Glossary of Brewing Terms

A plain-language reference for the terms that turn up across these guides, in club recipes and on brew days. Grouped by area, alphabetical within each group.

Where a term names something the club has a page for — a malt, a hop, a yeast, a style — it links straight there, so you can go from “what is a crystal malt” to the actual specs of the one in your recipe. The brew-day walkthrough is where most of these appear 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, and the tube reaching to the keg floor. See Kegging & Carbonation.
• Conical / FermZilla / All Rounder — fermenters with a cone or pressure kit allowing yeast harvesting and 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.
• Hydrometer — a weighted float measuring the density of wort or beer. See Reading Gravity, ABV & Efficiency.
• Recirculation arm — the return that pumps wort from the bottom of an all-in-one back over the top of the grain bed.
• Refractometer — reads sugar (°Brix) from two drops; ideal pre-fermentation, needs correcting once alcohol is present.
• RAPT Pill / tilt — a floating wireless sensor logging gravity and temperature through a sealed fermenter.
• Spunding valve — an adjustable pressure-relief valve holding a target pressure during pressure fermentation.

Hot side — mash and boil

• Boil-over — wort foaming over the kettle, usually at the hot break.
• 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.
• Dough-in / mash-in — stirring the crushed grain into the strike water.
• DMS (dimethyl sulfide) — cooked corn or creamed sweetcorn. Formed from SMM in the malt by heat, and driven off by a vigorous uncovered boil. A process fault with no fermentation fix. Pilsner malt carries much more SMM, which is why pilsner beers want a 90-minute boil — and why slow chilling can undo one.
• 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.
• Kettle finings — clarifiers added late in the boil (Whirlfloc, Irish moss) that help proteins clump and drop out.
• Lauter — separating sweet wort from the spent grain: draining plus 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. See Brewing Water Basics, and acidulated malt for the easiest lever.
• Recirculation — gently pumping wort over the grain bed to set a clear filter and even the temperature; too fast compacts the bed and gives a 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 temperature.
• Trub — the sediment of coagulated protein and hop matter left after the boil.
• Whirlpool / hop stand — holding hot (≈75–80 °C) wort after the boil with late hops for aroma. See Dry Hopping & Whirlpool.

Water and minerals

• Alkalinity / bicarbonate (HCO₃⁻) — water’s buffering capacity; raises mash pH.
• Calcium chloride (CaCl₂) — adds calcium and chloride; rounds out malt character.
• Campden (metabisulphite) — a tablet that neutralises chlorine and chloramine in brewing water. One crushed tablet per 75 L, in all of it.
• Chloramine / chlorophenol — chloramine is a tap-water disinfectant; if not removed it makes chlorophenols, the plaster and TCP fault. See Bandaid, TCP & Clove.
• Gypsum (CaSO₄) — adds calcium and sulfate; sharpens hop bitterness.
• ppm (parts per million) — the unit for mineral 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 is crisp and bitter, low is soft and malty. See Brewing Water Basics.

Measurements and numbers

All of these are covered properly in Reading Gravity, ABV & Efficiency.

• ABV (alcohol by volume) — strength; ≈ (OG − FG) × 131.25.
• Attenuation (apparent) — how much gravity the yeast removed: (OG − FG)/(OG − 1). How dry it finished.
• EBC / SRM — colour scales (EBC ≈ 2 × SRM); higher is darker.
• Efficiency — how much of the grain’s sugar you extracted. Conversion (mash only), mash/lauter (including sparge), brewhouse (whole system into the fermenter, typically 65–80%).
• FAN (free amino nitrogen) — the pool of yeast-usable nitrogen in wort, largely set in the mash. Yeast builds its amino acids from it; run short and it makes its own, which is where diacetyl and sulfur off-flavours come from. Low on high-adjunct grists. Also affects thiol release. See Yeast Handling.
• H₂S / SO₂ — the two sulfur faults, at opposite ends of the same problem. Rotten egg (H₂S) is the sulfate-reduction pathway backing up for want of FAN; struck match (SO₂) is the other end. Both are biological, and both respond to getting aeration and nutrition right.
• 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

• Acetaldehyde — green apple, solvent, fresh-cut pumpkin. A normal intermediate on the way to ethanol; it lingers when the yeast is under-aerated or short of zinc, because the enzyme that finishes the job cannot keep up. Biological — warm, healthy yeast clears it.
• Autolysis — yeast breaking down after long contact, giving rubbery, meaty or savoury off-flavours and damaged head retention. The reason not to leave beer on the yeast cake for weeks after FG.
• Biological vs process fault — the first question to ask about any off-flavour. Biological faults (diacetyl, acetaldehyde, H₂S) are made by yeast and need living, warm, healthy yeast to clear them, so the window closes the moment you crash. Process faults (DMS, oxidation, chlorophenol) come from ingredients, equipment or technique, and no amount of conditioning fixes them — only prevention. Getting this backwards sends you after the wrong thing entirely.
• 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. A one-way door — see Diacetyl before you do it.
• Step crash — dropping to crash temperature in stages rather than all at once. Avoids cold-shocking the yeast’s flocculation machinery, and gives haze particles time to form dense settleable aggregates instead of loose micro-gels. Slow crashes clear better than fast ones.
• Diacetyl (VDK) — the buttery, butterscotch fault. Cleaned up by a warm diacetyl rest — which is misnamed, because it is about giving the chemistry time, not the yeast.
• Esters — fruity aroma compounds from yeast; encouraged warm, suppressed cool or under pressure. Central to Belgian styles.
• Flocculation — how readily yeast clumps and settles out. High flocculators like WLP002 and S-04 clear fast but can drop out before they have finished cleaning up.
• Forced diacetyl test — heating a sample to 60 °C for 20 minutes to convert precursor, so you can smell what the beer will become. The only reliable pre-crash check.
• Fusel alcohols — harsh, hot, solventy higher alcohols from hot or stressed fermentation. Frequently misdiagnosed as phenolic.
• 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. A long one makes more diacetyl precursor.
• Phenols — clove, smoky or medicinal compounds; desirable in some Belgians and wheat beers, a fault otherwise. See Bandaid, TCP & Clove.
• Pitching / pitch rate — adding yeast; dry yeast ≈ 0.5–1.0 g/L, weighed. See Yeast Handling.
• POF (phenolic off-flavour positive) — a yeast’s genetic ability to make 4-vinylguaiacol, the clove phenol. It is a yes/no switch, not a scale: it is why Munich Classic makes clove and US-05 cannot at any temperature.
• Repitching / slurry — reusing harvested yeast from a prior batch.
• Spunding — sealing the fermenter to trap CO₂ and carbonate the beer naturally.
• Zinc — trace mineral and cofactor for alcohol dehydrogenase, the enzyme that finishes turning acetaldehyde into ethanol. The one nutrient homebrewers reliably run short of; brewing salts do not supply it, yeast nutrient blends do.

