Distillation Terminology Glossary

18th Amendment

The 18th Amendment to the United States Constitution established Prohibition. It made it illegal to produce, transport, and sell alcoholic beverages. However, it did not ban the consumption or private possession of alcohol.

21st Amendment

The 21st Amendment repealed Prohibition by overturning the 18th Amendment. It officially ended the nationwide ban on alcohol that had been in effect since January 17, 1920.

ABV (Alcohol by Volume)

ABV stands for Alcohol by Volume and measures the ethanol content of a beverage as a percentage of its total volume. It indicates how much alcohol is present compared to the overall liquid. Brewers and distillers use ABV to classify strength, regulate labeling, and guide drinkers in understanding potency.

For homebrewers, learning to calculate ABV is essential for quality control and recipe consistency. A higher ABV usually means a stronger beverage, though flavor and body also play important roles in perception.

Interested in mastering this important skill? Read our article, “Demystifying ABV Calculation: How to Determine Alcohol by Volume in Your Homebrewed Mash,” to learn practical tips and methods for accurate measurement.

Acetaldehyde

Acetaldehyde is a chemical byproduct of fermentation. It is often perceived as the aroma and flavor of green apples in beer.

Acetone

Acetone is a colorless, volatile, and highly flammable compound with a sharp, pungent aroma. It often appears at the start of distillation, carried over in the early vapor fractions. Because of its low boiling point, acetone is typically among the first substances to evaporate when heating a fermented mash.

In brewing and distilling, removing these early fractions—commonly referred to as “the foreshots”—helps improve the purity and safety of the final product. Proper technique ensures that unwanted compounds like acetone are separated before collecting the drinkable spirit.

Acid Rest

Traditional brewers perform an acid rest early in the mash at around 95°F. This step helps lower the mash’s pH and prepares it for proper fermentation.

Acrospire

The acrospire is the shoot that emerges from a barley grain during germination. Its growth is a key indicator of the malting process.

Adjunct

An adjunct is any unmalted grain or fermentable ingredient used in brewing. Common adjuncts include rice, corn, honey, and syrups. Mass-produced American lagers often use adjuncts to create lighter flavors.

Aeration

Aeration introduces oxygen into the wort at different brewing stages. It promotes healthy yeast fermentation when done before fermentation. After fermentation, however, aeration can cause off-flavors like cardboard or paper aromas due to oxidation.

Aging

Aging refers to the process of storing distilled spirits in wooden barrels, most commonly oak, to enhance their flavor and complexity. During this time, the spirit interacts with the wood, extracting compounds that contribute to its aroma, taste, and color. Aging can mellow harsh characteristics, adding smoothness and depth over months or years.

Different types of barrels, char levels, and aging environments significantly influence the final flavor profile. Many distillers carefully monitor the aging process to achieve a specific taste and character in their finished product.

Air Lock

An air lock is a simple valve used during fermentation to allow carbon dioxide to escape while preventing outside air and contaminants from entering. It protects the fermenting beverage from unwanted bacteria and wild yeast. Air locks are essential tools for maintaining clean, healthy fermentation in brewing and distilling.

Alcohol

Specifically ethyl alcohol or ethanol, is the primary intoxicating component of beer. Alcohol content varies widely in beer, from under 3.2% ABV to over 14%, with most craft beers averaging around 5.9% ABV.

Alcohol by Volume (ABV)

ABV measures the alcohol content as a percentage of total liquid volume. It’s calculated by subtracting the final gravity from the original gravity and dividing by 0.0075. For instance: (1.050 – 1.012) ÷ 0.0075 = 5% ABV.

Alcohol by Weight (ABW)

ABW measures the alcohol content based on the weight of alcohol per volume of beer. It is always lower than ABV. To calculate ABW: (1.050 – 1.012) ÷ 0.0095 = 4% ABW.

Alcoholic

The term “alcoholic” refers to two things:

• A warming taste of ethanol and higher alcohols perceived as spicy or vinous in character. Higher ABV beers tend to have a fuller mouthfeel and noticeable alcohol aromas and flavors.

