Coffee Glossary

A unit of pressure. Espresso is typically brewed at around 9 bars, roughly nine times atmospheric pressure at sea level.

The removable metal cup inside a portafilter that holds the ground coffee puck during extraction.

The initial release of CO2 when hot water first hits fresh coffee grounds, especially visible in pour-over brewing.

Water finding an uneven path through the coffee puck during espresso extraction, causing under- and over-extraction in the same shot.

The reddish-brown foam layer on top of a properly pulled espresso shot, formed by CO2 and oils emulsifying under pressure.

A standardized method for tasting and scoring coffee, used by roasters and graders to evaluate green coffee lots.

The process of adjusting grind size, dose, and extraction time to get a specific espresso shot tasting right on a given machine and bean.

A sourcing model where a roaster buys directly from producers or farms, bypassing traditional import/export intermediaries.

The amount of ground coffee (usually in grams) used for a single shot or brew.

A widely licensed espresso group head design (originally Faema, 1961) known for thermal stability via a heavy metal body.

The process of dissolving flavor compounds out of ground coffee using water, "over-extracted" tastes bitter, "under-extracted" tastes sour/weak.

Unroasted coffee beans, as they arrive from origin before a roaster processes them.

An espresso machine boiler design where a brew-water tube runs through a larger steam boiler, allowing near-simultaneous brewing and steaming after a brief temperature-surfing step.

Proportional-integral-derivative controller, an electronic temperature control that holds boiler temperature within a very tight range, improving shot-to-shot consistency.

The handled fitting that holds the basket of ground coffee and locks into the espresso machine's group head.

The compacted disc of used coffee grounds left in the portafilter basket after pulling a shot.

A "restricted" espresso shot pulled with less water than standard, producing a smaller, more concentrated result.

A group head design (used by La Marzocco, among others) that stays permanently filled with hot water from the boiler for maximum thermal stability.

Coffee sourced from one specific country, region, or farm, as opposed to a blend of multiple sources.

A commercial espresso machine that doses water by volume automatically per shot, common in high-throughput café settings.

The weight or thickness a coffee feels like in the mouth, from light and tea-like to heavy and syrupy, distinct from flavor or acidity.

The bright, tangy quality in a cup, not sourness from a flaw, high-grown washed coffees tend to have more of it.

The smallest particles produced during grinding, too much can cause over-extraction and a muddy or bitter cup.

A container with a bar used to knock a spent coffee puck out of the portafilter after pulling a shot.

A portafilter without a spout, showing the espresso stream directly, useful for diagnosing channeling since flaws are visible immediately.

An audible popping stage later in roasting, past first crack, that marks the transition into darker roast levels.

Compressing ground coffee evenly in the portafilter basket before brewing, uneven tamping is a common cause of channeling.

Using a thin tool to stir grounds before tamping, breaking up clumps for more even water flow through the puck.