Espresso extraction relies on pressure-driven flow through a porous coffee puck. Water pressure interacts with grind size, puck density, and resistance to determine flow rate and extraction yield.
Too much resistance causes channeling, while too little leads to under-extraction. Pressure profiling allows baristas to adjust pressure over time, improving balance and reducing defects.
Understanding espresso as a fluid dynamics problem improves consistency far more than recipe memorization alone.
