Glossary

Parts & terms

What each part does and how it can fail. Tap a term to read the longer explanation.

326 of 326 terms

1

10-year service: A major overhaul for prosumer machines — replacing gaskets, seals, flow restrictors, shower screens, pump parts, pressurestat and thermostats.

3

3-way solenoid valve: An electromechanical valve that directs water from the pump to the group during extraction, then releases puck pressure to the drip tray when the shot ends.

9

9 bar standard: The industry-standard espresso extraction pressure — 9 bars (about 130 psi, or 9 times atmospheric pressure).

A

ACCC consumer guarantees: The Australian Consumer Law (ACL) that entitles buyers to a product that is of acceptable quality, fit for purpose, and matches its description.
Acoustic/visual dosing cue: A beep or light signal that alerts the barista when a target weight or time is hit.
AeroPress: A plastic plunger brewer invented by Alan Adler in 2005. Uses air pressure to force water through a paper filter into the cup.
AeroPress bypass: Adding water after brewing to dilute to desired strength.
AeroPress inverted method: Starting with the AeroPress upside-down so no water drips out during steep time, then flipping and plunging.
AeroPress standard method: The traditional technique — plunger in filter, coffee in chamber, brew, plunge.
Affogato: A scoop of vanilla ice cream or gelato with a shot of hot espresso poured over.
Agitation: Any disturbance of the coffee grounds during brewing — swirling a V60, stirring a Clever, or the pump turbulence inside a puck.
Americano: Espresso with hot water added after. Originated with US servicemen in WWII Italy who found espresso too strong.
Anaerobic processing: Fermenting cherries in sealed tanks to develop experimental flavours.
Anti-static plate / RDT: A grounded metal plate inside the grinder chute (anti-static), or the technique of spritzing the beans with 1–2 drops of water (Ross Droplet Technique) to reduce static charge.
Anti-Vacuum Valve: One-way valve that lets air into the boiler as it cools to prevent vacuum collapse and pull-back of water.
Arabica: Coffea arabica — the higher-quality, lower-caffeine coffee species responsible for nearly all specialty coffee.
Articulating wand (ball-joint wand): A steam wand with a multi-directional joint, letting you position the tip at any angle and height.
ASCA (Australian Specialty Coffee Association): The Australian affiliate of the Specialty Coffee Association, running national barista, latte art, cup tasters and brewers cup championships.
Auto-purge: A feature on some machines (notably La Marzocco Linea Mini, Rocket R Nine One, higher-end Breville) that automatically purges the steam wand after you finish steaming.
Autofill probe: A stainless probe inside the steam boiler that detects the water level by electrical conductivity, telling the autofill solenoid when to refill.

B

Backflush (clean): Locking a blind basket into the group and running a short brew cycle with espresso machine cleaner, forcing cleaning solution backwards through the three-way valve to flush oils and residue.
Backflush (water only): Backflushing with plain water, with no detergent.
Bar mat: A rubber mat that lives on the bar under the group to catch drips and spills.
Barista champion credentials: Titles awarded at official competitions run by the World Coffee Events (WCE) global body and affiliates like ASCA (Australian Specialty Coffee Association).
Barista milk: A milk formulation (dairy or plant) designed specifically for steaming and textures — usually higher protein and sometimes added stabilisers.
Batch brew: Automated drip coffee — a machine heats water to temperature and delivers it over a larger bed of coffee (usually 500ml–2L).
Bellows: A rubber or silicone bulb that fits over the hopper opening of a single-dose grinder, used to purge residual grounds from the burr chamber.
Blend: Coffee mixing beans from multiple origins for a consistent, designed flavour profile.
Blind disc / blind basket / blanking disc: A solid rubber (or metal) disc that fits into the portafilter to block flow, used for backflushing or OPV adjustment.
Bloom (espresso): The initial swelling and off-gassing of the puck during pre-infusion as CO₂ escapes from fresh coffee.
Boiler: Pressurised vessel that heats water for brewing, steaming, or both.
Boiler material (copper, stainless steel, brass): The metal the boiler is built from. Copper is traditional and thermally efficient; stainless steel is inert and doesn't need descaling as often; brass is used for heat exchangers and some commercial boilers.
Boiler pressure gauge: The manometer that displays steam boiler pressure (0–2.5 bar typical range).
Boiler scale: Calcium carbonate deposits left behind by evaporated water, coating boiler interiors and restricting flow.
Bottomless (naked) portafilter: A portafilter with the spouts and bottom removed, exposing the basket and the underside of the puck during extraction.
Boulders: Oversized particles (500+ microns) produced when burrs can't cut cleanly.
Brew boiler: The smaller, lower-temperature boiler that produces water for espresso extraction — typically held at 90–96 °C.
Brew chart (strength vs extraction): A two-axis graph plotting TDS (strength) vs EY (extraction), with a "sweet spot" box defined by the SCA or the barista's own preference.
Brew pressure gauge: A manometer that reads the actual pressure at the group during a shot.
Brew ratio: The ratio of dose to yield — e.g., 18g in, 36g out is a 1:2 ratio.
Brew temperature: The actual water temperature meeting the coffee during extraction.
Burr: The cutting elements inside a grinder — flat or conical, steel or ceramic — that shear coffee beans into a controlled particle size.
Burr alignment: Making sure the two burrs are perfectly parallel to each other.
Burr chirp: The sound the burrs make when they touch each other with no coffee in between — used to find the zero point.
Burr diameter: The cutting-surface diameter of the burrs — common sizes are 50mm, 58mm, 64mm, 75mm, 83mm, 98mm.
Burr material: The metal or ceramic the burrs are made from — hardened steel, titanium-coated steel, red-speed steel (HSS), or ceramic.
Burr seasoning: The process of running 5–20kg of coffee through new burrs to smooth micro-roughness on the cutting edges.
BWT: Best Water Technology — an Austrian water filter manufacturer widely used in specialty cafés for their magnesium-dosing filters.

