Brewing Terms
Basket: The perforated metal cup inside the portafilter that holds the ground coffee. Baskets come in different sizes (single, double, triple) and styles (pressurised and unpressurised). Most home baristas use an 18g double basket.
Blonding: When the espresso stream turns pale yellow toward the end of extraction. This indicates the easily soluble compounds have been exhausted and further extraction will pull bitter, astringent flavours. Many baristas stop the shot when blonding begins.
Brew ratio: The relationship between the weight of dry coffee in (dose) and the weight of liquid espresso out (yield). Written as dose:yield. A 1:2 ratio with an 18g dose produces 36g of espresso. See our full guide to brew ratios.
Channelling: When water finds weak spots in the coffee puck and rushes through them at high velocity, over-extracting those areas while under-extracting the rest. The result is a shot that tastes both sour and bitter. Caused by uneven distribution, cracked pucks or inconsistent tamp. See troubleshooting guide.
Crema: The golden-brown foam that sits on top of a freshly pulled espresso. Created by CO2 trapped in the coffee being released under pressure and emulsifying with oils. Fresh beans produce more crema. Crema is not a reliable indicator of quality, despite popular belief.
Dialling in: The process of adjusting grind size, dose and yield to produce a great-tasting shot with a new bag of beans. Typically takes 3-5 shots. See our complete guide to dialling in.
Dose: The weight of dry ground coffee placed in the portafilter basket, measured in grams. Most espresso recipes use 16-20g, with 18g being the standard starting point.
Extraction: The process of dissolving soluble compounds from ground coffee using water. Under-extraction produces sour, thin shots. Over-extraction produces bitter, harsh shots. The target is typically 18-22% extraction yield.
Extraction yield (EY): The percentage of the dry coffee's mass that dissolves into the espresso. Measured with a refractometer. 18-22% is generally considered optimal for espresso, based on SCA research.
Flow rate: How fast the espresso flows from the portafilter during extraction. Affected by grind size, dose and tamp pressure. A steady, honey-like flow is ideal. Gushing indicates too coarse. Dripping indicates too fine.
God shot: Slang for a perfect espresso. Balanced sweetness, complex acidity, full body, long finish. The shot that makes you stop and pay attention.
Lungo: An espresso pulled at a longer ratio (1:2.5 to 1:3+). More diluted than standard espresso with lighter body and higher clarity. Good for exploring acidity in light roasts.
Pre-infusion: A period of low-pressure water contact before full 9-bar extraction begins. Gently saturates the puck to promote even extraction. Some machines do this automatically. Duration ranges from 2-10 seconds.
Puck prep: Everything you do to the ground coffee before extraction: distribution, levelling, tamping and any other techniques. Good puck prep prevents channelling. Common tools include WDT, distribution tools and calibrated tampers.
Pull: To make an espresso shot. "Pulling a shot" dates back to lever machines where the barista pulled a lever to create pressure.
Ristretto: A restricted shot pulled at a shorter ratio (1:1 to 1:1.5). More concentrated, heavier body, more sweetness. Popular in milk drinks.
Shot time: The duration from pump activation to reaching target yield. Typically 25-35 seconds for standard espresso. Shot time is the result of grind size and dose, not a variable you set directly.
Sink shot: A shot pulled to waste. Used to purge old grounds from the grinder or to dial in when the first shot is expected to be bad.
Tiger striping: Alternating dark and light stripes visible in the espresso stream during extraction. Generally indicates even extraction and a well-prepared puck.
Yield: The weight of liquid espresso in the cup, measured in grams. Together with the dose, it determines the brew ratio.
Grinder Terms
Burrs: The two abrasive surfaces inside a grinder that cut coffee into particles. Available in flat and conical geometries. Flat burrs produce more uniform particles. Conical burrs produce a wider distribution with more body. See our grinder buying guide.
Conical burrs: A cone-shaped inner burr spinning inside a ring-shaped outer burr. Produce a bimodal particle distribution. Generally quieter and cooler-running than flat burrs. Lower retention.
Flat burrs: Two parallel disc-shaped burrs facing each other. Produce a more unimodal (uniform) particle distribution. Higher clarity in the cup. Generate more heat. Common in commercial grinders.
Fines: Very small coffee particles produced during grinding. Some fines are inevitable. Excessive fines can clog the puck and cause channelling. Natural-processed coffees tend to produce more fines.
Grind size: How fine or coarse the coffee is ground. Espresso requires a fine grind (similar to fine sand). The most impactful variable in espresso brewing. See our grind size guide.
Retention: Ground coffee trapped inside the grinder from previous doses. Mixes with fresh grounds and degrades flavour consistency. Low-retention grinders (under 0.5g) are preferred for home use.
RPM: Revolutions per minute of the burrs. Higher RPM grinds faster but generates more heat. Lower RPM is quieter and cooler. Most home grinders run at 1,200-1,800 RPM.
Single-dosing: Weighing the exact amount of beans before grinding, rather than using a hopper. Eliminates retention issues and makes switching between beans easy. Requires a low-retention grinder.
