Does Tapping the Dripper Affect Coffee Extraction?

A single coffee bean is composed of various flavor compounds, including acidity, sweetness, bitterness, and aroma, each with different dissolution rates—some fast, some slow. To brew a pot of coffee that captures all these flavors without exhibiting the negative tastes of over-extraction, we summarize our past brewing experiences and achieve relatively uniform extraction of each coffee particle in the cup by properly executing "fundamental work."

For example, details such as uniform particle size distribution, steady circular pouring with consistent arc and force, adjusting grind settings according to roast depth, and sieving out some extremely fine particles—all ultimately aim to achieve uniform contact between particles and water. Additionally, FrontStreet Coffee has noticed that many meticulous coffee enthusiasts add the action of "tapping the filter cup" before正式 pouring to make the powder surface as level as possible, unaware that this might be "quietly" changing the uniformity of the coffee powder bed density.

Please observe carefully: this is freshly ground Panama Santos Geisha coffee powder using the EK43s grinder at setting 10. Visually, the powder bed appears relatively uniform and loose, with particle sizes and shapes being relatively consistent. Extremely fine particles adhere to the surface of larger particles due to static electricity, while obvious gaps between coarse particles are interspersed with fine particles.

Subsequently, FrontStreet Coffee gently tapped the filter cup containing the coffee powder about 10 times and observed the state of the powder layer again. The upper layer of coffee powder consists almost entirely of larger particles, with sparse gaps making the powder bed appear fluffier. When we tilted the filter cup to any side, we found that a large amount of fine particles had gathered at the bottom, making this part of the powder bed much more "compacted." This means that the vibration from tapping caused fine particles to fall from gaps to the bottom due to gravity, also changing the density of the powder layer: lower density at the top and higher density at the bottom.

Comparative Experiment

To verify whether the action of "multiple taps" affects coffee extraction, FrontStreet Coffee conducted a simple comparative experiment.

Coffee beans: 15g Panama Santos Geisha
Grind setting: EK43s at setting 10
Filter cup: V60
Coffee-to-water ratio: 1:15
Water temperature: 91°C
Three-stage pouring: 30g, 95g, 100g

No Tapping Group

During the blooming pre-extraction phase, particles absorbed water evenly, forming a regular "dome" to release gas in advance for the formal extraction stage. After the coffee liquid completed dripping, the total extraction time was 1 minute and 58 seconds. The coffee entry is dominated by dark berry notes, accompanied by round textures of brown sugar and sweet orange, with rising acidity.

10 Taps Group

During the blooming stage, the hot water poured into the powder layer wasn't absorbed immediately but instead escaped and flowed to the edge of the filter cup. During subsequent segmented pouring, large bubbles occasionally released, with slight blockage and water pooling in the later stages, totaling 2 minutes and 17 seconds of drip time. The coffee tasted predominantly tea-like, with unremarkable aroma, carrying citrus acidity and faint woody flavors.

From the above, it's not difficult to see that the hot water poured into the powder layer couldn't fully penetrate the powder bed and flow into the lower pot, instead showing "reverse flow" because the powder bed composed of numerous extremely fine particles was too compact. Water is inert—it tends to flow through areas with less resistance when passing through coffee powder. Therefore, compared to the compact extremely fine powder pile, water is more inclined to "find another way out" and overflow to the edges. This results in the powder bed becoming partially moist and partially dry—what we commonly call undesirable blooming, which not only leads to channeling effects but the bubbles released upon encountering water may also hinder the dissolution of other substances, consequently causing uneven extraction.

Recommendations

If you also have the habit of frequently tapping the filter cup lightly, and often experience blockage and water pooling in the final stages of brewing, or suspect that your coffee tastes over-extracted, FrontStreet Coffee suggests first mastering proper powder distribution techniques to reduce the need or frequency of tapping.

Before pouring the powder, you can first check if there's static electricity causing powder to stick to the inside of the powder container. If so, you can gently stir with a spoon to eliminate the static electricity. When pouring coffee powder into the filter cup, simply aim for the center line and pour slowly. This way, the powder particles will first fill the inverted triangular cone, then form a small hill-like peak. At this point, there's no need for multiple taps—just gently shake the filter cup to make the powder layer relatively level, which won't affect the extraction state.

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

Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473