The key terms you will run into when brewing beer, explained in 2 to 4 sentences. From OG and IBU to diacetyl rest and whirlpool.
67 entries
Acidulated malt is Pilsner malt that has been fermented with lactic acid bacteria and then dried. It carries about 2 to 4 % lactic acid and lowers mash pH without using brewing salts or food acid. Typical dosage is 1 to 5 % of the grist, especially in very pale beers brewed with soft water.
Related terms: Mash pH, Brewing Water
An airlock is a water-filled valve on the fermenter that lets CO2 escape without letting oxygen or insects into the beer. Active fermentation shows as regular bubbling. With very active ferments or high-krausen NEIPA, it is often replaced by a blow-off tube into a jar of sanitiser.
Related terms: Fermenter, Primary Fermentation
Alcohol By Volume (ABV) is the percentage of alcohol in finished beer, derived from the difference between Original Gravity and Final Gravity. A common approximation is ABV (%) = (OG, FG) × 131.25 with OG and FG as specific gravity values. Typical homebrew styles land between 4 and 7 %, while imperial stouts or doppelbocks can reach 8 to 12 %.
Related terms: Original Gravity (OG), Final Gravity (FG)
Alpha acids (humulones) are the main bittering compounds in hops, expressed as a percentage by weight (e.g. Magnum 14 %, Saaz 3 %). During the boil they isomerise into iso-alpha acids, which taste bitter in finished beer. The IBU value is derived from alpha content, hop mass and boil time.
Related terms: Hops, International Bitterness Units (IBU),
Apparent attenuation describes the percentage of original extract converted to alcohol and CO2: AA (%) = (OG, FG) / OG × 100 with both in Plato. Most ale yeasts reach 70 to 80 %, some Saison strains exceed 90 %. A low attenuation often points to a stuck fermentation or fermentation temperatures that were too cold.
Related terms: Original Gravity (OG), Final Gravity (FG), Diacetyl Rest
BIAB (Brew in a Bag) means mashing in a fine mesh bag inside a single brew kettle. After the mash the bag with the spent grain is lifted out, drained and optionally sparged, and the boil happens in the same pot. BIAB saves equipment and space but has slightly lower brewhouse efficiency than a classic lauter tun.
Related terms: Mashing, Lautering, Brewhouse Efficiency
During the boil the wort is held at a rolling boil for 60 to 90 minutes to coagulate proteins, sanitise the wort, drive off unwanted volatiles (DMS) and isomerise hop bitterness. Evaporation should sit around 6 to 10 % per hour. With Pilsner malt a longer boil is recommended to reduce DMS.
Related terms: Hop Addition, Whirlpool, International Bitterness Units (IBU)
A bottle filler is a rigid tube with a spring-loaded tip that opens when pressed against the bottom of a bottle, filling it from the bottom up with minimal oxygen pickup. This reduces foaming and oxidation compared to free pouring. It is typically connected to a tap on the fermenter or a bottling bucket.
Related terms: Secondary / Bottle Conditioning, Carbonation
Bottom-fermenting yeast (Saccharomyces pastorianus) ferments cold at 8 to 14 °C and settles at the bottom of the fermenter. It produces a very clean, malt-driven flavour with little ester character but needs 2 to 6 weeks of cold storage. Pilsner, Helles, Märzen, Bock and Schwarzbier are classic bottom-fermented styles.
Related terms: Top-Fermenting (Ale), Yeast,
The brew kettle is the main vessel for heating, mashing (in BIAB) and boiling the wort. Homebrewers typically use 30 to 70 L stainless pots with hotplates, gas burners or built-in induction. A thick bottom prevents scorching; a ball valve and thermometer are very useful.
Related terms: BIAB (Brew in a Bag), Boiling the Wort
Brewhouse efficiency tells you how much of the theoretical malt extract ends up in the kettle wort, expressed as a percentage or l·°P / kg. BIAB homebrewers usually hit 60 to 70 %, professional systems with a lauter tun reach 75 to 80 %. A stable efficiency is essential for designing reproducible recipes.
