Glossary
30 terms you'll run into on spec sheets, listings and in our guides.
B
- Backflushing
- Cleaning group paths with a blind basket on machines that support it.
- Bloom
- Initial wetting of grounds that releases trapped CO₂.
- Burr
- Grinding surface; two burrs crush beans at a set gap.
C
- Channeling
- Water finds weak paths through an espresso puck, causing uneven extraction.
- Crema
- Emulsified oils and gas on espresso; not a quality score by itself.
D
- Descaling
- Removing mineral scale from boilers and heaters with approved solution.
- Distribution
- Spreading grounds evenly in a portafilter before tamping.
- Dose
- Mass of dry coffee used for a brew, usually in grams.
- Dual boiler
- Separate boilers for brewing and steaming.
E
- Extraction
- Dissolving flavor compounds from grounds into water.
F
- Fines
- Very small particles that extract quickly and can muddy a cup.
G
- Golden Cup
- Historical brewing-chart framework linking strength and extraction, not a universal recipe.
- Gooseneck
- Narrow kettle spout for controlled pouring.
H
- Heat exchanger
- Steam boiler that heats brew water through a tube (HX).
M
- Moka pot
- Stove-top pot that pushes water through coffee with steam pressure.
O
- Over-extraction
- Too much extracted; tastes bitter or harsh.
P
- PID
- Controller that holds boiler temperature near a setpoint.
- Portafilter
- Handle and basket that hold espresso grounds.
- Puck
- Compressed cake of espresso grounds after tamping.
R
- Ratio
- Coffee-to-water (or dose-to-yield) relationship by weight.
- Retention
- Grounds left inside a grinder after use.
S
- SCA
- Specialty Coffee Association — publishes coffee standards and programs.
- Single-dose
- Grinding only the beans for one brew to cut hopper staling and retention.
- Siphon
- Vacuum pot that moves water with vapor pressure, then draws coffee down.
- Super-automatic
- Bean-to-cup machine that grinds, doses and brews at a button.
T
- TDS
- Total dissolved solids — a lab measure of brew strength.
- Thermoblock
- Fast-heating metal block that warms brew water on demand.
U
- Under-extraction
- Too little extracted; tastes sour or thin.
W
- Water hardness
- Mineral content that affects taste and machine scale.
Y
- Yield
- Mass of liquid espresso in the cup.