Step size: The smallest grind adjustment a stepped grinder can make. Smaller steps give finer control. Stepless grinders offer infinite adjustment. Puck Yeah lets you set your grinder's step size so that recommendations match your hardware.
WDT (Weiss Distribution Technique): Using a thin needle or set of needles to break up clumps and distribute grounds evenly in the basket before tamping. The single most effective technique for preventing channelling.
Bean and Roast Terms
Blend: A coffee made from beans sourced from multiple origins. Designed for consistency and balance. Most traditional espresso is brewed with blends.
Degassing: The release of CO2 from freshly roasted coffee. Most intense in the first 3-5 days post-roast. Excessive CO2 causes uneven extraction and bubbly crema. Most espresso beans benefit from 7+ days of rest.
First crack: An audible popping sound during roasting when internal moisture turns to steam and expands the bean. Light roasts are pulled at or just after first crack.
Fresh crop: Coffee beans from the most recent harvest. Fresher green coffee generally produces more vibrant, complex roasted coffee.
Natural process: A coffee processing method where the whole cherry dries around the bean. Produces fruity, sweet, full-bodied coffee with more complexity and unpredictability. See our bean origins guide.
Roast date: The date the coffee was roasted. Critical for freshness. Espresso is best 7-21 days post-roast. Puck Yeah tracks roast dates automatically in the Bean Library.
Second crack: A second round of cracking during roasting, occurring at higher temperatures. Beans roasted into second crack are considered dark roast. Oils begin to appear on the surface.
Single origin: Coffee sourced from one farm, region or lot. Showcases the terroir and processing of a specific place. More variable than blends but can be more distinctive.
Specialty coffee: Coffee scoring 80+ points on the SCA scale (out of 100). Evaluated by certified Q graders on aroma, flavour, acidity, body, balance and aftertaste. Represents roughly 10-15% of coffee produced globally.
Terroir: The environmental factors that influence a coffee's flavour, including altitude, soil, climate and shade cover. Higher altitude generally produces denser, more complex beans.
Washed process: A coffee processing method where the fruit is removed before drying. Produces cleaner, brighter, more transparent coffee. The most common processing method globally.
Equipment Terms
Bottomless (naked) portafilter: A portafilter with the bottom cut away, exposing the basket. Allows you to see extraction directly, diagnose channelling and observe tiger striping. A valuable diagnostic tool.
Distribution tool: A spinning device that levels ground coffee in the basket before tamping. Creates a flat, even surface. Not a replacement for WDT but can complement it.
E61 group head: A thermosyphon-based group head design introduced by Faema in 1961. Found on many prosumer espresso machines. Known for temperature stability and pre-infusion capability.
Group head: The part of the espresso machine where the portafilter locks in and water is delivered to the coffee. Contains the shower screen, gasket and dispersion block.
Leveller: See distribution tool.
PID: Proportional-Integral-Derivative controller. An electronic temperature controller that maintains precise brew temperature. Essential for consistent espresso. Most modern machines include PID control.
Portafilter: The handled device that holds the basket and locks into the group head. Available in 54mm, 58mm and other sizes. 58mm is the industry standard for prosumer machines.
Pressure gauge: Displays the brewing pressure, typically in bars. Standard espresso pressure is 9 bars (approximately 130 PSI). Some machines include OPV (over-pressure valve) adjustment.
Shower screen: A perforated metal disc inside the group head that distributes water evenly over the coffee puck. Should be cleaned regularly to prevent clogs and uneven flow.
Tamper: A tool used to compress ground coffee in the basket. Calibrated tampers apply consistent pressure (usually 15-20 lbs). The goal is a level, evenly compressed puck.
Tasting Terms
Acidity: A bright, tangy quality in coffee. Not the same as sourness (which is a defect from under-extraction). Desirable acidity is described as crisp, juicy, vibrant or sparkling. Common in washed African coffees.
Aftertaste (finish): The flavour that lingers after swallowing. A long, pleasant finish is a sign of quality. Bitter, dry or ashy aftertaste indicates over-extraction.
Body: The physical weight and texture of the coffee in your mouth. Ranges from thin and tea-like (light body) to thick and syrupy (heavy body). Influenced by brew ratio, roast level and processing method.
Clean: A coffee with no off-flavours or muddy qualities. Each flavour note is distinct and identifiable. Washed coffees are typically described as clean.
Mouthfeel: The tactile sensation of coffee in the mouth. Related to body but includes qualities like silky, velvety, chalky, gritty or astringent.
Sourness: An unpleasant, sharp acidity caused by under-extraction. Not the same as pleasant acidity. Indicates the need for a finer grind or longer ratio. See our troubleshooting guide.
Sweetness: The perception of sugar-like qualities in coffee. Develops through proper extraction. The sugars and caramelised compounds in coffee require sufficient extraction time to dissolve. Sweetness is the hallmark of a well-dialled shot.
Further Reading
- How to Dial In Espresso puts many of these terms into practice.
- Best Espresso Grinders for Home explains grinder terminology in a buying context.
- Coffee Bean Origins and Processing expands on bean and roast terminology.