This is a collection of terms used in the specialty coffee industry and our working definitions for them. We’ll update this list regularly as the industry grows and changes. Let us know if there are words or phrases you’d like to see added!
Espresso: According to the Specialty Coffee Association “Espresso is an ever-changing extraction medium, and frequent changes in the landscape of specialty coffee profoundly affect how baristas extract espresso and how it is understood.”
In its most commonly understood form, however, espresso is a small amount of coffee, prepared to order, using high pressure and a fine grind, in order to extract in around 20-30 seconds.
Espresso Machine: A machine used to brew espresso by forcing pressurized water through finely-ground coffee.
Commercial: Refers to a machine being built with the intention of using it in a commercial entity like a restaurant or coffee shop. Examples include “commercial espresso machine” or “commercial coffee grinder.”
Barista tools: Any of the periphery devices such as tampers, tamp mats, shot glasses, brushes, etc. which are used by baristas to prepare coffee and maintain the equipment they use to do so. May also be called espresso tools.
Boiler: The component in an espresso machine that heats water to the appropriate temperature for brewing.
Steam Boiler: The component in an espresso machine that heats water to the appropriate temperature for steaming milk.
PID: Short for "Proportional-Integral-Derivative," a PID controller is a device that helps regulate and maintain precise water temperature in an espresso machine.
Auto Volumetric: Refers to an espresso machine that automatically controls the volume of water used for each shot.
Valve: A device used to control the flow of water or steam in an espresso machine.
Needle Valve: A small valve that controls the flow rate of water in an espresso machine. Used to control the extraction of coffee by slowly wetting the coffee bed and/or reducing pressure at the end of brewing.
Pressure Profiling: The ability to vary the pressure during the extraction process to optimize the flavors in espresso.
Wand: Also known as a steam wand or milk frothing wand, it is a metal tube attached to an espresso machine using steam to heat and texture milk for drinks.
Group Head: The part of an espresso machine where the portafilter attaches and water is forced through the coffee grounds
Portafilter: A handle with a removable filter basket that holds the coffee grounds during espresso brewing. Produced in many different diameters, e.g. 54 or 58mmto match differently sized group heads. May be spouted or “bottomless” without spouts.
Basket: Also called Filter Basket. The removable part of the portafilter which has coffee placed in it. Comes in different sizes (diameter) e.g. 54 or 58mm, to match the portafilter. Also produced with different depths to accommodate different amounts of coffee, e.g. 16, 18, or 20 grams.
Blind basket: an insert that replaces the basket and has no holes, used for cleaning the grinder.
Backflush: The process of cleaning the espresso machine's group head and valves by forcing water through the machine using a blind basket.
Gasket: A silicone or other material ring which creates a seal inside the group head. The most commonly replaced wear part of an espresso machine.
Purge: part of cleaning or preparing steam wand. A short blast of steam sent through the wand to clear any condensed water or milk left behind. May also refer to purging a coffee grinder, where some coffee is ground out and discarded, especially after changing grind size or while cleaning.
Grinder: A device used to grind coffee beans into the desired consistency for brewing.
Grind by time: A timer built into the grinder which allows the user to set a specific time for grinding. Less accurate than grinding by weight.
Grind by weight (GbW): A scale is built into the grinder, so that a user can request specific weights to be ground on demand, rather than relying on sight or time.
Burrs: The cutting surfaces inside a coffee grinder that grind coffee into uniform particles. They are made of different materials like steel and ceramic and are produced using different manufacturing methods which affect their longevity and the grind qualities they produce. There are two general shapes of burrs, conical and flat. Burrs are generally replaceable within the grinder.
Conical Burrs: A pair of burrs used to grind coffee, one a cone, the other a ring. One of these burrs is held static while the other rotates to grind coffee. These burrs will have a bimodal grind distribution. Bimodal is used to mean that, in a given grind distribution, there are two groups of sizes, one smaller, one larger, due to the shape of the grinding burrs.
Flat burrs: A pair of burrs in a disc shape, usually identical to each other, which coffee is pressed between in order to grind it. These will produce a more unimodal grind size, meaning that the range of grind sizes is more closely grouped together, with fewer fines and boulders.
Stepped/Stepless: referring to coffee grinders, this describes the adjustment of grind size. Stepped grinders have pre-defined setting points, whereas stepless grinders can be set anywhere along the range.
Disk distance detection (DDD): A measurement that some grinders are able to display, which shows the distance between burrs. Allows users to standardize and repeat grind size across multiple grinders.
Fan: A component in some coffee grinders that helps cool the beans or remove chaff.
Retention: The amount of coffee grounds that remain in a grinder's chute or burrs after grinding, which can affect flavor consistency.
Boulders and Fines: Terms used to describe uneven coffee particle sizes after grinding. Boulders are larger particles, while fines are smaller.
Clumping: The formation of coffee grounds into clumps or aggregates, often due to static electricity or improper grinder settings. This can be a sign that the grinder needs cleaning or that the coffee should be ground coarser.
Brew Methods: Different techniques used to prepare coffee, such as pour over, batch brew, or immersion.
Percolation: the movement of water through a bed of ground coffee. Batch or drip brew and pour over are all examples of percolation brewing.
Pour over: A brewing method where hot water is poured manually over coffee grounds. Examples include the Hario V60, Kalita Wave, Chemex.
Immersion: A brewing method where coffee grounds are fully immersed in water for a specific period before separating the liquid from the grounds.
Press: This may refer to French press or Aeropress brewing methods, both variations of immersion brewing
Extraction: The process of dissolving and extracting flavor compounds from coffee grounds using water. It refers to the extraction of soluble compounds, such as oils, sugars, acids, and aromatics, during the brewing process. The goal of extraction is to achieve a balanced and flavorful cup of coffee by controlling variables like water temperature, brew time, grind size, and coffee-to-water ratio.
Under-extraction: Less than ideal brew which results in weak and sour coffee. Usually resolved by making the grind size finer.
Over-extraction: Longer than ideal contact time or greater than needed agitation which produces bitter and astringent flavors. Usually resolved by making the grind size coarser.
Channeling: the process of water flowing through only part of a coffee bed, leading to both under-extracted and over-extracted flavors being present in the drink.
Zero Bypass: A brewing method that aims to avoid channeling which allows water to pass through the coffee bed without proper extraction.
Bypass water: water that is intentionally added after brewing to adjust the coffee/water ratio. The most classic example is the americano, though bypass is a more modern term in specialty coffee.
Gooseneck: refers to the spout on a kettle, which is placed at the bottom of the water reservoir, with a tip at the top. This curved shape allows for greater control in brewing pour-overs, allowing the user to place limited amounts of water in targeted areas.
Tamper: A tool used to compress coffee grounds evenly in the portafilter before brewing.
PUQpress: A brand of automatic tamper that provides consistent tamping pressure.
Knockbox: A container used to collect and dispose of used coffee grounds. Robustly built to withstand the pressure of a portafilter striking it to release a compressed puck of coffee grounds.
Brushes: Cleaning brushes used to remove coffee residue or grounds from equipment.
Bean: A single coffee seed or the general term used to refer to coffee in its unground form.