Related terms: Original Gravity (OG), Extract Yield, BIAB (Brew in a Bag)
Brewing water shapes mash pH and flavour through its mineral profile (calcium, magnesium, sulfate, chloride, bicarbonate). Calcium (50 to 150 mg/L) stabilises fermentation, sulfate accentuates hop bitterness, and chloride supports malt body. Hard, bicarbonate-rich water suits dark beers, while soft water fits pale Pilsners or NEIPA.
Related terms: Mash pH, Acidulated Malt
The BU:GU ratio relates IBU to gravity units (e.g. OG 1.050 = 50 GU). Values under 0.5 read malt-forward, 0.5 to 0.7 balanced, and 0.8 and above clearly hop-forward. It is a quick sanity check during recipe design to see whether bitterness and body fit each other.
Related terms: International Bitterness Units (IBU), Original Gravity (OG)
Carbonation describes the CO2 content of the finished beer, usually in volumes of CO2 or g/L (1 vol = 1.96 g/L). Pilsner and wheat beer sit at 4.5 to 5.5 g/L (2.3 to 2.8 vol), stout commonly lower at 3.5 to 4 g/L. Homebrewers control it through speise, table sugar priming or forced carbonation in a keg.
Related terms: Speise (Reserved Wort), Spunding, Secondary / Bottle Conditioning
A cold crash means cooling fully fermented beer to 0 to 4 °C for 24 to 48 hours so that yeast, hop debris and proteins drop out faster. The result is a clearer beer with less sediment at packaging. Non-pressure-rated fermenters can suck airlock liquid or oxygen back into the beer due to vacuum (suckback).
Related terms: Conditioning / Maturation,
Conditioning is the time after fermentation in which flavours round out, esters integrate and haze settles. Hop-driven beers like NEIPA condition briefly (3 to 7 days), lagers condition for a long time (4 to 12 weeks cold). It is not the same as secondary fermentation and often runs in parallel or right after.
Related terms: Secondary / Bottle Conditioning, Cold Crash
Crystal or caramel malt is produced by stewing the still-moist grain so that the starches turn into a sugary solution inside the husk before being kilned to crystallised sugars. The result is residual sweetness, body and caramel flavour, ranging from very light Caramel Pils (10 EBC) to deep Cara Aroma (350 EBC). Typical use is 3 to 15 % of the grist.
Related terms: Malt, EBC Colour
Diacetyl is a fermentation by-product that tastes of butter, caramel or popcorn and is undesirable in most beer styles. It is produced early during fermentation and is normally reabsorbed by the yeast. If beer is racked off the yeast too early or chilled too soon, it can remain.
Related terms: Diacetyl Rest, Yeast
A diacetyl rest is a warm phase at the end of primary fermentation (ales 20 to 22 °C, lagers 16 to 18 °C, each 2 to 4 days) during which yeast reduces diacetyl back to neutral compounds. It is especially important for lager yeast, because at cold lagering temperatures diacetyl breaks down very slowly. Only after the rest is the beer cooled down for lagering.
Related terms: Diacetyl, Bottom-Fermenting (Lager)
Dry hopping means adding hop pellets or cones cold to the beer during or after fermentation to extract intense aroma without additional bitterness. Typical dosage is 2 to 8 g/L for IPA and NEIPA, with contact times of 2 to 5 days. NEIPA dry hops often go in during active fermentation to use biotransformation.
Related terms: Hops, NEIPA (Hazy IPA), IPA (India Pale Ale)
Dry yeast (e.g. Fermentis S-04, US-05, W-34/70) is inexpensive, has a long shelf life and contains enough cells for a standard gravity batch without a starter. Liquid yeast (e.g. Wyeast, White Labs) offers a far wider range of strains but needs refrigeration and usually a starter. For high gravity lagers even dry yeast should be propagated or pitched at double rate.
Related terms: Yeast, Pitch Rate
EBC (European Brewery Convention) is the European unit for beer colour, measured optically at 430 nm. Higher numbers mean darker beer: Pilsner sits at 4 to 8 EBC, Märzen at 20 to 30, stout above 80. Colour can be estimated from grain weight and malt colour using formulas like Morey.