C

Capacitor: Energy-storage component used to start vibration pumps and run motors — fails closed or fails open and your machine won't pump.
Cappuccino: A double shot with steamed milk topped with a thick foam layer (traditionally 1/3 espresso, 1/3 milk, 1/3 foam), dusted with chocolate powder in Australia.
Carbonic maceration: A processing method borrowed from winemaking where whole cherries ferment in CO₂-rich tanks.
CE: Conformité Européenne — the European regulatory mark for electrical and pressure equipment.
Channelling: Water finding a path of least resistance through the puck, bypassing most of the coffee and extracting intensely from a narrow zone.
Check Valve: A one-way valve that lets water flow in only one direction. Found on the pump outlet, autofill line and group inlet to stop hot/pressurised water from flowing back where it shouldn't.
Check valve (non-return valve): A one-way valve that prevents water flowing backwards through the system.
Chemex: A glass pour-over brewer with a built-in filter holder and very thick paper filters, invented in 1941.
Choker: A shot that runs far too slow or not at all — grind is too fine, or the puck is over-dosed.
Chute: The channel or tube that guides ground coffee from the burrs out to the portafilter.
Cleaning brush: A brush with stiff natural or nylon bristles used to clean the group head, shower screen, and grinder.
Clever Dripper: A V60-shaped dripper with a valve at the bottom that holds water until the brewer is placed on a cup.
Cloth filter: A reusable fabric filter used on siphons and some pour-overs.
Coffee canister (airtight container): A sealed container (often with a valve or vacuum system) for storing roasted beans.
Coffee scale (barista scale): A precision scale, typically 0.1g resolution, designed specifically for coffee work — waterproof, fast response, with integrated timer.
Cold brew: Coffee steeped in cold or room-temperature water for 8–24 hours, producing a smooth, low-acid concentrate.
Cold drip: A slow cold extraction where ice-cold water drips one drop at a time through a column of grounds over 3–12 hours.
Conical burr: A cone-shaped inner burr and a matching hollow outer ring, grinding beans as they pass between the tapered surfaces.
Cool-touch wand (no-burn wand): A double-walled or insulated steam wand that stays cool to the touch.
Cooling flush: Running water from the group on an HX machine (with no portafilter engaged) to purge steam-heated brew-line water before pulling a shot.
Cortado: Espresso with equal parts lightly-textured warm milk. Spanish origin. Usually served in a 150ml Gibraltar glass.
Cup warmer: An electric plate or passive warmer for pre-heating cups.
Cupping: The standardised protocol for evaluating coffee — grounds steeped in hot water, crust broken, slurped from spoons, scored on a 100-point scale.

D

Dechunker (bean-density declumper): A pop-up screen or sieve that mechanically breaks grind clumps. Sometimes integrated into dosing cups.
Declumper: A wire mesh or perforated screen in the grinder chute that breaks up clumps of ground coffee before they hit the basket.
Degassing: The release of CO₂ from beans in the days following roasting.
Descaling agent: A mild acid (citric, lactic, or phosphoric) used to dissolve limescale from boilers and water paths.
Development time ratio (DTR): The percentage of the roast spent between first crack and drop.
Direct drive vs belt drive: The burr carrier is either attached directly to the motor shaft (direct drive) or connected via a belt (belt drive).
Dispersion block (diffuser): The metal plate above the shower screen that spreads water from the group inlet evenly across the coffee puck.
Dispersion Plate / Block: The thicker plate above the shower screen that distributes incoming water before it reaches the screen.
Dispersion screw: The single screw holding the shower screen (and sometimes dispersion block) onto the group.
Dose (weight in): The mass of dry ground coffee loaded into the basket, measured in grams.
Doser: Chamber with a paddle that delivers a measured dose into the portafilter.
Doserless (on-demand): A grinder that grinds directly into the portafilter on demand, with no intermediate dosing chamber. Usually triggered by a button or a portafilter sensor.
Dosing cup: A small metal cup (often 58mm OD) used to catch grounds from the grinder, then invert into the basket.
Dosing funnel: A magnetic ring or funnel that sits on top of the basket to guide grounds in without spilling, often used with single-dose workflows.
Dosing ring: A magnetic or friction ring that sits on top of the basket to catch loose grounds and guide them in.
Drip tray: The removable basin under the group and steam wand that catches drips, purges and rinse water — usually with a grate on top and either a drain hose out the back or a full-tray indicator.
Drip Tray & Drain: The catch tray under the group plus the drain hose that takes waste water from the 3-way solenoid and the drip tray to the bin or floor waste.
Dry puck: A firm, mostly-dry puck that knocks out as a solid cake.
Dual boiler: A machine with two completely separate boilers — one for brewing, one for steaming — each with its own element and thermostat/PID.

