How to Judge Coffee Grounds Quality by Shape: What Causes Coffee Bed Fractures After Pouring

Understanding Coffee Bed Crater Formation

After brewing coffee, many people have the habit of observing the coffee bed crater. If the crater wall is complete and evenly thick, they subconsciously feel that this brew was successful; if the crater shows "abnormalities," they begin to reflect on which stage of the brewing process wasn't executed well. FrontStreet Coffee noticed when discussing brewing with friends that their coffee bed crater not only failed to form a sufficiently high "wall," but most of the coffee grounds had deposited at the bottom. After the coffee liquid finished dripping, the exposed coffee bed and the relatively low wall formed a clear two-section appearance—what we call layer separation.

Too Small a Pouring Circle

Coffee bed craters with layer separation are typically produced by "conservative" coffee brewers. In their pursuit of caution, they're accustomed to using small water flow throughout the entire process, concentrating the water stream within a small circle until the target water volume is reached, fearing that uncertain factors they introduce might ruin a cup of coffee. However, coffee brewed under such "rigorous control" is likely to have concentrated flavors and an overly muted mouthfeel.

Due to the direct impact of the water stream on the coffee grounds in the center area of the filter cone, continuous acceleration of tumbling occurs, greatly increasing the contact area between coffee grounds and water. Meanwhile, the coffee grounds on the periphery that haven't been scoured by the water stream will adhere to the filter paper edges, forming thick walls. This leads to an unbalanced extraction with high extraction rates in the center and low extraction rates on the periphery.

Center Water Addition at the End

Another common case of "broken" crater walls comes from brewers who are the opposite of the "conservative" type. They prefer a more "relaxed" approach to controlling brewing parameters, keeping their eyes only on circling the filter cone and stopping the pour when they feel it's about right. Finally, they discover that the scale reading hasn't reached the target water weight, so they add water to the center.

The water stream agitation in the early stages has already pushed the coffee grounds into uniform distribution. Under the final impact of the center water stream, particles will float up again, and the crater walls submerged by the water level will also sink to the bottom, eventually forming the two-section appearance. The end-stage pouring action mostly occurs after more than a minute and a half, when the denser coffee particles have already settled to the bottom, obstructing water flow. When the water level drops later, it's likely to cause water pooling, resulting in bitter flavors.

How to Avoid Layer Separation?

If you want to extract coffee flavors while maintaining stability, FrontStreet Coffee suggests continuously expanding your pouring circle from the center outward after the bloom ends. As the water level rises, use the water stream to scour all the coffee grounds to ensure even extraction. As the liquid level rises, fewer coffee grounds will be able to adhere to the filter paper. At this point, you can simply pour concentric circles along the radius at half the liquid level.

The higher the water stream, the stronger its penetrating power and the more intense the scouring of the coffee grounds layer; conversely, the lower the water stream, the gentler the force and the less tumbling of the coffee grounds layer. FrontStreet Coffee typically maintains a water stream height of 3-4cm when brewing coffee—not because this height produces the best-tasting coffee, but because at this height, the probability of accidents is minimal, making it easier to master and reducing the impact of human factors on extraction.

Within a predetermined brewing framework, to extract the ideal coffee flavor, we should try to strictly follow the brewing plan while focusing on adjusting various variables. If each parameter deviates slightly, the substances released from the coffee will certainly differ from the preset, and the final flavor feedback will naturally show significant differences.

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