Wrong Channels: How to Prevent Channeling in Espresso

Whenever Astro-TV mentions channeling, it’s viewed positively without exception; after all—so the claim goes—it’s a way to make contact with spirits, such as deceased relatives. In fact, “channeling” means “receiving something through a channel,” and the principle is the same whether you’re contacting your great-grandmother or making an espresso. Channeling while making espresso is negative, but so can contact with your great-grandmother be.

With espresso channeling, the water flows through a channel in the coffee grounds—the ground beans in the portafilter—during preparation. As a result, the espresso is not extracted evenly. Ideally, of course, the water should flow evenly through the coffee grounds—the so-called “cake”—rather than through a channel that bypasses most of it.

The principle is a simple one based on physics: Water takes the path of least resistance, so it forms a channel where the “cake” is more permeable than in other areas. The solution to this problem is to prepare the coffee grounds in the portafilter before extraction so that they are evenly distributed.

Step 1: Tap

You can prevent channeling even while grinding. When the ground beans land in your portafilter, pause once in a while. Pull the portafilter away and tap it gently so that the grounds spread out evenly in the portafilter and don’t form a mound. Then you can finish grinding the rest. Before moving on to the next step, tap the portafilter lightly again so that the last of the grounds are distributed. But listen to our barista Micki from our café in Wedding: “Don’t tap too hard, or the grounds will settle too much and slide too far down.”

Step 2: Leveling

The grounds are now evenly distributed, but—as you can see—they’re so loose that dozens, if not hundreds, of larger and smaller channels have formed, which can really ruin your espresso. The grounds must therefore be evenly compacted through proper tamping. In our cafés, this is done in two steps. The first is leveling the grounds. This is done with a leveling tool placed on top of the grounds in the portafilter. Don’t press too hard, or the water won’t be able to flow through and your espresso will be over-extracted.

Step 3: Tamping

After leveling the coffee grounds with a tamper, it’s time to use the tamper. In our café, we use an electric one, but a manual tamper is perfectly sufficient for home use. Make sure the tamper fits your portafilter, as they come in different diameters. The same rule applies here: don’t press too hard, but don’t press too lightly either. It may take a few tries before you get a feel for how much pressure to apply so that your espresso isn’t over- or under-extracted.

Step 4: Inserting

Now place the portafilter—with the tamped, evenly distributed coffee puck—into the brew group of your espresso machine. This is where the final mistake often occurs, one that can ruin even the best preparation: Insert the portafilter slowly and straight into the holder. If you force it or are unsteady, you might not hit the brew group right away. If you’re unlucky, this alone could cause the puck to loosen at the edge of the portafilter, creating a channel through which the water can flow unimpeded. So: Slow and steady wins the race, as the saying goes.