E

E61 Group: The classic Faema E61 brew group — a thermosiphon-fed cast brass group with built-in pre-infusion and a 3-way valve, found on most prosumer HX machines.
E61 group head: A chrome-plated brass brew group originally designed by Faema in 1961, featuring a thermosyphon loop that circulates water from the boiler through the group to keep it at brew temperature. Identified by its distinctive mushroom shape and three-position lever.
Energy rating: An efficiency rating — standby power draw, warm-up time, heat retention.
Error codes: Machine-specific fault codes (e.g., E01, E05, F2) displayed on the screen.
Espresso (short black): A 30–40ml double shot of espresso, served on its own in a demitasse.
Etching: Using a tool (latte art pen, skewer) to draw patterns in the foam surface.
Expansion Valve: Adjustable safety valve that bleeds excess pressure from the boiler back to the inlet, protecting plumbing from thermal expansion.
Extraction yield (EY %): The percentage of the dry coffee mass that ends up dissolved in the cup. Measured by a refractometer.

F

Fast shot: Extraction runs much faster than expected.
Filter basket: The perforated metal cup inside the portafilter that holds the ground coffee. Specified by diameter (49–58mm), dose (7g single, 14–22g double, 20–25g triple), and hole pattern.
Fines: Very small particles (under ~100 microns) produced as a byproduct of grinding.
First crack: The audible popping sound that happens early in roasting, as water escapes bean cell walls.
Flat burr: Two horizontally mounted, parallel-faced burrs that grind coffee between their flat cutting surfaces as beans enter from the centre.
Flat white: A double shot of espresso with 140–160ml of finely textured milk, usually served at 165ml volume. Australian-New Zealand origin, debated between the two.
Float valve: A mechanical valve held shut by a buoyant float. As water drops, the float falls and opens the valve; water rises, the float lifts and shuts it. Common on lever machines and simple boilers.
Flow control device (FCD, flow profiler): A needle-valve mounted in the group head that lets the barista throttle water flow during a shot — enables flow profiling on E61 and lever machines.
Flow profiling: Controlling water flow rate (rather than pressure) during a shot. Pressure becomes a consequence of the flow you dictate and the puck's resistance.
Flow restrictor: Any component (gicleur, orifice, or valve) that restricts water flow into the group, usually to generate gentler pre-infusion.
Flowmeter: Small turbine sensor that counts water passing through it in pulses — used by volumetric machines to dose shots by volume rather than time.
Free pour: Pouring latte art without etching or toppings — using jug movement alone to create patterns.
French press (plunger): An immersion brewer with a metal mesh plunger that separates grounds from coffee.

