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Why Does the Used Coffee Bed Split into Two Layers?

Published: 2026-01-27 Author: FrontStreet Coffee

Last Updated: 2026/01/27, Last week, we discussed why pour-over coffee requires circular water pouring. We learned this technique improves extraction efficiency while preventing water from flowing chaotically, helping establish a controlled flow path to achieve uniform extraction. When the used coffee grounds form a "bowl-shaped" pattern, with the grounds along the filter cup's edge creating a distinct layer from the bottom, it's often a sign of your brewing technique. This separation indicates that water has flowed through the coffee bed in a way that created channels, potentially leading to uneven extraction. Understanding this phenomenon helps coffee enthusiasts refine their pouring technique for better extraction consistency.

Understanding Pour-over Coffee: The Importance of Circular Pouring

Last week, we discussed why circular pouring is essential in pour-over coffee brewing. We learned that this technique improves extraction rates while preventing water from flowing chaotically, helping it follow a defined path to achieve even extraction. When the coffee grounds after brewing form a "bowl shape," with the edge grounds and bottom creating a smooth, gentle slope, this indicates that the circular pouring process has achieved relatively ideal flow control.

Bowl-shaped coffee grounds after proper pour-over brewing

Common Issues with Coffee Ground Beds

Recently, some beginner coffee enthusiasts have found that their pour-over coffee doesn't taste quite right, and the appearance of their spent coffee grounds doesn't match what they see in tutorials. They asked FrontStreet Coffee what might be causing this issue. The "coffee bed" shared by this friend looked like this: the ground wall on the filter cup was clearly broken into two sections, with a thin circle of grounds in the middle containing small bubbles and almost no particles. Some coffee grounds had been washed to the bottom, similar to the image below.

Improperly formed coffee grounds bed with broken sections

Understanding the Causes: Pouring Technique Issues

This type of coffee grounds issue likely stems from pouring technique. The main reason for the ground wall breaking into two sections is excessive water flow force toward the end of brewing. Let's imagine what happens: after the bloom phase, when you pour the second segment of target water into the filter cup according to your brewing plan, the stirring action of the water column causes coffee grounds to float wherever the liquid surface touches. As the liquid level gradually drops, surface particles stick to the filter paper, forming a ground wall of consistent thickness.

Properly formed coffee grounds wall during brewing

When the liquid level drops to 2/3 of the filter cup height, if you impatiently use a large water flow while circling widely to pour the final segment, the overly forceful water column will break through the previously constructed wall. This segment of coffee grounds gets washed down, creating the broken appearance. If you continue pouring water into the broken section, hot water will directly pass through the filter paper and flow away from the cup's ribbed edges, causing "channeling effect" - uneven extraction. This explains why the coffee brewed by this friend tasted off.

Other Common Pouring Issues

Besides broken sections, there are other situations caused by excessively wide circular pouring. These coffee beds look like this:

Coffee grounds bed with uneven edges due to over-pouring

This type of coffee grounds bed usually occurs because the liquid level in the later stages completely submerges the previously built ground wall. Although it doesn't reach the filter paper, the overflowing water flows directly away from the ribbed edges, causing under-extraction or reduced concentration. Meanwhile, the fine particles washed to the bottom may clog the filter paper, causing water pooling. The indicators are scattered coffee particles on the uppermost part of the coffee bed, extraction time typically exceeding 2 minutes and 10 seconds, and the coffee having an unpleasant bitter taste.

Over-extracted coffee with clogged filter paper

FrontStreet Coffee's Recommended Techniques

Many brewers have likely encountered these two situations during their beginner days. To improve coffee taste while enhancing extraction techniques, FrontStreet Coffee recommends adopting a steady approach to master the fundamentals of flow control. The higher the water flow, the stronger the penetrating force and the more intense the washing of the coffee ground layer; conversely, the lower the water column, the gentler the force and the less tumbling of the coffee ground layer. Understanding this principle, we can appropriately adjust water flow and circle size according to different pouring stages.

Three-stage pour-over technique demonstration

Take FrontStreet Coffee's commonly used three-stage method, for example. After the bloom phase, we first use steady, vertical large water flow, maintaining a distance of 3-4cm from the liquid surface while circling evenly to wash the ground layer. Starting from the center and moving outward in a clockwise direction, we continuously expand the range until the scale shows 125 grams.

As the liquid level rises, fewer coffee grounds can adhere to the filter paper. When the water level drops to halfway, you can circle along half the radius of the liquid surface in concentric circles, gently pouring with a small water flow of 2cm height. This approach allows all particles in the filter cup to receive equal attention, fully releasing flavor compounds while effectively preventing the previously constructed ground wall from being washed down, which would cause uneven extraction.

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FrontStreet Coffee

No. 10 Bao'an Qianjie, Yandun Road, Dongshankou, Yuexiu District, Guangzhou, Guangdong Province