• A person suffering from a disabling disorder marked by compulsive, uncontrolled alcohol consumption.

Alembic

An alembic is a traditional type of copper still design used for distilling spirits. Its simple, efficient shape allows it to separate alcohol from fermented mash with precision, influencing the flavor and purity of the final product.

Amylase

Amylase is an enzyme that breaks down starches into fermentable sugars during the brewing or distilling process. Without this critical step, yeast would not be able to convert starch into alcohol.

Azeotrope

An azeotrope is a mixture of two or more liquids that boils at a constant temperature and maintains a consistent composition between liquid and vapor. This unique behavior makes separation by simple distillation extremely difficult, often requiring advanced methods to achieve full separation.

Backings (Singlings or Low-Wines)

Backings are the result after running beer through a thumperless still once. They contain a good percentage of alcohol but usually lack the strength to hold a bead, indicating lower proof.

Backins or Back-ins

Backins (or back-ins) is another term for backings. See the Backings definition above for full details.

Backset

Backset is what remains in the still after distillation is complete. In rum production, this leftover liquid is called “dunder” and is sometimes reused to develop deeper flavors in future fermentations.

Bale

A bale refers to a wire or chain secured across the top of the still’s cap. It helps keep the cap in place during the distillation process, preventing dangerous blow-offs when pressure builds.

Barrel/Cask-Aging

Barrel or cask-aging involves storing distilled spirits in wooden barrels, often oak, which may be new, charred, or previously used to age other spirits. Aging in wood mellows harsh elements and adds both color and complex flavors to the spirit.

Batch Distillation

Batch distillation is the process of distilling a fixed amount of mixture at one time. After the batch is processed, the still must be refilled before another run can begin.

Beer

Beer refers to the fermented liquid created from cornmeal bases and other ingredients. When cooked in the still, this beer becomes the foundation for producing moonshine.

Blending

Blending is the art of combining different distillation cuts to create the best possible final spirit. It requires skill and careful tasting to balance flavors, aromas, and mouthfeel.

Blockaders

Blockaders were men who produced and transported moonshine, often illegally. The term originated during historical periods of military blockades and later evolved to describe those who defied alcohol restrictions, giving rise to the term “blockade whiskey.”

Blubber

Blubber describes the bubbles formed when moonshine in a proof vial is shaken vigorously. Observing how the bubbles behave can help estimate the spirit’s proof.

Boiler

The boiler is the main body of the still where the mash or beer is heated. As the liquid boils, alcohol vapors rise and move into the distillation system for collection.

Boiling Flask (Pot Still)

A boiling flask, often used in pot still setups, is the container that holds the liquid mixture for distillation. In simple systems, it serves as the only vessel used for heating and vapor collection.

Boiling Chips

Boiling chips are small, porous stones added to liquids during heating. They help create a smooth, even boil by promoting bubble formation and preventing dangerous superheating or bumping.

Boiling Point

The boiling point is the temperature at which a liquid changes into vapor under a specific pressure. Knowing the boiling points of different compounds is critical to effective separation during distillation.

Bootlegger

A bootlegger is someone who sells moonshine or legally produced spirits under illegal circumstances. This practice often involves evading taxes, licenses, or regulatory controls.

Breaks at the Worm

“Breaks at the worm” describes the moment when the distillate exiting the worm coil falls below 100 proof. At this point, the spirit will no longer hold a proper bead and may signal the end of collecting high-quality cuts.

Brix Scale

The Brix Scale measures sugar content in liquids and is widely used in brewing, winemaking, and distilling. To learn more about how it affects your brews, check out our article: “Unlocking the Secrets of the Brix Scale: A Guide to Measuring and Mastering Sugar Content in Brewing.”

Busthead and Popskull

Busthead and popskull are slang terms for harsh whiskey that causes violent headaches. Poor distillation techniques and unremoved impurities often lead to these unpleasant side effects.

