Glossary of Brewing Terms

A plain-language reference for the terms that show up across these guides and the brew logs. Grouped by area; alphabetical within each group. Many terms have a fuller treatment in the guide for that area — the brew-day walkthrough is the place to see most of them in context.

Equipment

• All-in-one (electric brewery) — a single vessel that mashes, sparges, and boils with a built-in element and pump (BrewZilla, Grainfather, Anvil Foundry).
• Airlock / bubbler — a one-way valve (with a little sanitiser in it) that lets fermentation CO₂ out while keeping air and bugs out.
• Ball lock / diptube — the keg’s gas and liquid connectors (ball lock) and the tube reaching to the keg floor (diptube) used for filling and serving.
• Conical / FermZilla / All Rounder — fermenters with a cone or pressure kit that allow yeast harvesting and/or pressure fermentation.
• Corny (cornelius) keg — a ~19 L reusable stainless keg, the homebrew standard.
• False bottom / grain basket / malt pipe — the perforated screen or removable basket that holds the grain bed and lets wort drain clear of the grain.
• Hydrometer — a weighted float that measures gravity (density) of wort or beer.
• Recirculation arm — the return that pumps wort from the bottom of an all-in-one back over the top of the grain bed during the mash.
• Refractometer — reads sugar (°Brix) from two drops; ideal pre-fermentation.
• RAPT Pill / tilt — a floating wireless sensor that logs gravity and temperature through a sealed fermenter.
• Spunding valve — an adjustable pressure-relief valve used to hold a target pressure during pressure fermentation.

Hot side — mash and boil

• Boil-over — wort foaming over the kettle, usually at the hot break; prevented by breaking the foam.
• Conversion — the mash step where enzymes turn grain starch into fermentable sugar.
• Dough ball — a clump of dry flour trapped in grain at mash-in that never converts; break them up.
• Dough-in / mash-in — stirring the crushed grain into the strike water.
• DMS (dimethyl sulfide) — a cooked-corn off-flavour driven off by boiling uncovered.
• Grain bed — the settled mass of grain that also acts as a filter during lautering.
• Hot break — the fast protein foam that rises as wort reaches the boil; the boil-over moment.
• Kettle finings — clarifiers added late in the boil (e.g. Whirlfloc, Irish moss) that help proteins clump and drop out.
• Lauter — separating the sweet wort from the spent grain (draining + sparging).
• Mash — steeping crushed grain in hot water (~65–67 °C) to convert starch to sugar.
• Mash out — raising the mash to ~75–78 °C to stop enzyme activity and thin the wort.
• Mash pH — the acidity of the mash; 5.2–5.4 is the target band for pale ales.
• Recirculation — gently pumping wort over the grain bed to set a clear filter and even temperature; too fast compacts the bed (stuck mash).
• Sparge — rinsing residual sugar from the grain with hot water. Fly = continuous slow rinse; batch = add, drain, repeat; no-sparge = full volume in the mash.
• Strike water — the mash water, heated so that adding grain lands at mash temp.
• Trub — the sediment of coagulated protein and hop matter left after the boil/whirlpool.
• Whirlpool / hop stand — holding hot (≈75–80 °C) wort after the boil with late hops for aroma, while spinning trub into a cone.

Water and minerals

• Alkalinity / bicarbonate (HCO₃⁻) — water’s buffering capacity; raises mash pH.
• Calcium chloride (CaCl₂) — salt that adds calcium + chloride; rounds out malt.
• Campden (metabisulphite) — a tablet/powder that neutralises chlorine and chloramine in brewing water.
• Chloramine / chlorophenol — chloramine is a tap-water disinfectant; if not removed it makes chlorophenols (plaster/band-aid off-flavour).
• Gypsum (CaSO₄) — salt that adds calcium + sulfate; sharpens hop bitterness.
• ppm (parts per million) — the unit for mineral (ion) concentrations in water.
• RO water — reverse-osmosis water; a near-blank slate to build a profile on.
• Sulfate:chloride ratio — the main flavour lever: high = crisp/bitter, low = soft/malty.

Measurements and numbers

• ABV (alcohol by volume) — strength; ≈ (OG − FG) × 131.25.
• Attenuation (apparent) — how much gravity the yeast removed: (OG − FG)/(OG − 1); i.e. how dry it finished.
• EBC / SRM — colour scales (EBC ≈ 2 × SRM); higher = darker.
• Efficiency — how much of the grain’s sugar you extracted. Conversion (mash only), mash/lauter (incl. sparge), brewhouse (whole system into fermenter, typically 65–80 %).
• FAN (free amino nitrogen) — yeast-available nitrogen in wort; affects health and thiol release.
• FG (final gravity) — gravity once fermentation is complete.
• Gravity points — the digits after the decimal × 1000 (1.050 = 50 points).
• IBU (international bitterness unit) — measured bitterness; ~1 mg/L iso-alpha-acid.
• OG (original gravity) — gravity of the wort going into the fermenter.
• Plato / Brix (°P, °Bx) — sugar-by-weight scales; ~4 points SG ≈ 1 °P.
• PPG / extract potential — sugar a grain can yield; base malt ≈ 300 points·L/kg.
• Specific gravity (SG) — density relative to water (1.000).