Related terms: SRM (Standard Reference Method), Malt, Roasted Malt
Esters are fruity aroma compounds yeast produces during fermentation from alcohols and organic acids (e.g. isoamyl acetate: banana, ethyl acetate: apple/solvent). Higher fermentation temperatures, high gravity and ester-active strains (Hefeweizen, Belgian yeasts) increase ester production. In lagers they are deliberately minimised by cold fermentation and clean strains.
Related terms: Yeast, Top-Fermenting (Ale), Witbier
Malt yield describes the maximum soluble extract a grain delivers, expressed as a percentage of dry mass or in Points per Pound per Gallon (PPG). Pilsner and pale ale malt sit around 80 to 82 %, while crystal and roasted malts are clearly lower. Combined with brewhouse efficiency it lets you predict the original gravity of a recipe.
Related terms: Brewhouse Efficiency, Malt
A fermenter holds the cooled wort and yeast, can be sealed airtight and is fitted with an airlock. Common types are PET or HDPE buckets, glass carboys, stainless steel kegs and conical fermenters in plastic or stainless. Conicals make it easy to drain trub and yeast.
Related terms: Airlock, Primary Fermentation
Final Gravity (FG) is the specific gravity or Plato reading after primary fermentation has finished. The difference between OG and FG defines alcohol content and apparent attenuation. Typical FG ranges from 1.008 to 1.012 for dry ales and noticeably higher for sweeter stouts or wheat beers.
Related terms: Original Gravity (OG), Alcohol By Volume (ABV), Attenuation
Hop additions are used differently depending on timing: First Wort Hops give a soft bitterness, bittering hops boil 60 to 90 min., late hops 0 to 15 min., whirlpool hops below 90 °C, and dry hops cold during or after fermentation. Longer boiling produces more bitterness, shorter contact more aroma. The total amount is controlled by the recipe with an IBU target.
Related terms: International Bitterness Units (IBU), Dry Hopping, Whirlpool
Pellets (Type 90) are milled and compressed cone hops with roughly 10 % better utilisation than whole cones and longer shelf life. Whole cones take more volume but act as a filter bed in the whirlpool. Type 45 pellets are concentrated and carry about twice the bittering compounds per gram.
Related terms: Hops, Alpha Acid
Hops (Humulus lupulus) are the dried flower cones of the female hop plant and provide bitterness, aroma and natural preservation. Bittering compounds (alpha acids) isomerise during the boil, while essential oils carry aroma and are added late or cold. Classic German varieties are Hallertau, Tettnang and Spalt, modern US varieties include Citra, Mosaic and Cascade.
Related terms: Alpha Acid, International Bitterness Units (IBU), Hop Pellets vs. Whole Cones, Dry Hopping
In an infusion mash all rests are reached by heating or by adding hot water in the same vessel. In a decoction mash a portion of the mash is removed, boiled and returned, which raises temperature without direct heating and adds more malt depth. Classic Pilsner and Bock are traditionally double or triple decocted, while most modern systems use infusion mashing.
Related terms: Mashing, Saccharification Rest
International Bitterness Units (IBU) measure isomerised hop alpha acids in milligrams per litre of beer. IBU depends on hop mass, alpha acid content, boil time and wort gravity, and is usually estimated with models such as the Tinseth formula. A Helles sits at 18 to 25 IBU, a Pilsner at 30 to 45, and an American IPA often between 45 and 70.
Related terms: Alpha Acid, Hops, BU:GU Ratio
An IPA is a hop-forward top-fermented beer with 5.5 to 7.5 % ABV and 40 to 70 IBU. Modern American IPA features tropical and citrus US hops (Citra, Mosaic, Centennial) over pale ale malt with a slightly caramel base. English versions are earthier, more restrained and built around crystal malt.
Related terms: NEIPA (Hazy IPA), Hops, Dry Hopping
The iSpindel is a floating, battery-powered open-source hydrometer that transmits its tilt angle (and thus specific gravity) over Wi-Fi from inside the fermenter. It delivers continuous fermentation curves without taking samples. It is calibrated with water and a sugar solution of known gravity.