Cap (Two Meanings)

The cap is the top third of a still and is typically removable, allowing easy filling after a run. In fermentation, “cap” also refers to the foamy krausen that forms on the surface of fermenting liquid, signaling active fermentation.

Cap Arm

The cap arm is the copper pipe that connects the still’s cap to the next section. Its main role is to convey steam from the boiler to the condenser or column.

Cape

The cape is the bulge in the main body of a still. This area marks the point of greatest circumference, helping influence vapor flow during distillation.

Collar

A collar is the connection point between the cap and the body of the still. It ensures a secure, airtight fit to maintain pressure and proper vapor movement.

Condensation

Condensation is the process where a gas or vapor cools and transitions back into a liquid state. It is a vital step in both brewing and distilling.

Condenser

A condenser cools and transforms vapor back into liquid. Essential in distillation setups, common condenser types include the worm, dephlegmator, Liebig, and shotgun designs.

Congeners

Congeners are chemical compounds produced alongside ethanol during fermentation. These substances significantly influence a spirit’s aroma, flavor, and mouthfeel—sometimes positively, sometimes negatively.

Continuous Distillation

Continuous distillation introduces a constant feed of mixture into the system while continuously removing the separated products. It is widely used in industrial-scale operations for its efficiency.

Conversion

Conversion, or saccharification, is the enzymatic process where starches are broken down into fermentable sugars. Without this crucial step, fermentation would not yield alcohol.

Cuts

Cuts refer to the four stages of the distillation run: foreshots, heads, hearts, and tails. Collecting distillate in small containers helps distillers identify the shift between these stages before final blending.

Dead Devils

Dead devils are tiny bubbles seen in the proof vial when whiskey has been sufficiently proofed. When dead devils appear after shaking the vial, it’s time to stop adding water or low-wines.

Degrees Lintner

Degrees Lintner measures the diastatic power of malt, or its ability to convert starch into sugar. While it technically applies to any amylase activity, it usually reflects the combined strength of alpha- and beta-amylase enzymes.

Dephlegmator

A dephlegmator is a specialized condenser designed to fully or partially condense rising vapors in a distillation column. It plays a major role in plated column setups. Learn more in our article, “Understanding the Dephlegmator: Enhancing Distillation Efficiency.”

Diastatic Power (DP)

Diastatic power, measured in degrees Lintner, indicates the enzymatic strength of malted grains. High diastatic power means more efficient conversion of starches into fermentable sugars during mashing.

Distillate

Distillate is the condensed liquid collected after distillation. It contains the separated and purified components from the original mixture, including alcohol and flavor compounds.

Distillation

Distillation separates components of a liquid mixture by exploiting their different boiling points. Heating vaporizes the more volatile elements, which are then condensed back into liquid form for collection.

Distillation Column

A distillation column is a tall, vertical structure used primarily in fractional distillation. It contains trays or packing material that enhance vaporization, condensation, and the separation of various components.

Dog Heads

Dog heads occur when beer is nearly ready for distillation and begins to erupt into large, convulsive bubbles. These dramatic bubbles rise one after another, signaling an imminent run.

Doubled and Twisted

Doubled and twisted describes whiskey that has been distilled twice. In older still setups, all the singlings were saved and re-distilled together, significantly increasing the spirit’s strength.

Doubler/Thumper

A doubler or thumper is an airtight container placed between the boiler and condenser of a pot still. It boosts the proof of the spirit during a single distillation run without needing a second full run.

Ethanol

Ethanol is the specific type of alcohol found in alcoholic beverages. It is a clear, colorless, flammable oxygenated hydrocarbon with the chemical formula C₂H₅OH. In its pure (anhydrous) state, ethanol boils at 78.5°C. When mixed with water, it forms a binary azeotrope that boils at 78.15°C at 95.57% ethanol by weight.

Eutectic Mixture

A eutectic mixture consists of substances that melt or solidify at a lower temperature than any of their individual components. This unique property can complicate separation processes during distillation.

