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A Glossary of Bourbon & Whiskey Terms


A Glossary of Bourbon & Whiskey Terms

Whiskey has its fair share of lingo. Curious about what “sour mash” really means, what Bottled-in-Bond is really all about, or the difference between single malt Scotch and blended malt Scotch? Read on!


ABV: Stands for alcohol by volume, a measure of the alcoholic strength of the whiskey, and is expressed as a percentage.


American whiskey: Any whiskey made in the United States.


Barrel: While it’s often used generically to describe any cylinder-shaped wooden container used for aging whiskey, “barrel” technically refers to the 53-gallon containers used in the United states to age bourbon and rye. Barrels are made from oak, usually American white oak, and, in the case of bourbon and rye, charred on the inside.


Blending: The artful mixing of different whiskeys to create a cohesive whole. Blending doesn’t always produce “blended whiskey” in the legal sense; any whiskey that’s not a single cask is the product of some kind of blend, including single malts and your favorite big-name bourbons. Barrell Craft Spirits is captivated by the sometimes alchemical reactions that can take place by introducing one whiskey to another. Experience that magic for yourself by exploring our Barrell Craft Spirits line, or by trying some of our special releases like Armida or Dovetail.


Bottled-in-bond: An American labeling term dating back to the 1897 Bottled-in-Bond Act, which refers to a whiskey that’s the product of one distillation season at one distillery, is aged at least four years, and is bottled at 100 proof, or 50% alcohol.


Bourbon: A kind of American whiskey made in the United States from a mash of at least 51% corn, distilled to no more than 160 proof, aged at a proof no higher than 125 in new, charred oak barrels, and bottled at no less than 80 proof. In addition to corn, most bourbon is made with a small amount of malted barley, and then a third grain, often called the “flavor grain.” Rye is the most common third grain, but some use wheat instead–these are often called wheated bourbons–and a still smaller number use both.


Cask: Any of the many sizes of oak containers used to age whiskey, wine, beer, and other beverages. Casks can be as small as five gallons, or as large as 150 gallons. Barrels are one particular size of cask. Notably, casks are made without nails or glue, instead relying on a tight fit and the strength of the iron hoops around the outside to hold them together.


Cask strength: Whiskey that was bottled without any dilution, at exactly the strength it emerges from the cask. All of Barrell Craft Spirits’ whiskeys are bottled at cask strength for maximum flavor.


Charring: The interior of bourbon barrels are exposed to open flame for up to a minute to develop a layer of char. The intensity of this char contributes to the color, flavor, and aroma of the whiskey.


Chill filtration: A process that involves chilling a whiskey to sub-freezing temperatures, then filtering it to remove oils that can cause a whiskey to get cloudy. The result is a whiskey that stays clear, even when it’s cold, but can sometimes have less flavor and a thinner mouthfeel. We don’t chill filter any of our whiskeys at Barrell Craft Spirits.


Corn whiskey: A quirky category of American whiskey that must be distilled from a mash of at least 80% corn and aged in used and/or uncharred oak casks.


Column still: Column stills look like, well, columns. Wash is routed into the middle of the column, where it encounters steam and plates that separate it into fractions of varying alcoholic strengths. Column stills can be run continuously, as opposed to pot stills, which have to be emptied and reloaded between batches, so they’re sometimes referred to as continuous stills. They’re widely used to make bourbon and rye, and to produce grain whisk(e)y in the British Isles.


Distilling: The process that transforms fermented wash into new-make spirit. In very simple terms, here’s how it works. A solution of water and alcohol (like beer or wash) is heated up. Because alcohol has a lower boiling point than water, the vapor generated is higher in alcohol than the original solution. That vapor is captured and condensed, resulting in a distillate that’s stronger in alcohol. Notably, all fresh distillates are clear. All of whiskey’s color, and much of its character, comes from the barrel itself.


