Old physics models (pre-2020) assumed that uniform particle size leads to uniform extraction.
A consistent particle size distribution leads to uniform extraction. Too wide a range, and your brew is simultaneously sour (under-extracted boulders) and bitter (over-extracted fines).
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At the end of the brew, a significant amount of liquid remains trapped in the coffee bed. This is caused by capillary action—the ability of a liquid to flow in narrow spaces against gravity due to surface tension and adhesive forces.
Using pulsed pours (e.g., 5 equal pours every 30 seconds) increases macroscopic agitation without raising temperature. This disrupts the boundary layer of saturated water around each particle, boosting extraction efficiency by 15–20% compared to a single continuous pour. the physics of filter coffee epub updated
The flow of water through a coffee bed is governed by , which relates the flow rate to the pressure drop, permeability, and viscosity.
: The book explores how soluble compounds move from the coffee grounds into the water, examining the role of temperature and contact time. Percolation and Flow
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The book is structured into 11 chapters, moving from chemical foundations to advanced fluid dynamics: Extraction & Water Chemistry Old physics models (pre-2020) assumed that uniform particle
Proper agitation and even pouring are required to maintain a uniform bed structure. 3. Particle Size Distribution and the Physics of Grinding
) is the most volatile variable in this equation. It is determined by how tightly the coffee particles are packed and their physical size. If the grind is too fine, or if the grounds settle into a highly compacted state, permeability drops significantly. This slows the flow rate ( ), which can lead to over-extraction and bitter flavors. Particle Size Distribution and Surface Area
is the pressure drop across the bed (driven by gravity in pour-over methods). (mu) is the dynamic viscosity of water. is the height of the coffee bed. Permeability and Fine Particle Migration Permeability (
Temperature dictates the kinetic energy of water molecules. Higher temperatures increase the diffusion coefficient ( ), causing compounds to dissolve faster. To help tailor any further scientific analysis, let
The book emphasizes using high-quality burr grinders to minimize the range of particle sizes, promoting a more uniform extraction. 3. Water Chemistry and Thermodynamics
Despite the heavy science, the book is grounded in reality. A review on Amazon notes that it is easy to figure out how to improve your coffee because Gagné breaks down each variable and shows how they are all related.
The Physics of Filter Coffee : Jonathan Gagne: Amazon.de: Books
Water immediately dissolves the highly accessible soluble compounds on the exterior of the ground particles. This happens almost instantly upon contact.