Faints or Feints

Faints, also known as feints, refer to the weak alcohol left over after distillation. They often include tails, and sometimes a mix of heads and tails, collected for re-distillation. Feints are low in alcohol but can be recycled to strengthen future batches.

Fermentation

Fermentation is the anaerobic conversion of sugars into alcohol and carbon dioxide by yeast. This essential process lies at the heart of brewing and distilling.

Fermenter

A fermenter is the vessel where mash fermentation occurs. It holds all the mash ingredients and provides an environment for yeast to convert sugars into alcohol.

Filter

Filters are devices or methods used to remove unwanted particulates or congeners from liquids. Effective filtration improves clarity, stability, and flavor quality.

Final Gravity

Final Gravity (FG) is the hydrometer reading taken after fermentation is complete. Comparing it to original gravity helps calculate the alcohol content in the finished product.

Flake Stand

A flake stand is a container through which cold water constantly flows to cool and condense steam. It houses the worm coil, condenser, or radiator, depending on the distillation setup.

Flavoring

Flavoring involves the intentional addition of extracts, fruits, or essences to a spirit. This technique enhances or modifies the final aroma and taste profile.

Foreshots

Foreshots are the first portion of liquid to emerge from the still during distillation. They often contain volatile compounds like methanol and should be discarded.

Fractional Distillation

Fractional distillation uses a fractionating column to perform multiple vaporization-condensation cycles within one run. This method is especially effective for separating compounds with similar boiling points.

Funnel

A funnel aids in transferring liquids, often holding a filter material through which whiskey passes into jars, jugs, or bottles.

Furnace

A furnace is the stone or brick structure where the still rests during heating. It provides even, controlled heat necessary for efficient distillation.

Fusel Oil

Fusel oils are bitter, oily byproducts of fermentation. Made up of higher alcohols and other congeners, fusel oils are generally undesirable and can negatively impact flavor.

Goose Eye

A goose eye refers to a good bead in the proof vial that holds firm for an extended time. It’s often used to estimate alcohol strength visually.

Grain Bill

A grain bill is the combination and specific ratios of grains used in a whiskey recipe. Different grains contribute unique flavors, body, and sugar content to the final spirit.

Headache Stick

The headache stick is the long rod, often used inside a thumper setup. It gets its nickname from the throbbing headaches poor-quality spirits can cause if distillation isn’t properly managed.

Heads

Heads are the second fraction collected during distillation. They contain lighter compounds and higher alcohols, some of which may be undesirable if left in large amounts.

Hearts

Hearts represent the third and most desired cut during distillation. This fraction contains the cleanest, smoothest alcohol and defines the true character of the final spirit.

Heater Box (Pre-Heater)

A heater box, or pre-heater, warms fresh beer before it enters the still for distillation. Preheating improves efficiency by reducing the amount of heat needed during the initial stages.

High Shots

High shots refer to extremely strong, untempered whiskey. These early cuts can sometimes measure close to 200 proof before dilution or blending.

Hydrometer

A hydrometer measures the density of liquids compared to water. Brewers use a saccharometer to measure sugar content during fermentation, while distillers use an alcoholmeter to measure spirit strength. Learn more in our article, “Mastering the Triple-Scale Hydrometer: Your Complete Guide to Precision Brewing.”

Infusion

Infusion involves steeping fruits, spices, or botanicals directly in finished spirits to add flavor. The process varies depending on the ingredient and desired intensity, but usually requires days or weeks to fully develop.

Krauesen

Krauesen is the thick layer of foam that forms on the top of a mash or wash during active fermentation. It signals strong yeast activity and healthy fermentation progress.

Long Thump Rod

A long thump rod is an open-ended copper pipe that conveys steam into the bottom of the thump barrel. The steam is then released, aiding in secondary distillation and proof improvement.

Low Wines

Low wines are the result of a stripping run. This low-ABV liquid contains alcohol, flavors, and impurities and is typically redistilled to produce a cleaner, higher-proof spirit.