Irish whiskey: Irish whiskey refers to any whiskey distilled from cereal grains in Ireland to no higher than 94.8% alcohol by volume, aged at least three years in wooden casks, and bottled at no less than 40% alcohol. There are several subcategories:

Single Malt Irish Whiskey: An Irish whiskey made at a single distillery from 100% malted barley and distilled on a pot still.

Single Pot Still Irish Whiskey: An Irish whiskey made at a single distillery from a mash of malted and unmalted barley and distilled on a pot still.

Single Grain Irish Whiskey: An Irish whiskey made at a single distillery from any grain or any mix of grains and usually distilled on a continuous column still.

Blended Irish Whiskey: Any mix of multiple Irish whiskey styles, or of the same style from multiple distilleries.


Malt: Malted grain has been tricked into starting to sprout by moisture and temperature, then stopped before it actually grows a plant by heat. The process generates enzymes that distillers can use to turn grains’ starches into fermentable sugars. Barley is the most commonly malted grain, but it’s possible to malt rye, wheat, and even corn, too.


Mash: The mixture of grain, water, and yeast that will be fermented and distilled to make whiskey.


Mash bill: The grains or mix of grains that are fermented to make whiskey.


Pot still: The type of still you probably imagine when you think of a still, with a big pot as the base narrowing to a vertical neck. Widely used in the British Isles to make malt whisk(e)y, and sometimes used in the United States.


Proof: A measure of the alcohol content in whiskey. In the United States, the proof of a whiskey is twice the percentage of alcohol by volume. For example, an 80 proof whiskey is 40% alcohol. Can also be used as a verb to refer to the process of adding water to reduce the strength of a whiskey.


Rye whiskey: An American whiskey adhering to almost all the same rules as bourbon, with one notable exception: instead of at least 51% corn, the mash bill must be at least 51% rye.


Scotch whisky: Scotch whisky, like Irish whiskey, must be produced in Scotland, distilled to no higher than 94.8% by alcohol, and aged at least three years in wooden barrels to earn the name “whisky.” And, like Irish whiskey, there are several different varieties:

● Single malt Scotch whisky: Scotch whisky made at a single distillery from a mash of 100% malted barley and distilled on a pot still.

● Single grain Scotch whisky: Scotch whisky made at a single distillery from a mash of any grain or combination of grains, and usually distilled on a column still

● Blended malt Scotch whisky: A mix of two or more single malts.

● Blended Scotch whisky: A mix of two or more single malt and single grain whiskies.

● Blended grain Scotch whisky: A mix of two or more single grain whiskies.


Single barrel: Means the whiskey in the bottle came from one single maturation barrel, and wasn’t blended with any other barrels of whiskey.


Small batch: This popular labeling term has no legal definition; at Barrell, we use it to refer to our one-time-only blends of bourbons, ryes, American whiskeys, and rums, each of which are assembled through painstaking experimentation from casks we source from some of the world’s best producers.


Sour mash: A distilling technique that uses a small amount of an older fermentation to start the next fermentation, akin to a sourdough or yogurt starter. The process is said to ensure consistency from batch to batch; it doesn’t make a sour-tasting whiskey.


Straight whiskey: A designation applying to American whiskeys that are distilled to no higher than 160 proof, matured for at least two years, and, if blended, are blended only from whiskey produced in the same state.


Tennessee whiskey: Tennessee whiskey follows all the rules of bourbon, plus two more: It must be made in Tennessee, and it must undergo the “Lincoln County process,” which involves filtering the new-make whiskey through maple charcoal before maturation.


Wash: The fermented mash. Also referred to as “beer”– and, indeed, it often tastes and smells a bit like a sour, cloudy, not particularly tasty beer.


Wheat whiskey: A kind of whiskey made in the United States from a mash of at least 51% wheat, distilled to no more than 160 proof, aged at a proof no higher than 125 in new, charred oak barrels, and bottled at no less than 80 proof.