Roast & extraction

The initial pour on a pour-over: just enough water to wet the grounds and let trapped CO₂ escape before the main brew begins, typically 30 to 45 seconds.

The ratio of dry coffee to water (or finished beverage): e.g. 1:16 for a typical pour-over, 1:2 for a normale espresso.

Also: ratio

A defect in espresso where pressurized water forces a path through a weak spot in the coffee puck, leading to uneven, sour, under-extracted shots.

The reddish-brown foam layer on top of a freshly pulled espresso: emulsified coffee oils, dissolved CO₂, and tiny bubbles, typically 2 to 4 mm thick.

Coffee roasted to or past second crack, dark brown to nearly black, oily on the surface, with smoky and bittersweet flavors that dominate origin character.

The mass of dry ground coffee loaded into the portafilter basket before brewing, typically 18 to 20 g for a modern double espresso.

Very small particles produced by grinding, far smaller than the target grind size, that cause uneven extraction and bitterness if not controlled.

Coffee roasted only until just after first crack, pale brown in color, with bright acidity and clear origin character.

Coffee roasted past first crack but stopped short of second crack, medium-brown, balanced between acidity and roast-driven sweetness.

A brief, low-pressure water soak applied to the espresso puck before full 9-bar pressure begins, improving extraction evenness and reducing channeling.

A measurement of how much coffee solids are dissolved in a brewed cup, read with a refractometer and used to calculate extraction yield.

Also: TDS

The mass of liquid espresso that ends up in the cup, typically 36 to 40 g for a 1:2 ratio double shot from an 18 to 20 g dose.

Also: brew yield