G

Gasket replacement: Replacing the rubber portafilter gasket — a 10-minute job on most machines.
Gear pump: A continuous-flow positive-displacement pump using meshing gears. Common in larger commercial espresso machines and brewers where smooth, quiet, low-pulsation flow is needed.
GH (general hardness): Total mineral hardness of water, measured in parts per million or German degrees (°dH).
Gicleur: A small brass jet (typically 0.6–0.8 mm) that meters water flow into the group — limits pressure ramp and brew flow.
Gicleur (jet): A small brass jet (typically 0.6–0.8 mm) that meters water flow into the group — limits pressure ramp and brew flow.
Gicleur sizing: Changing the jet inside an E61 group to alter pre-infusion aggressiveness.
Glass carafe / server: A container for decanting brewed coffee — common with pour-overs, Chemex (integrated), and batch brewers.
Gooseneck kettle: A kettle with a long, thin, curved spout that delivers a precise, controllable water stream.
Grate: The slotted top plate on the drip tray that supports cups under the group. Usually stainless steel; on some commercial machines it can be perforated, slatted, or rubber-coated.
Green bean: Unroasted coffee.
Grind by eye: The old-school method of eyeballing the amount of ground coffee in the basket.
Grind by time: An on-demand grinder that runs the motor for a programmed duration (e.g., 6.2 seconds) to deliver a dose.
Grind by weight: An on-demand grinder with an integrated scale under the portafilter cradle, stopping the motor when the target weight is reached.
Grind distribution: The spread of particle sizes in your grind — ideally, most particles are close to the target size (a "tight" distribution).
Grind size: The mean particle diameter of ground coffee, measured in microns (µm) — though most people just refer to "steps" on their grinder.
Grinder burr replacement: Fitting new burrs to your grinder — typically every 500–1000kg of coffee for steel burrs.
Grinder cleaning tablets (Urnex Grindz, Cafiza): Rice-shaped or granular cleaning media that runs through a grinder to absorb oils and flush out fines.
Grinder making metallic screech: High-pitched metal-on-metal sound from the grinder.
Grinder motor hum but no grind: Grinder turns on but burrs don't rotate.
Group brush: A specific shape of brush with an angled head designed to reach the shower screen while the portafilter is removed.
Group cleaner (Cafiza, Puly Caff): An alkaline detergent powder or tablets designed to dissolve coffee oils.
Group Gasket: Rubber seal between the portafilter and the group head — the part that goes hard, leaks, and stops you from locking in straight.
Group gasket (portafilter gasket): Rubber ring sealing the portafilter against the group head — wears flat and leaks; a 6-monthly service item.
Group Head: The brass assembly where the portafilter locks in and brewing happens.
Group head temperature: The actual water temperature delivered to the coffee puck, which is always slightly different from boiler temperature.
Gusher: A shot that runs far too fast — pouring in under 15 seconds at 1:2 ratio, usually from too-coarse grind or a severely channelled puck.

H

Hario Switch: A V60 with a valve, similar concept to the Clever but the V60 shape.
Heart / tulip / rosetta / swan / wave (stacked tulip): Common latte art patterns, listed roughly in order of difficulty.
Heat exchanger (HX): A copper tube running through the steam boiler — brew water flows through it on demand and is heated by surrounding boiler water.
Heating Element: Resistive coil that converts electricity into heat inside the boiler — usually a sheathed nichrome element bolted to the boiler flange.
Heating Element Gasket: Sealing washer between the heating element flange and the boiler — the slow drip behind the panels is almost always this gasket.
Hopper: Bean container mounted on top of the grinder.
Hopper grinding: Loading a large quantity of beans into a hopper and dosing shots on-demand.
Hot water tap: A dedicated outlet (usually operated by a tap or button) that dispenses hot water from the steam boiler for Americanos, teas, or pre-heating cups.
Hybrid (ghost) burrs: A newer burr geometry (pioneered by SSP and Lagom) that combines aspects of both flat and conical designs, often marketed as producing "high clarity" or "sweet" cups.

I

Iced latte: Espresso + cold milk + ice.
Iced long black: A double shot poured over cold water and ice.
Ideal extraction window: The EY range where the coffee tastes balanced — usually 18–22% for espresso and 18–23% for filter.
Immersion vs percolation: Immersion = grounds sit in water for the full brew time (plunger, Clever, AeroPress). Percolation = water flows through grounds in one pass (V60, Chemex, espresso).
IMS screen / competition screen: A precision-etched shower screen (or basket) made by IMS in Italy, with laser-drilled holes and tighter tolerances than stock stamped screens. The "Competition" line is used by most World Barista Championship competitors.
Inconsistent shot times: Same dose, same grind, same machine — different shot times every pull.
Insulation jacket: A foam or foil wrap around the boiler to reduce heat loss.

J

Japanese iced: Pour-over brewing directly over ice, cooling the coffee immediately while preserving its aromatics.

K

Kalita Wave: A flat-bottomed pour-over dripper with three small holes, using a wavy-ridged paper filter.
KH (carbonate / temporary hardness): The portion of hardness made up of bicarbonates (the scale-forming component).
Knob & Handle: Wood, metal, or plastic grips for steam taps and portafilters — wear items that get burned, dropped, and replaced as much for looks as for function.
Knock box: A receptacle (often with a rubber bar) for knocking spent pucks out of the portafilter.
Knock tube: A tall cylindrical version of a knock box, often used on bar tops where width is limited.

L

Latte (café latte): A double shot with 200–240ml steamed milk, served in a glass.
Latte art jug (milk pitcher): The stainless steel jug used to steam and pour milk. Common sizes: 350ml (for 1 drink), 600ml (for 2), 900ml+ (commercial).
Latte art pen: A small tool like a dull skewer used for etching details in latte art.
Leaks from boiler: Water pooling underneath the machine.
Leaks from group: Water escapes around the portafilter during brewing.
Level sensor: Generic term for any device that measures water level — covers conductive autofill probes, capacitive sensors, optical sensors and float-based switches.
Levelling distributor: A spinning tool with angled blades that flattens the grind bed before tamping.
Levelling tool (distribution tool): A spinner or paddle-style tool that rotates on top of the grounds to flatten the bed before tamping.
Lever group: A manually operated brew group where the barista uses a lever to generate extraction pressure, either via a spring (spring-lever) or by pressing directly on the water column (manual piston / dipper).
Line pressure pre-infusion: Using municipal or reservoir water pressure (0.5–3 bar) to gently wet the puck before the main pump kicks in at 9 bar.
Long black: A double shot poured over 120–160ml of hot water. The Australian/NZ alternative to an Americano.
Lungo: A long shot — 1:2.5 to 1:3 ratio, producing a weaker, more voluminous drink.

