Espresso · 12 min read
Espresso is coffee distilled to its most intense and unforgiving form. In roughly 25 to 30 seconds, pressurized water extracts a concentrated solution from finely ground coffee. There is no hiding in espresso. Every variable matters. Every fraction of a gram, every degree of temperature, every second of contact time is audible in the cup.
The fundamental equation of espresso is the brew ratio: the relationship between the dose and the yield. Modern specialty espresso typically uses ratios between 1:1.5 and 1:2.5. The current consensus hovers around 1:2 — an 18-gram dose yielding a 36-gram shot in approximately 27 seconds. But each coffee demands its own ratio, its own grind, its own temperature.
Grind size is the primary lever for controlling extraction time. Espresso grind occupies a narrow window — fine enough to create resistance against nine bars of pump pressure, coarse enough to allow water to flow without channeling. Channeling — where water finds paths of least resistance through the puck — is the most common defect in espresso preparation.
Water temperature profoundly affects which compounds are extracted. Higher temperatures increase extraction speed and favor bitter compounds. Lower temperatures produce sweeter, more acidic shots. Many modern machines offer temperature profiling, allowing the barista to change temperature during the shot.
Pressure profiling represents the current frontier. Traditional machines maintain a flat nine bars throughout extraction, but pressure-profiling machines allow real-time variation. A popular approach begins with low-pressure pre-infusion, which saturates the puck evenly before full pressure is applied. The fifteen seconds of a well-pulled shot represent a culmination of engineering, agriculture, and craft.