Hops and aroma

Every hop the club has brewed with has a page under hops with its own alpha and oil figures.

• Alpha / beta acids — hop resins; alpha acids isomerise in the boil to make bitterness. High-alpha bittering hops like Magnum exist for this job alone.
• Biotransformation — yeast converting hop compounds into new aromas when dry-hopped during active fermentation. See Dry Hopping & Whirlpool.
• Cohumulone — an alpha-acid fraction; higher levels are associated with harsher bitterness.
• Dip hopping — steeping hops in hot water, then adding to the fermenter at pitch.
• Dry hopping — adding hops without heat, during or after fermentation, for aroma.
• First wort hopping — adding hops to the kettle during lautering, before the boil.
• Hop burn — harsh, gritty harshness from very heavy or very fresh dry hopping.
• Hop creep — renewed fermentation from enzymes in dry hops, lowering FG, raising carbonation and restarting the diacetyl clock. See Diacetyl — this is a bottling safety issue as much as a flavour one.
• Humulinones — oxidised alpha acids from dry hops; about two-thirds 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. Terpenes give floral and citrus character; thiols give the tropical and passionfruit notes that NZ hops like Nelson Sauvin and Nectaron are prized for, and yeast can release or transform them.
• Total oil — the volume of aromatic oils in a hop (mL/100 g); higher means 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 from the bottom and stops when lifted.
• Carbonation drops — pre-measured priming sugar, about 2 per 750 mL bottle.
• Counter-pressure / closed bottling — filling bottles under CO₂ to limit oxygen. The way to get competition bottles off a keg — see Kegging, Carbonation & Competition Bottles.
• Force carbonation — carbonating a keg with CO₂ under pressure.
• Headspace — the air or CO₂ gap at the top of a bottle or keg.
• Priming sugar — the measured sugar dose that carbonates bottle-conditioned beer. Calculated assuming no further fermentation, which is why hop creep matters.
• Volumes CO₂ — the carbonation unit; ales ≈ 2.4–2.6.

Wild, sour and barrel

Context for all of these is in Wild, Sour & Barrel-Aged Beer.

• Acetobacter — oxygen-loving bacteria making acetic acid (vinegar); the enemy of a barrel with too much air in it.
• 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 its activity.
• Foeder — a large wooden fermenting and aging vessel for sour and wild beer.
• K-meta (potassium metabisulphite) — sulphite used to sanitise barrels and oak. StarSan and iodophor must never be used on wood.
• Kettle sour — souring wort with Lactobacillus before the boil for a quick, clean sour that never touches your clean gear.
• Lactobacillus / Pediococcus — souring bacteria producing lactic acid. Pedio is slower and causes the sick phase.
• Mixed culture — a blend of Sacch, Brett and bacteria fermenting together.
• Pellicle — the film that can form on a wild beer’s surface; a sign of microbial activity, not spoilage.
• Sick phase — a normal, temporary blue-cheese and buttery stage in Pedio fermentations that Brett later cleans up.
• Solera — an aging system where only part of a vessel is drawn off and it is topped up with fresh beer, so the culture runs continuously and every draw is a blend of vintages. The club’s 250 L Flanders red barrel works this way.
• Toast level (oak) — how heavily oak is toasted; light gives coconut, vanilla and lactones, heavier gives spice and smoke.

Ingredients and styles

Every malt, hop and yeast in a club recipe has a page with its own specs — browse fermentables, hops and yeast.

• Adjunct — a non-barley fermentable or addition: wheat, oats, flaked barley, sugar, rice, corn.
• Base malt — the bulk, enzyme-rich malt providing most of the fermentable sugar, usually 70–100% of the grist. Gladfield Ale, Pilsner and Maris Otter are the common ones here.
• BJCP — the Beer Judge Certification Program, whose guidelines define the style categories used by Euroclash and most competitions we enter.
• Crystal / caramel malt — kilned specialty malt adding colour, sweetness and body, from light through medium to dark.
• Diastatic power — a malt’s enzyme strength for converting starch, including any adjunct starch. Base malts carry it; specialty malts largely do not, which sets how much adjunct a grist can support.
• Lovibond (°L) — a malt colour scale, close to SRM.
• Specialty malt — roasted or kilned malts added for colour and flavour rather than bulk sugar: chocolate, roast barley, Munich, Special B.