M

Macchiato (traditional vs Australian): Traditional Italian macchiato = espresso "marked" with a small dollop of foam. Australian macchiato = often a short-sized latte with a small amount of milk, often served in glass.
Melitta: The original pour-over dripper, invented by Melitta Bentz in 1908 — a trapezoid shape with a flat bottom and single hole.
Metal filter: A reusable fine-mesh metal filter.
Microfoam: Milk foam where the bubbles are so small they can't be seen individually — appearing as a glossy, paint-like surface.
Milk fat content: The percentage of fat in milk — full cream (~3.5%), light (~1.5%), skim (<0.5%).
Milk thermometer: An analogue or clip-on thermometer that sits in the milk jug to show steaming temperature.
Mixer tap: A hot water outlet that blends boiler water with fresh cold water on the way out, giving cooler, better-tasting water than raw boiler water.
Mocha: Espresso, steamed milk and chocolate (syrup or powder). In Australia, often served with whipped cream and chocolate powder on top.
Moka pot (stovetop): An aluminium or stainless pressurised brewer invented by Alfonso Bialetti in 1933, producing strong, concentrated coffee on the stovetop.
Motor type (DC vs AC): Grinder motors are either direct current (DC, usually with a control board) or alternating current (AC, simpler, usually 1400 rpm).
Mushroom (E61): The internal brass piston in an E61 group that the cam pushes — controls inlet flow and exhaust to the drip tray.

N

No power: Machine completely dead — no lights, no pump.
No pressure: Pump runs, water flows, but pressure gauge shows nothing or very little.
Not heating: Machine turns on but never gets hot enough to brew or steam.
NSF: An American food-safety and public-health certification body.
Nutation: Tilting the tamper slightly off-vertical during tamping, tracing a small cone to compress the basket edges.

O

O-Rings & Seals: Round rubber seals used throughout the machine — group, valves, taps, fittings. Cheap to stock, instant fix for nine in ten leaks.
Offset (temperature offset): The calibration value entered into a PID to correct for the difference between the sensor reading (usually in the boiler) and actual water temperature at the group.
One-way valve (degassing valve): A small valve in a coffee bag that lets CO₂ escape without letting oxygen in.
OPV (over-pressure valve): Spring-loaded valve that caps brew pressure at a set point (typically 9–10 bar) by venting excess pump output back to the reservoir.
OPV adjustment: Tweaking the over-pressure valve spring preload to change the maximum pump pressure.
Over-extraction: A shot/brew where too much has been extracted, including bitter late-stage compounds. Typically tastes bitter, ashy, hollow, astringent.
Over-pressure: Pump pressure climbs above 12 bar and stays there.

