The moment water contacts the coffee ground, it washes over the exposed surface cells that were broken open during grinding. This is a rapid process. The soluble compounds easily dissolve into the moving liquid film and are carried away by the fluid flow. Phase 2: Internal Diffusion
Chapter 10 — Typical Recipes with Physics Rationale
Chapter 18 — Further Reading and References the physics of filter coffee epub work
From a physics perspective, water flow through the coffee grounds can be described by Darcy's law, which relates the flow rate of a fluid through a porous medium to the pressure gradient and the properties of the medium. In the case of filter coffee, the porous medium is the coffee grounds, and the fluid is water.
: Heavy, less polar molecules such as chlorogenic acid lactones, polyphenols, and caffeine dissolve slowly. Prolonged exposure to water shifts the extraction into this phase, causing bitterness and astringency. 3. Thermodynamics of Extraction The moment water contacts the coffee ground, it
Larger fragments (typically 500–1000 microns) that form the structural framework of the coffee bed.
Coffee beans are roasted biological cells. Roasting pockets carbon dioxide inside a brittle, porous polymer matrix. When you grind coffee, you break these cells open. This exposes the soluble compounds trapped inside. Surface Area vs. Diffusion Distance Phase 2: Internal Diffusion Chapter 10 — Typical
If a grind contains too many fines, they settle at the bottom of the filter paper—a phenomenon known as . This clogs the voids, chokes the flow, increases contact time, and leads to over-extraction. 2. Mass Transfer and Diffusion Kinetics