Malt

Malt is grain that has been germinated, sprouted, dried, and ground. During malting, enzymes are activated that later convert starches into fermentable sugars. Drying the sprouts halts the process, preserving the grain until it’s rehydrated during mashing.

Mash

Mash is a mixture of ground grains, malt, water, and yeast. Some distillers also use the term to describe fruit-based mixtures prepared for fermentation.

Mash Stick

A mash stick is used to break up the cap that forms over the mash and to stir its contents. Often crafted with a crook at the end, it may have holes drilled and pegs inserted to form a comb-like tool. Some mash sticks are simply embedded with nails to aid stirring.

Mashing

Mashing is the process of cooking grains and converting starches into fermentable sugars. This step is critical in both brewing and distilling for creating alcohol-rich washes.

Mash Tun

A mash tun is a large, heat-resistant vessel used to mix a mash or wash. It often doubles as a fermenter in smaller distillery setups.

Moonshine

Moonshine refers to illicitly produced distilled spirits made without paying taxes. Nicknames for moonshine include ruckus juice, white lightning, corn squeezin’s, thump whiskey, and blockade whiskey, among many others.

Oaking

Oaking is the process of adding color, flavor, and complexity to spirits by aging them with oak chunks, staves, or chips, often inside glass containers.

Original Gravity

Original Gravity (OG) is the first hydrometer reading taken before fermentation begins. It measures the density of sugars in the wash and predicts potential alcohol yield.

Parrot

A parrot is a device attached after the condenser arm that holds an alcoholmeter. It allows real-time monitoring of the alcohol content flowing from the still.

Peated

Peated refers to malted barley dried over peat fires. Spirits labeled as peated, such as certain Scotch whiskies, often have a distinctive smoky aroma and flavor.

Plug Stick

A plug stick is a hickory or white oak rod with a bundle of rags attached at one end. The rags jam into the slop arm, sealing the bottom of the still during operation.

Poitín

Poitín is traditional Irish moonshine, historically untaxed and often made illegally. It shares cultural roots and methods similar to American moonshine.

Pot Still

A pot still is a traditional distillation device, typically made of copper, used to craft whiskey and brandy. It’s designed for a quick passage of vapor with minimal reflux. To learn more, read our article, “From Ancient Origins to Timeless Craft: Unveiling the Rich History and Art of Pot Stills in Liquor Distillation.”

Pot-Tail

Pot-tail, also known as slop, refers to the leftover, spent material remaining after a distillation run is completed.

PPG (Points per Pound per Gallon)

PPG measures the available gravity points in a grain, sugar, or brewing recipe. Understanding PPG helps brewers optimize sugar extraction. Dive deeper in our article, “Gravity Points 101: The Importance of PPG in Brewing History and Practice.”

Proof

Proof measures the alcohol concentration in a distilled spirit. It’s a traditional system used alongside ABV to indicate strength. See also the term “Temper” for a related meaning.

Proof Vial

A proof vial is a glass tube used to assess the bead of whiskey when shaken. Bateman Drop bottles, which held exactly one ounce, were historically popular. Today, rye flavoring bottles or government gauges are often repurposed for this function.

Racking

Racking is the process of transferring mash or wash from one container to another. It helps separate the liquid from sediment and promotes cleaner fermentation.

Rectification

Rectification purifies or refines a liquid through repeated distillation or fractionation. Each cycle removes more impurities, resulting in a cleaner, higher-proof spirit.

Reflux

Reflux involves returning condensed vapor back to the distillation column. It stabilizes temperature and improves component separation, especially during fractional distillation.

Reflux Still

A reflux still uses a distillation column to facilitate greater separation of compounds. This design produces a more refined and higher-proof final distillate.

Relay Arm

The relay arm is the pipe connecting the bottom of the relay barrel back into the still. It allows liquids and vapor to move between sections efficiently.

Relay Barrel (Dry Barrel)

A relay barrel, often a 50-gallon drum, connects the cap arm, relay arm, and thump rod. It catches “puke” during boiling and returns it to the still, preventing contamination or product loss.