P

Paddle (brew paddle): A lever-style flow control built into the group on machines like the Slayer, Kees van der Westen Speedster and La Marzocco Strada MP.
Palm tamper: A non-handled tamper shaped to sit in the palm and use body weight rather than arm strength.
Paper filter (bleached vs natural): Paper discs, cones or wedges that separate coffee grounds from the brew.
PED (Pressure Equipment Directive): The European Union directive covering pressure vessels like steam boilers.
Pentair / Everpure: Major American water filtration manufacturer (Pentair owns Everpure), popular for commercial food service filtration.
pH: Acidity/alkalinity, 0–14 scale, 7 is neutral.
Piccolo latte: An Australian/NZ invention — an espresso topped up with steamed milk in a 90ml glass. Essentially a smaller, coffee-forward latte.
PID Controller: Electronic temperature controller that holds boiler temp to ±0.5 °C by reading a probe and pulsing the element via a relay or SSR.
PID tuning: The process of setting the P, I and D values in a PID controller to minimise temperature overshoot and settling time for a specific boiler.
Plant milk performance: How well different plant milks behave under steam.
Plumb-in: Connecting an espresso machine directly to mains water (with appropriate filtration and pressure regulation) instead of using the internal reservoir.
Portafilter: Detachable handle that holds the basket and locks into the group head — the part you tamp into and lock up to brew a shot.
Portafilter sneezing: A puff of coffee grounds ejecting from the portafilter when unlocked after a shot.
Portafilter spring (basket retaining clip): The C-shaped wire clip inside the portafilter that grips the basket and stops it falling out when you knock the puck.
Portafilter stand: A cradle or holder that keeps the portafilter level during dosing.
Pour-over: Any method where hot water is poured in a controlled manner over grounds in a filter cone.
Pre-infusion: Low-pressure phase at the start of a shot to wet the puck before full pressure.
Pre-infusion chamber: A small water-filled chamber inside an E61 (and similar) group that fills at line pressure before the pump kicks in, gently wetting the puck before full pressure.
Pre-infusion time: The duration of gentle puck saturation before full extraction pressure.
Precision basket: A filter basket made with laser-drilled or electro-etched holes to tight tolerances (usually ±0.02mm), producing more uniform water flow across the puck.
Pressure Gauge: Analog dial showing pump (brew) pressure or boiler (steam) pressure — your primary diagnostic instrument.
Pressure profiling: Varying the pressure applied to the puck during the extraction — e.g., starting at 2 bar for 10 seconds, ramping to 9 bar, then declining to 6 bar at the end.
Pressure ramp: The speed at which pump pressure rises from zero to full during the start of an extraction.
Pressure Relief Valve (Safety Valve): Spring-loaded boiler safety valve that vents steam if pressure runs away — the last line of defence against a boiler rupture.
Pressurestat: Mechanical pressure switch that turns the heating element on and off to hold the steam boiler at a set pressure — the analogue ancestor of the PID.
Pressurestat (pstat): Mechanical pressure switch that cycles the steam boiler element on and off to hold a set pressure — typically 1.0–1.5 bar.
Pressurised (dual wall) basket: A basket with a second wall and a single pin-hole exit that artificially generates pressure regardless of grind or technique, used on entry-level machines like Breville Bambino and the De'Longhi Dedica.
Primed on-demand: An on-demand grinder that always holds a small amount of coffee in its grind path, dispensing whatever was ground previously and replacing it with a fresh batch.
Probe (Level / Temperature): Stainless rod or thermocouple that tells the controller how full or how hot the boiler is — fouled probes cause overfilling, dry-fires, and runaway PIDs.
Processing (washed, natural, honey): How the coffee cherry is prepared to become green bean. Washed = fruit removed before drying (clean, acidic). Natural = dried with fruit on (fruity, heavier body). Honey = partially fruited (in-between).
Puck preparation: The full sequence of steps between grinding and locking in — dosing, declumping/WDT, distributing, levelling, tamping.
Puck rake: A small manual tool with fingers that reach into the basket to break up clumps before tamping — an alternative to WDT.
Puck screen: A thin metal mesh disc (usually 58mm, 0.2–1.7mm thick) placed on top of the tamped puck.
Pulse pre-infusion: A technique where the pump is switched on and off in bursts at the start of the shot, using the machine's existing plumbing to simulate soft pre-infusion.
Pump expansion valve: A small one-way valve that releases excess pressure created by water expanding as the boiler heats up. Without it, cold-fill water would push past the pump and damage seals.
Pump Head / Brass Pump: The brass body of a rotary pump — contains the rotor, vanes, and bypass valve that build brew pressure on plumbed-in machines.
Pump Motor: AC induction motor that drives a rotary pump head — runs continuously while the pump is engaged.
Pump noise / cavitation: Loud rattling, screaming, or uneven sound from the pump.
Pump pressure vs brew pressure: Pump pressure is what the pump outputs (limited by the OPV); brew pressure is what the puck actually sees, which can be lower due to flow restriction and gicleur effects.
Pump rebuild: Replacing the internal pistons, o-rings or bypass springs on a pump. Standard for rotary pumps after 5–10 years; vibe pumps are usually replaced as a unit.
Pump won't prime: Pump runs but no water reaches the group.
Purge (grinder): Running a small amount of coffee through the grinder to clear residual grounds before dosing fresh beans.

Q

Q Grader: A certified coffee quality evaluator, qualified through a rigorous SCA/CQI exam.

R

RCM / C-Tick: The Regulatory Compliance Mark — Australia and New Zealand's electrical safety and EMC certification, previously called C-Tick.
Refractometer: An optical device that measures the refractive index of a liquid to calculate TDS. VST and Atago are the main brands.
Remineralisation: Adding minerals back to water that has been too heavily filtered (e.g., RO water).
Removable brew group (ZBG): A self-contained brewing unit — used in fully automatic bean-to-cup machines like Jura, Saeco, DeLonghi Magnifica and Miele — that can be slid out for cleaning and descaling.
Reservoir (tank): The removable cold-water tank on a non-plumbed espresso machine. Feeds the pump on demand and includes a low-water sensor so the machine stops before running dry.
Retention: The amount of ground coffee trapped inside the grinder path after a grind cycle.
Reverse osmosis (RO): A filtration method that forces water through a semi-permeable membrane, removing up to 99% of dissolved solids.
Ridged vs ridgeless baskets: Most baskets have a pressed ridge near the top that engages with the portafilter's retaining spring. Ridgeless baskets (used with E61 portafilters fitted with a different spring) sit flush.
Ristretto: A short, concentrated shot — 1:1 to 1:1.5 ratio, typically 18g in, 18–27g out.
Roast date: The date the beans came out of the roaster.
Roast level (light, medium, dark, Italian): How long and hot coffee is roasted. Light = short time (Scandinavian/specialty). Medium = most commercial. Dark = longer (Italian-style). Italian = very dark, oily surface.
Robusta: Coffea canephora — a hardier species with roughly 2× the caffeine of Arabica, more body, heavier crema, and harsher flavour.
Rotary Pump: Quiet, continuous-pressure pump driven by a separate motor — standard on commercial machines and high-end prosumers.
RPM (grinder speed): Revolutions per minute of the burrs. Commercial AC motors run at 1400 rpm; high-end DC motors run at 400–900 rpm.

