To those whose only coffee-making experience has been with brewing methods other than espresso, the remarks below concerning the importance of the correct grind in espresso will doubtless sound like the mutterings of a French omelet cook, even an obsessive French omelet cook. So be it, because grinding the coffee may be the single most important act in the entire sequence of espresso brewing events.
Recall that the heavy body and rich flavor of espresso coffee is achieved through pressure and resistance: pressure by the brewing water, and resistance to that pressure by a uniform layer of compressed, ground coffee. The hot water, under great pressure, does its best to push its way through the layer of ground coffee, but owing to the resistance of the finely-ground and highly-compressed coffee, it cannot succeed until it has saturated every grain of the coffee, extracting the coffee’s entire flavor and perfume almost instantly, and delivering it intact into the cup. This perfectly poised opposition of pressure and resistance is at the heart of the espresso brewing system.
