your kitchen. If you were looking forward to saving money on a cheap grinder, you will unfortunately be disappointed. Only a quality grinder is capable of consistent grinding. If you use coffee from a cheap grinder that grinds inconsistently, i.e. with large variations between the size of the ground particles, you will not achieve the right extraction in your espresso. The large coffee particles in the lever help to form channels between them, which is what causes your coffee to be unevenly extracted.

Remember to take care of your grinder and clean it regularly. If you have an older, frequently used grinder, thegrinding stoneswill no longer be sharp enough. Have it serviced or replace the stones yourself.