S

Saturated group: A brew group that is directly attached to (and shares water with) the brew boiler, keeping the group head at a stable, precise temperature at all times.
SCA (Specialty Coffee Association): The global body that sets standards for specialty coffee — brewing, cupping, water quality, barista skills.
SCA certification: Training certifications from the Specialty Coffee Association — Barista Skills, Brewing, Sensory, Roasting and Green Coffee, each at Foundation, Intermediate and Professional levels.
SCA water standards: The Specialty Coffee Association's guidelines for ideal brewing water — target 150 ppm TDS, ~50–80 mg/L calcium carbonate hardness, pH 6.5–7.5.
Scale (timer scale): A coffee scale with an integrated timer — most now Bluetooth-connected to apps.
Scale blockage: Restricted flow or intermittent fault caused by calcium carbonate buildup in boiler, pipes, or solenoid.
Second crack: A later, quieter cracking phase as bean cell walls break down under heat.
Semi-saturated group: A hybrid design where the group is heated by a dedicated element or circulating water from the brew boiler, offering better stability than a basic HX group but at lower cost than a fully saturated group.
Service interval: The recommended frequency for machine and grinder servicing — usually every 12 months for home use, every 3–6 months for cafés.
Shot time (extraction time): The elapsed time from when the pump starts to when you stop the flow at the target yield.
Shot timer: A stopwatch — usually integrated into a scale or a standalone unit — that times espresso extraction.
Shower Screen: Perforated disc at the underside of the group that disperses water evenly across the puck during extraction.
Shower screen replacement: Removing and swapping the shower screen, usually held by a single centre screw.
Sight glass: A clear (usually borosilicate) tube on the side of a steam boiler that shows the current water level at a glance — common on traditional commercial machines.
Single basket / double basket / triple basket: Filter baskets sized for different doses — typically 7–10g (single), 14–22g (double), and 20–25g+ (triple).
Single boiler: A machine with one boiler that is switched between brewing temperature (~93°C) and steaming temperature (~125°C).
Single dosing: Weighing out exactly one shot's worth of beans (e.g., 18g) and loading them into the grinder for each shot — no hopper.
Single origin: Coffee from a single farm, region, or country — bottled without blending.
Siphon (vacuum pot): A two-chamber vacuum brewer where steam forces water up into the grounds chamber, then cools and draws brewed coffee back through a filter.
Slow shot: Extraction runs much slower than expected, or the machine struggles to produce flow.
Solenoid stuck: The 3-way solenoid fails to open (no brew) or fails to close (constant drip, no pressure release).
Solenoid Valve: Electrically operated valve — a coil pulls a steel plunger to open a port, letting water, steam or air pass.
Soupy / watery puck: The puck doesn't knock out as a solid cake — comes out as slurry.
Soupy puck: A wet, sloppy puck that falls out of the basket in chunks rather than a firm disc.
Specialty coffee: Coffee scoring 80+ points on the SCA 100-point scale, produced with attention to quality from farm to cup.
Split jug technique: Pouring from one jug into two cups simultaneously, saving time in busy cafés.
Spout type (standard, sharp/tulip): Different spout profiles — wide standard spouts for big pours, sharp/tulip spouts for precision latte art.
Spouted portafilter: A portafilter fitted with one or two spouts that split the espresso flow. Single-spout versions (single-dose) are for one cup, double-spout for two.
Spritzing: Visible fine droplets shooting sideways out of a bottomless portafilter during extraction — a symptom of channelling.
Spurting / geysering: Water erupting from the shower screen or brew path, often with a gurgling sound.
Steam boiler: The larger boiler that produces steam for milk texturing and hot water for tea — typically held at 120–130 °C and 1.0–1.5 bar.
Steam tip: The removable nozzle at the end of the steam wand with 1–6 holes drilled at specific diameters and angles.
Steam Wand: Articulating tube that delivers dry steam for milk texturing.
Steam wand blocked: Little to no steam flow, or uneven spray from the tip.
Steam wand purge: Running steam through the wand briefly after each steaming session to clear residual milk from the tip.
Steaming: Injecting steam into milk to heat it.
Stepless (micrometric) adjustment: A grind adjustment that varies continuously with no fixed increments.
Stepped adjustment: A grind adjustment system with fixed increments (clicks) — e.g., 40 steps between espresso and filter.
Stretching: The first phase of steaming, where the wand tip is held near the milk's surface to draw air in, creating foam.
Switch (Power, Brew, Steam): Mechanical rocker or push-switch on the front panel — handles the on/off, brew, and steam selections. They wear out after a few hundred thousand cycles.