Related terms: Refractometer vs. Hydrometer, Primary Fermentation
A keg is a pressure-rated stainless steel vessel (5 to 50 L) used to store, carbonate and dispense finished beer. Homebrewers mostly use Cornelius kegs (NC, 19 L) with ball-lock or pin-lock fittings. CO2 pressure allows forced carbonation, while a spunding valve enables natural carbonation under pressure.
Related terms: Spunding, Carbonation
Kölsch is a Cologne speciality and a hybrid top-fermented beer that is cold-conditioned after primary fermentation. It sits at 4.7 to 5.0 % ABV, 20 to 30 IBU and 6 to 8 EBC, with a clean, lightly fruity profile and a soft hop finish. The name is a protected designation of origin used by Cologne breweries.
Related terms: Top-Fermenting (Ale),
Krausen is the dense, foamy layer of CO2, hop resins, proteins and yeast that forms on the wort during primary fermentation. High krausen marks the most active phase after 24 to 48 hours. Once the krausen falls, primary fermentation is typically mostly complete.
Related terms: Primary Fermentation, Diacetyl Rest
A lauter manifold (often a flexible stainless steel coil) sits at the run-off port and holds back the grain bed during lautering. Alternatives are false bottoms or slotted tubes that act as filters. The goal is always an even grain bed that lets clear wort flow into the brew kettle.
Related terms: Lautering, Brew Kettle
Lautering separates the finished mash from the solid grain husks so that clear wort flows into the kettle. A typical lauter rest lasts 10 to 20 minutes, followed by run-off and sparging with water at 75 to 78 °C. A consistent grain bed and a slow, gentle flow are key to avoid haze and tannin extraction.
Related terms: Mashing, Lauter Manifold / False Bottom, BIAB (Brew in a Bag)
Malt is grain (mostly barley, sometimes wheat, rye or oats) that has been germinated and then dried (kilned). Malting develops enzymes that later convert starch into fermentable sugars during the mash. Depending on kilning temperature you get pale base malt (such as Pilsner) or heavily roasted speciality malt (such as roasted barley).
Related terms: Pilsner Malt, Munich Malt, Crystal / Caramel Malt, Roasted Malt
At 60 to 65 °C beta amylase is the dominant enzyme and breaks starch down into the fermentable disaccharide maltose. A longer maltose rest (45 to 60 minutes) yields a dry, well-attenuated beer with a lower final gravity. It is often combined with a saccharification rest.
Related terms: Saccharification Rest, Attenuation
Mash pH ideally sits at 5.2 to 5.5 (measured at 20 °C), because in this range malt enzymes work best and fermentation later runs cleanly. Hard, bicarbonate-rich water raises pH, dark malts and acidulated malt lower it. Corrections are made with acidulated malt, lactic acid or brewing salts like calcium sulfate and calcium chloride.
Related terms: Brewing Water, Acidulated Malt, Mashing
Mashing means mixing milled malt with warm water so that malt-derived enzymes break starch down into fermentable and non-fermentable sugars. It typically lasts 60 to 90 minutes at one or several rests between 50 and 78 °C. The grist-to-water ratio is usually 1 : 3 to 1 : 4 (kg/L).
Related terms: Infusion vs. Decoction, Saccharification Rest, Mash pH
Helles is a malt-forward bottom-fermented Munich beer at 4.7 to 5.4 % ABV, 18 to 25 IBU and 6 to 9 EBC. It tastes soft, bready and sessionable with subtle aroma of German noble hops. It is a textbook example of a beer where malt quality and water profile drive the character.
Related terms: Munich Malt, Bottom-Fermenting (Lager)
Munich malt is a base malt kilned at higher temperatures (15 to 25 EBC) that delivers an intense, malty and bready character. It can make up to 100 % of the grist because it still carries enough enzymes for conversion. Typical use is in Munich Dunkel, Märzen and Festbier.
Related terms: Malt, Munich Helles
New England IPA (NEIPA) is a hazy, soft and hop-driven IPA at 6 to 7.5 % ABV. Typical features are high oat and wheat shares, low boil bitterness (about 30 to 50 IBU) and intense whirlpool plus dry hop additions of fruit-forward varieties. The mouthfeel is juicy and almost creamy thanks to biotransformation during fermentation.
