Age statement
An age label describes time in oak before bottling. When blended ages differ, the youngest whisky generally determines the stated age; permitted detailed percentage statements are another option.
TTB age guidance, checked .
The words behind
the whiskey.
From the grain recipe to the label on the bottle. Plain definitions, small diagrams and links to the primary sources.
Open the index to jump to a term. Each definition includes its sources and check dates.
Find a term (30)
Alcohol by volume (ABV)
The share of a liquid’s volume that is alcohol. In U.S. proof notation, 50 percent ABV corresponds to 100 proof.
27 CFR 5.1, checked .
Angel’s share
Spirit that escapes from the barrel through evaporation during maturation.
KDA glossary, checked .
Backset
Liquid remaining from an earlier distillation that is returned to a later mash.
KDA glossary, checked .
Barrel entry proof
Strength when spirit enters its aging barrel. Bourbon enters new charred oak at no more than 125 proof. This differs from bottling strength.
27 CFR 5.143, checked .
Barrel proof
A regulated label term: bottling strength may be no more than 2 proof degrees below the strength when the barrels are emptied. Also called cask strength.
27 CFR 5.87, checked .
Bottled in bond
For bourbon, federal conditions include one distiller, one distillery and one distilling season; at least 4 years in wood; bottled at 100 proof. The rules also restrict alterations.
Strength and time in wood
100
- 100Bottled in bond. Bottled at 100 proof, which is 50 percent alcohol by volume
Two years, then four
24
- 2Straight bourbon. At least two years in wood (from What makes bourbon bourbon)
- 4Bottled in bond. At least four years in wood
27 CFR 5.88, checked .
Bourbon
U.S.-made whisky from at least 51 percent corn, distilled to 160 proof or less, entering new charred oak at 125 proof or less, and bottled at 80 proof or above.
Where bourbon’s numbers sit
80125160
- 80Into the bottle. Bottled at 80 proof or higher, which is 40 percent alcohol by volume
- 125Into the barrel. Enters new charred oak at no more than 125 proof
- 160Off the still. Distilled to no more than 160 proof
Proof is twice alcohol by volume in the United States. Details and sources are below.
27 CFR 5.143, checked .
Bung
The plug that closes a barrel’s opening.
KDA glossary, checked .
Char level
A cooper’s designation for the barrel’s burned interior layer. Char treatment can change extraction during maturation; a higher number is not an age or quality score.
Cooper’s research, checked .
Column still
A tall, continuously operated still where fermented distiller’s beer meets steam and alcohol-rich vapor is collected.
KDA production guide, checked .
Cooperage
The making of wooden barrels, or a workshop that makes them. Staves form the barrel’s curved sides.
Cooper’s products, checked . KDA: flavor and production, checked .
Distillation
Separation using heat: alcohol-rich vapor rises from fermented mash and is cooled back into liquid.
KDA: flavor and production, checked .
Distiller’s beer
The fermented mash sent to a still. It is a production-stage liquid, not finished bourbon.
KDA production guide, checked .
Fermentation
Yeast uses sugars in the mash, producing alcohol and carbon dioxide. Distillers’ chosen conditions influence the resulting spirit.
KDA: flavor and production, checked .
Mash
The cooked grain-and-water mixture used in whiskey production.
KDA production guide, checked .
Mash bill
The grain recipe: which grains are used and their proportions.
KDA production guide, checked .
Maturation
The time spirit spends interacting with its aging container. New charred oak contributes color and flavor as bourbon matures.
KDA: flavor and production, checked .
New make
Fresh unaged distillate, also called white dog, before barrel maturation.
KDA glossary, checked .
Non-chill-filtered
Bottled without the chilling-and-filtration treatment used to reduce compounds that can create haze. This term does not mean every form of filtration was omitted.
Distiller’s filtration guide, checked .
Pot still
A still that works through individual batches rather than a continuous flow.
KDA glossary, checked .
Proof
The U.S. alcohol-strength scale is twice alcohol by volume: 100 proof is 50 percent ABV.
Proof to alcohol by volume
100 proofequals50% alcohol by volume
In the United States, proof is twice alcohol by volume. Bourbon is bottled at 80 proof or higher.
27 CFR 5.1, checked .
Rickhouse
A warehouse where whiskey barrels rest during maturation; also called a rackhouse.
KDA glossary, checked .
Rye grain
One possible secondary grain in a bourbon mash bill.
KDA: flavor and production, checked .
Single barrel
Whiskey bottled from one individual barrel rather than a combination of barrels. The term alone does not specify bottling strength.
Producer’s single-barrel description, checked .
Small batch
A producer’s selected barrels combined into a batch. Read the producer’s description to understand the particular batch and its selection.
Producer’s batch description, checked .
Sour mash
A process that returns part of an earlier batch to a new mash.
Producer’s process description, checked .
Straight bourbon
Bourbon stored in new charred oak for at least 2 years. A straight designation does not establish a 4-year age or bottled-in-bond status.
27 CFR 5.143, checked .
Thief
A sampling tool used to draw spirit out of a barrel.
KDA glossary, checked .
Yeast
Living microorganisms that transform fermentable sugars into alcohol and carbon dioxide; different strains can influence whiskey’s flavor.
KDA: flavor and production, checked .