The Physics Of Filter Coffee Pdf

When you pour water from a gooseneck kettle into a coffee bed, you are injecting kinetic energy into a porous medium. The physics begins with the jet break-up.

Filter coffee is not magic—it is applied physics. Every aroma, sweetness, or bitterness in your cup results from how heat, water, and ground beans interact. This guide strips away marketing myths and focuses on measurable, repeatable principles.

Core premise: Extraction = Mass dissolved from grounds / Total dry coffee mass. Target: 18–22%.

The rate of chemical reactions (extraction of oils, acids, sugars) is temperature-dependent. This is described by the Arrhenius equation: The Physics Of Filter Coffee Pdf

$$k = A e^-\fracE_aRT$$

In Practical Terms:

Problem: Sour & Weak (underextracted)

Problem: Bitter & Dry (overextracted)

Problem: Long drawdown (>4 min for 250 mL)

Problem: Fast drawdown (<2 min for 250 mL) When you pour water from a gooseneck kettle

As the stream hits the crust of grounds, the Weber number (We) predicts whether the water will penetrate or splash.

For filter coffee, you want We < 10 to avoid droplet formation. A high We (caused by pouring from too high a height) creates micro-droplets that cool below optimal extraction temperature (90–96°C) before even reaching the coffee.

PDF Takeaway: A proper physics PDF will include a Pour Height Nomogram—a chart linking kettle spout diameter, flow rate, and optimal height to maintain laminar, non-splashing flow (typically 3–7 cm above the slurry). The rate of chemical reactions (extraction of oils,

The way water moves through the coffee bed determines how fast the brew finishes and how evenly the coffee is extracted.