Related terms: IPA (India Pale Ale), Dry Hopping, Whirlpool
Original Gravity (OG) measures the concentration of fermentable and non-fermentable extract in the wort before fermentation, expressed in degrees Plato (°P) or specific gravity (e.g. 1.040 to 1.080). It is the most important number for predicting alcohol content, since ABV roughly equals (OG, FG) × 131. Standard lagers sit around 11 to 12 °P, doppelbocks at 18 °P and above.
Related terms: Final Gravity (FG), Alcohol By Volume (ABV), Plato vs. Specific Gravity, Attenuation
Pale ale malt is a slightly more kilned English base malt (5 to 8 EBC) with a noticeable bready note and fuller body than Pilsner malt. Its enzymatic power is usually enough to convert added speciality grains as well. It is the classic base for American Pale Ale, IPA, Bitter and ESB.
Related terms: Malt, Pilsner Malt, IPA (India Pale Ale)
Pilsner is a pale, bottom-fermented beer at 4.5 to 5.2 % ABV, 30 to 45 IBU and 6 to 10 EBC. The German version is dry, lean and noble-hopped (Saaz, Tettnang), while the Bohemian version is fuller and softer. It requires soft water, Pilsner malt and 4 to 8 weeks of cold lagering.
Related terms: Pilsner Malt, Bottom-Fermenting (Lager)
Pilsner malt is the lightest German base malt at 2 to 4 EBC with very high enzymatic power. It is kilned at low temperatures (around 80 to 85 °C) and contributes a clean, slightly grainy character. It forms the backbone of Pilsner, Helles, Kölsch and many pale ales, often as 95 to 100 % of the grist.
Related terms: Malt, Pale Ale Malt
Pitch rate describes how many yeast cells you add per millilitre of wort and per degree Plato. Rule of thumb: ales need around 0.75 million cells per ml·°P, lagers around 1.5 million cells per ml·°P. Dry yeast contains roughly 6 to 10 billion viable cells per gram.
Pitching describes adding yeast to the cooled and aerated wort. Key factors are the right pitching temperature (usually 1 to 2 °C below fermentation temperature), enough viable cells (pitch rate) and a healthy starter. Too little or weak yeast leads to long lag times, off-flavours and poor attenuation.
Related terms: Pitch Rate, Yeast, Wort Cooling
Degrees Plato (°P) expresses dissolved extract as mass percent, while Specific Gravity (SG) measures density relative to water. Rule of thumb: °P × 4 is roughly the last two digits of SG, so 12 °P matches about 1.048. Plato is common in Europe, SG dominates in the US and UK.
Related terms: Original Gravity (OG), Final Gravity (FG)
Primary fermentation is the phase in which yeast consumes most of the extract and produces alcohol, CO2 and fermentation aromas. It typically takes 4 to 7 days at 18 to 22 °C for ales and 7 to 14 days at 8 to 12 °C for lagers. You can see it through krausen, an active airlock and falling gravity readings.
Related terms: Secondary / Bottle Conditioning, Krausen, Attenuation
A protein rest at 50 to 55 °C activates proteolytic enzymes that cut long protein chains into smaller pieces, affecting head retention and clarity. With modern, well-modified malt the rest is mostly unnecessary and can actually hurt foam. It still makes sense for high amounts of wheat or rye in the grist.
Related terms: Mashing, Maltose Rest
Both instruments measure wort extract. A hydrometer needs 100 to 250 ml of sample and reports SG or Plato directly. A refractometer only needs a drop or two, but its readings must be corrected once alcohol is present (i.e. after fermentation begins), because alcohol alters refraction.
Related terms: Original Gravity (OG), Final Gravity (FG)
Roasted malts are produced by heating kilned or raw grain to 200 to 230 °C and contribute dark, coffee to chocolate-like flavours. Typical examples are Carafa Special (de-husked roasted malt), Chocolate Malt and Roasted Barley. They are used sparingly (1 to 8 %) and shape stout, schwarzbier and porter.
