Espresso is simply hot water forced through finely-ground, tightly-packed coffee under pressure, for a short, controlled amount of time. Everything in a recipe is an adjustment to one of four variables: how much coffee you use, how fine you grind it, how hard you pack it, and how long the water runs through.

The standard starting ratio

Specialty coffee commonly uses an 18g dose in, roughly 36g of liquid espresso out, over about 25–30 seconds, as a reliable default before adjusting to taste. Think of these as a starting point to dial in from, not a fixed rule — beans, roast level and machine all shift the ideal slightly.

~18gdose in
~36gyield out
25–30sextraction time

Grind size and freshness

Espresso needs a much finer grind than drip or French press coffee — roughly the texture of fine table salt. Pre-ground coffee goes stale within days because grinding exposes far more surface area to air; a built-in or separate burr grinder used right before brewing makes a bigger difference to flavor than almost any other upgrade.

Tamping

Tamping compresses the grounds into an even, level puck so water can't find an easy, uneven path through it. The goal is a flat, firm, level surface — consistent tamping pressure from shot to shot matters more than the exact amount of force used. This is exactly the step that auto-tamping machines remove, at the cost of letting you fine-tune it yourself.

Reading the shot

Common beginner issues

Channeling — water punching through one weak point in the puck instead of flowing evenly — is the most common cause of a sour, inconsistent shot, and it's almost always a distribution or tamping problem rather than a bean problem. A stalling or painfully slow shot more often points to too fine a grind or an overfilled basket than a faulty machine.

Once the shot itself is dialed in, what you make with it is its own set of decisions — see what separates a ristretto from a lungo, and the milk drinks built on top of either.