What are the Symptoms of Channeling in Pour-Over Coffee? Solutions for When Channeling Occurs

Channeling is a phenomenon that FrontStreet Coffee frequently discusses in relation to espresso extraction. However, channeling doesn't only occur in espresso extraction—it also happens in pour-over coffee, you just might not notice it.

What is Channeling?

Following our usual approach, FrontStreet Coffee will explain what "channeling" actually is. In the ideal model of coffee extraction, water passes completely through the coffee grounds and extracts coffee substances, ideally without wasting a single drop. However, water has a characteristic: it's lazy and always chooses the path of least resistance.

Using espresso as an example, when we properly distribute and tamp the coffee grounds, the coffee puck blocks all the easy paths, forcing water to pass through the coffee grounds obediently. This prevents any water from escaping.

But if the coffee distribution is uneven and the puck density is inconsistent, water will more easily break through the sparse areas during extraction, forming perforated channels. Subsequent water will then flow through these channels, resulting in under-extracted coffee. As shown in the red-circled parts of the image, due to channeling, large amounts of water spray out from perforations, and the resulting coffee liquid will be lighter in color than normal.

Severe channeling will leave perforation marks on the coffee puck.

Does Channeling Occur in Pour-Over Coffee?

In fact, all filter-based extraction methods carry the risk of channeling. FrontStreet Coffee discusses it more in espresso because channeling has a significant impact on the flavor and mouthfeel of espresso. While channeling in pour-over coffee does affect flavor and mouthfeel, it's far less severe than in espresso.

If you observe an incomplete coffee bed wall after brewing, this indicates that channeling was quite severe. FrontStreet Coffee uses the V60 as an example. The V60 dripper has spiral ribs that lift the filter paper to prevent over-extraction from prolonged soaking. However, this lifting has a drawback: water can easily flow along these ribs. But if there's a layer of coffee grounds adhering to the filter paper edge, then even if water flows along the ribs, it must still pass through this layer of coffee grounds to reach the bottom.

If you find that the coffee bed wall is incomplete, it means some water didn't pass through the coffee grounds but flowed directly from the edge of the dripper—this is channeling.

More severe channeling occurs when water hits the filter paper during pouring, breaking through the original coffee bed wall.

The situation shown above occurs because the water stream had an arc during pouring. Although the surface coffee bed wall wasn't broken during pouring, the arc caused the lower part of the coffee bed wall to break. Large amounts of water will then flow away from here, resulting in coffee that is weak, astringent, and contains harsh flavors.

Of course, even if the coffee bed wall isn't broken after brewing, it doesn't mean channeling didn't occur. If you continuously pour in large circles, the impact of the water stream during brewing might cause channeling. However, when the coffee liquid level drops later, the surface coffee grounds adhere to and cover the perforations at the edge, making it appear undamaged.

Another Type of Channeling

Another slightly milder form of channeling is when water flows over the coffee bed wall. This situation often occurs with light-roasted coffee beans. Light-roasted coffee beans have denser fibers and fewer particles floating on the surface. Therefore, when the liquid level rises to a certain point, there aren't enough coffee grounds to form the bed wall, creating voids. However, this only affects the uppermost layer of water. As long as the liquid level remains below that area, there's no problem. But the lost water is like youth gone by—it cannot be recovered.

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