A saccharification rest at 70 to 75 °C primarily activates alpha amylase, producing larger, less fermentable sugars and dextrins. It contributes residual sweetness, body and mouthfeel. An iodine test after 10 to 20 minutes confirms whether starch conversion is complete.
Related terms: Maltose Rest, Mashing
Secondary or bottle conditioning ferments residual sugar or added speise/priming sugar inside the bottle or keg, producing natural carbonation. It usually takes 1 to 3 weeks at 18 to 22 °C depending on the style. A maturation or cold storage phase typically follows at lower temperatures.
Related terms: Carbonation, Speise (Reserved Wort),
Speise is unfermented wort taken aside before pitching and stored cleanly so that it can prime the beer after primary fermentation. Typical dosage is around 80 to 130 ml per litre of beer, depending on gravity and final attenuation. Compared to table sugar it carbonates more harmoniously and avoids foreign sugars.
Related terms: Carbonation, Secondary / Bottle Conditioning
Spunding closes the fermenter near the end of primary fermentation with a pressure-holding valve (spunding valve) so that the last 0.5 to 1 °P of fermentation builds CO2 that stays dissolved in the beer. This avoids speise or forced carbonation and gives clean natural carbonation. It requires pressure-rated fermenters such as stainless cylinders or Cornelius kegs.
Related terms: Carbonation, Secondary / Bottle Conditioning, Keg (Cornelius / KEG)
SRM is the colour scale used in the United States. The conversion is approximately EBC ≈ SRM × 1.97, so a Pilsner at 4 SRM matches roughly 8 EBC, and a stout at 40 SRM matches around 80 EBC. SRM and EBC use the same optical method, only the scale differs.
Related terms: EBC Colour, Malt
Stout is a dark, top-fermented beer with roasted, coffee and chocolate notes, classically between 4 and 7 % ABV. The colour (60 to 120 EBC) comes from roasted barley and chocolate malt, while the body ranges from lean Dry Stout (Guinness style) to full-bodied Imperial Stout. Hops mostly act as a backbone bitter component.
Related terms: Roasted Malt, EBC Colour
Top-fermenting yeast (Saccharomyces cerevisiae) works at 16 to 24 °C and collects at the surface of the fermenter near the end of fermentation. It produces fruity esters and phenols and ferments quickly, often within 4 to 7 days. Ales such as IPA, wheat beer, stout, Saison and Kölsch belong to this group.
Related terms: Bottom-Fermenting (Lager), Yeast, Esters
After the boil the hot wort is set into a circular motion so that trub and hop debris settle in the centre of the kettle as a cone. This makes it easier to draw off clear wort. Whirlpool hop additions at 75 to 90 °C add lots of aroma with little bitterness and are typical for IPA and NEIPA.
Related terms: Boiling the Wort, Hop Addition, IPA (India Pale Ale), NEIPA (Hazy IPA)
Witbier is a Belgian white beer based on unmalted wheat and Pilsner malt, spiced with curaçao orange peel and coriander. It is hazy, sits at 4.5 to 5.5 % ABV, 10 to 17 IBU and tastes fresh, citrusy and lightly spicy. The Belgian top-fermenting yeast adds phenolic clove notes.
Related terms: Top-Fermenting (Ale), Esters
The hot wort needs to be cooled to pitching temperature (8 to 22 °C depending on yeast) as quickly as possible to avoid hot side aeration, DMS formation and infection. Plate, immersion or counterflow chillers usually take 15 to 30 minutes. Only after cooling do you aerate and pitch the yeast.
Related terms: Boiling the Wort, Pitching
Brewer's yeast is a single-cell fungus that converts sugar into alcohol and CO2 and shapes much of the flavour profile (esters, phenols, sulfur). It comes as top-fermenting (Saccharomyces cerevisiae) and bottom-fermenting (Saccharomyces pastorianus) strains, plus wild yeasts such as Brettanomyces. Each strain has documented temperature ranges, attenuation and pitch rates.
Related terms: Top-Fermenting (Ale), Bottom-Fermenting (Lager), Pitch Rate
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