Rig

A rig refers to an entire distillation setup, including the still, thumper, condenser, and associated piping.

Run (or A Run)

A run describes a complete distillation cycle. Common expressions like “He’ll make us a run” stem from the process of boiling a still’s contents through completion.

Sediment

Sediment forms when suspended particles settle to the bottom of a fermenter. Proper racking removes this layer to produce cleaner spirits.

Singlings

Singlings are another term for backings, referring to the product of an initial distillation run.

Slop

Slop is the weak liquid left in the still after distillation. It no longer holds a bead and is usually discarded or fed to livestock.

Sour Mash

Sour mash is made using backset, or pot-tail, from a previous distillation run. This method promotes yeast activity and flavor consistency.

Sparge

Sparging involves rinsing spent grains to extract as much fermentable sugar as possible after starch conversion is complete.

Specific Gravity

Specific Gravity (SG) measures the sugar concentration in a solution compared to water. Learn more in our article, “Brewing 101: Understanding the Magic of Specific Gravity.”

Spirit Run

A spirit run is the final, slow distillation pass intended to collect the cleanest, best-tasting alcohol from low wines.

Steam Distillation

Steam distillation introduces steam into a mixture to distill heat-sensitive components. It helps separate compounds with high boiling points without damaging them.

Still

A still is the container where beer is boiled during distillation. The term can also refer to the entire system, from boiler to flake stand. For more insight, check out our article, “Exploring the Art of Distillation: A Guide to the Different Types of Liquor Stills.”

Stripping Run

A stripping run is the first pass in a multi-run distillation. It strips alcohol from the mash to create low wines for later purification during the spirit run.

Swab Stick (or Toothbrush)

A swab stick is a thick hickory rod with a frayed, fibrous end. It stirs the beer while heating, preventing sticking or burning and ensuring even boiling.

Sweet Mash

Sweet mash is made with fresh water and new ingredients, without using backset. The first distillation run often starts with a sweet mash base.

Split Brandy

Split brandy is a mixture made from mash containing about one-quarter fruit content. It combines whiskey and brandy characteristics during fermentation and distillation.

Temper

Tempering reduces a whiskey’s strength by adding water or backings. This step typically adjusts spirits to around 100 proof.

Thump Barrel

A thump barrel, also called a thumper or thump-post, holds fresh beer. Steam from the still bubbles through it, doubling the strength before moving into the next stage.

TPW (Tomato Paste Wash)

TPW stands for Tomato Paste Wash, a simple, cost-effective sugar wash recipe often used by beginner distillers.

Tails

Tails are the final portion collected during a distillation run. They contain high levels of congeners and oils, often requiring careful blending or discarding.

UJSSM (Uncle Jesse’s Simple Sour Mash)

UJSSM is a popular, easy-to-make sour mash recipe designed by home distillers. It uses corn, sugar, yeast, and backset for consistency and rich flavor.

Vacuum Distillation

Vacuum distillation lowers the pressure during distillation, reducing the boiling points of components. It’s ideal for preserving heat-sensitive flavors.

Vapor Pressure

Vapor pressure measures the force exerted by vapor in equilibrium with its liquid form at a given temperature. It affects how easily a liquid evaporates.

Wash

Wash is a liquid mixture of sugars and yeast prepared for fermentation. It eventually becomes the alcoholic base for distillation.

Worm

A worm is the coiled copper condenser attached to a traditional pot still. Cold water surrounding the worm cools vaporized alcohol back into liquid form.

Wort

Wort is the sweet liquid strained from the mash tun. It contains fermentable sugars essential for brewing and distilling.

Yeast

Yeast is a single-celled fungus used in a fermentation. It consumes sugars and produces alcohol and carbon dioxide under anaerobic conditions. Yeast cells are also rich in protein and B vitamins.

If there is a term missing that you would like to see added to our distillation terminology glossary, please contact us!