T

Tamp pressure: The force applied to the tamper when compressing the puck. Historically cited as ~30lb, but now understood to matter much less than uniformity.
Tamper: Tool used to compress the coffee puck evenly in the basket before brewing.
Tamper fit (58mm, 58.35mm, convex vs flat): The diameter and shape of the tamper base relative to the basket inner diameter.
Tamping: Compressing the grounds in the basket with a tamper, producing a flat, uniformly dense puck.
Tamping mat: A rubber or silicone mat that cushions the portafilter during tamping and prevents bench damage.
Tap / Steam Valve Assembly: The whole knob, stem, seal and seat assembly behind a steam or hot-water tap — drips and stiff knobs come from worn seats and o-rings inside.
TDS (total dissolved solids): The percentage of the brewed liquid that is dissolved coffee (vs water). Measured by refractometer.
TDS (water): Total dissolved solids in water, measured in parts per million.
Temperature stability: The consistency of brew water temperature within a shot and across back-to-back shots.
Texturing: The second phase of steaming, where the wand is buried deeper and the milk is vortexed to break up big bubbles into silky microfoam.
Thermal fuse: A safety device that permanently breaks the circuit if the boiler overheats (e.g., from a failed thermostat or dry-boil condition).
Thermoblock: A small aluminium or stainless steel block with a water channel and a heating element that heats water on-demand, millilitres at a time.
Thermocoil: Breville's proprietary thermoblock design — a stainless steel coil wrapped around a heating element, giving better temperature control than a basic thermoblock while still being fast to heat up.
Thermostat: Mechanical bimetallic switch that opens or closes a circuit at a set temperature — used for boiler control on simpler machines and as a safety cutout on all machines.
Third wave: The movement (started in the 2000s) treating coffee as a craft product like wine, with emphasis on origin, variety, roast, and brew method.
Three-way solenoid dripping: A slow drip from the group after a shot ends, indicating the solenoid isn't sealing properly.
Tubing & Hose (PTFE / Silicone / Braided): Internal water and steam lines — PTFE for high-temperature brew water, silicone for low-pressure cold lines, braided stainless for plumbed inlets.
Turkish (cezve): Very finely ground coffee boiled with water (and often sugar) in a small long-handled pot, served unfiltered.

U

Under-extraction: A shot/brew where too little of the soluble material has been extracted. Typically tastes sour, thin, grassy, salty.
Unimodal vs bimodal distribution: Unimodal distribution has one peak (most particles at one size). Bimodal has two peaks (lots of fines AND lots of target-size particles).

V

V60: A conical pour-over dripper invented by Hario, with spiral ridges and a single large hole at the bottom.
Vacuum breaker stuck: The small valve that vents boiler air on startup fails to close, causing continuous steam escape from the top of the boiler.
Varietal: The specific genetic variety of Arabica — e.g., Bourbon, Typica, Geisha (Gesha), SL28, SL34, Pacamara, Caturra, Catuai.
Vibration Pump: Compact, inexpensive electromagnetic pump that pulses water at 50 Hz — standard on home and entry-level machines.
VST: The company founded by Vince Fedele that makes the industry-standard refractometer, laser-etched baskets, and ExtractMojo software.

W

Wand & Tip: The pipe and removable tip nozzle that delivers steam to the milk jug — tip hole count and size define how the wand handles different volumes.
WaterMark: The Australian regulatory certification (administered by the ABCB) for plumbing products connecting to drinking water systems.
WaterMark certification: The Australian mandatory certification for plumbing products that come into contact with drinking water.
WDT (Weiss Distribution Technique): Using a thin tool (needle, acupuncture needle) to stir the grounds in the basket before tamping, breaking up clumps and redistributing density.
WDT tool: A handle holding 4–8 fine needles (acupuncture needles, 0.3–0.4mm) used to stir the grounds in the basket.
Weak steam: Steam pressure feels anaemic — foam is slow or impossible to build.
World Barista Championship (WBC): The global annual barista competition where competitors present one of each — espresso, milk drink, signature drink — scored by sensory judges.
Worm gear adjustment: A fine, high-resolution grind adjustment mechanism using a worm-and-gear drive — used on precision grinders like the Weber Key.

Y

Yield (weight out): The mass of liquid espresso produced by the shot, measured in grams (not millilitres).

Z

Zero point: The grind setting at which the burrs just barely touch (make contact without coffee).