Скачать или смотреть Pour-Over Physics: Mastering Flow Rate, Hydraulics | The Scientific Goal of Brewing

Stop calling it "drip coffee!" Pour-over is a controlled experiment governed by Fluid Dynamics, Hydraulics, and Thermal Energy. We break down the four invisible forces that determine your cup's fate—from achieving the perfect 18–22% extraction yield to managing the CO2 explosion in the mandatory Bloom Stage.

⚛️ The Controlled Experiment: Pour-over is not just pouring water over grounds; it's a precise application of science. The ultimate goal is to achieve laminar flow and even saturation to uniformly dissolve soluble compounds, hitting that sweet spot of 18 to 22 extraction yield. Any failure to balance the core variables results in weak, sour under-extraction or bitter, astringent over-extraction.We dissect the physics of the brew bed and provide the technical blueprint for the perfect V60 or Chemex brew.

Time,Topic
0:00,The Physics Hook: The Goal of 18–22% Extraction
1:15,Variable 1: Hydraulic Resistance (Grind Size and Permeability)
2:40,Variable 2: Flow Rate (ml/sec) and Extraction Kinetics
4:05,Variable 3: Thermodynamics (92∘C to 96∘C Window)
5:30,Variable 4: Turbulence (Agitation vs. Channeling)
6:55,The Bloom Stage: CO2​ Management is Mandatory
8:20,The CO2​ Barrier: How Off-Gassing Blocks Water
9:45,Technique: Gooseneck Kettles and the Pulsing Pour
11:10,"Recipe CCPs: Ratio, Temperature, and Total Contact Time"

The Four Core Physics VariablesPour-over
success relies on mastering these four invisible forces
1:Hydraulic Resistance: This is the drag created by the coffee bed. It determines the permeability coefficient k of the bed and is controlled by your grind size. Too much resistance causes stalling; too little causes rushing.
2:Flow Rate ml/ sec: Controlled by your kettle spout design and pour angle, flow rate dictates extraction kinetics and contact time. A slower flow rate increases contact time for higher extraction.
3:Turbulence: The mechanical agitation caused by the pour. Light turbulence is beneficial, promoting saturation, but excess turbulence creates micro-channels, leading to severe under-extraction.
4:Thermodynamics (Temperature): The ideal range is 92°C - 96°C. Temperature dictates the solubility of acids, sugars, and aromatics. Temperature also influences water's viscosity, which impacts flow speed.

The Chemistry of the Bloom StageThe first 30 seconds are the most critical. Freshly roasted coffee contains 1%–2% trapped CO2 (a product of the Maillard reaction).The Barrier: When hot water hits, the CO2 rapidly off-gasses, creating a hydrophobic barrier that physically prevents water from touching the grounds.The Technique: Use a precise 2:1 water-to-coffee ratio (e.g., 40g water for 20g coffee). Allow 30–45 seconds for degassing, stabilizing the bed for uniform extraction.

The main pour requires precise control. We advocate for the Pulsing Pour Technique using a gooseneck kettle to maintain laminar flow and manage agitation.

Final Recipe Control Points: We provide the scientific targets for reproducible success: Ratio 1:15 \ 1:16, Temperature 93°C, and Total Contact Time 3:00 to 3:30 \ minutes.

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