Fermentation and yeast

• Autolysis — yeast breaking down after long contact, giving rubbery/savoury off-flavours.
• Closed transfer — moving beer between vessels under CO₂ with no air contact.
• Cold crash — chilling finished beer to ~1–4 °C to drop yeast and haze before packaging.
• Diacetyl (VDK) — a buttery off-flavour; cleaned up by a warm diacetyl rest at the end of fermentation.
• Esters — fruity aroma compounds from yeast; encouraged warm, suppressed cool or under pressure.
• Flocculation — how readily yeast clumps and settles out.
• Fusel alcohols — harsh, hot, solventy higher alcohols from hot/stressed fermentation.
• Generation — how many times a harvested yeast has been repitched (gen 1 = fresh).
• Krausen — the foamy head on top of actively fermenting beer.
• Lag phase — the quiet 12–24 h after pitching before visible fermentation.
• Phenols — clove/smoky/medicinal compounds; desirable in some Belgians, a fault (chlorophenol) otherwise.
• Pitching / pitch rate — adding yeast; dry yeast ≈ 0.5–1.0 g/L (weigh it).
• Repitching / slurry — reusing harvested yeast (the slurry) from a prior batch.
• Spunding — sealing the fermenter to trap CO₂ and carbonate the beer naturally.

Hops and aroma

• Alpha / beta acids — hop resins; alpha acids isomerise in the boil to make bitterness.
• Biotransformation — yeast converting hop compounds (thiols, terpenes) into new aromas when dry-hopped during active fermentation.
• Cohumulone — an alpha-acid fraction; higher levels are associated with a harsher bitterness.
• Dip hopping — steeping hops in hot water then adding to the fermenter at pitch.
• Dry hopping — adding hops without heat, during/after fermentation, for aroma.
• First wort hopping — adding hops to the kettle during lautering, before the boil.
• Hop burn — harsh, gritty hop harshness from very heavy/fresh dry hopping.
• Hop creep — renewed fermentation from enzymes in dry hops, lowering FG and raising carbonation.
• Humulinones — oxidised alpha acids from dry hops; ~⅔ as bitter as iso-acids, but smoother.
• Iso-alpha-acids — the bitterness compounds formed when alpha acids isomerise in the boil.
• Keg hopping — leaving dry hops in the serving keg to boost and hold aroma.
• Terpenes / thiols — hop aroma compounds (floral/citrus terpenes; tropical-fruit thiols) that yeast can release or transform.
• Total oil — the volume of aromatic oils in a hop (mL/100 g); higher = more aroma potential.

Packaging and carbonation

• Bottle conditioning — carbonating in the sealed bottle by feeding yeast priming sugar.
• Bottling wand — a spring-tip tube that fills bottles from the bottom and stops when lifted.
• Carbonation drops — pre-measured priming sugar (≈2 per 750 mL bottle).
• Counter-pressure / closed bottling — filling bottles under CO₂ to limit oxygen.
• Force carbonation — carbonating a keg with CO₂ under pressure (fast or slow).
• Headspace — the air/CO₂ gap left at the top of a bottle or keg.
• Priming sugar — the measured sugar dose that carbonates bottle-conditioned beer.
• Volumes CO₂ — the carbonation unit (litres of CO₂ per litre of beer); ales ≈ 2.4–2.6.

Wild, sour and barrel

• Acetobacter — oxygen-loving bacteria that make acetic acid (vinegar); the enemy of barrels with too much air.
• Angel’s share — beer lost to evaporation through barrel staves during aging.
• Brettanomyces (Brett) — a wild yeast giving funk, dryness, and complexity over time.
• Cellobiose — a sugar from toasted oak that Brett can ferment, extending activity.
• Foeder — a large wooden fermenting/aging vessel for sour and wild beer.
• K-meta (potassium metabisulphite) — sulphite used to sanitise barrels and oak without harsh chemicals.
• Kettle sour — souring wort with Lactobacillus before the boil for a quick clean sour.
• Lactobacillus / Pediococcus — souring bacteria (lactic acid); Pedio is slower and causes the “sick phase.”
• Mixed culture — a blend of Sacch + Brett + bacteria fermenting together.
• Pellicle — the protective film that can form on a wild/sour beer’s surface; a sign of microbial activity, not spoilage.
• Sick phase — a normal, temporary blue-cheese/buttery stage in Pedio fermentations that Brett later cleans up.
• Toast level (oak) — how heavily oak is toasted; light = coconut/vanilla/lactones, heavier = spice/smoke.

Ingredients and styles

• Adjunct — a non-barley fermentable or addition (wheat, oats, sugar, rice, corn).
• Base malt — the bulk, enzyme-rich malt that provides most fermentable sugar.
• BJCP — the Beer Judge Certification Program, whose style guidelines define categories.
• Crystal / caramel malt — kilned specialty malt adding colour, sweetness, and body.
• Diastatic power — a malt’s enzyme strength for converting starch (and any adjunct starch).
• Lovibond (°L) — a malt colour scale (close to SRM).
• Specialty malt — roasted or kilned malts added for colour and flavour, not bulk sugar.