Glossary

The Bourbon Lexicon

angels’ share: The liquid that evaporates from aging barrels (the proportion of whiskey and water depends on the barrel's location in the warehouse). Typically, about 10 percent of the total evaporates the first year, and 3 to 4 percent each year thereafter.

backset: A watery portion of a previously distilled mash that has been saved and is added (“set back”) to a new batch of fermenting mash (similar to a sourdough starter).

barrel proof: Bourbon that is bottled directly from the barrel without adding water to adjust the proof. Because of evaporation during aging, the proof is typically high.

beading: The formation of bubbles when a bottle of bourbon is shaken. The larger the bubbles that form at the top, the higher the proof.

beer: See distiller's beer.

beer still: A still used to produce low wines from distiller's beer. If it is a column still, it will be several stories high. If it is one of a series of pot stills, it will be the largest. The distillate is typically about 40 proof.

bonded bourbon (also bottled in bond): Originally, bourbon that was produced in a government-bonded warehouse for taxing purposes. Now it refers to a bourbon that is at least four years old and at least 100 proof. In addition, it must be the product of one distillery and one distiller in one season.

bottled in bond: See bonded bourbon.

bourbon: American whiskey made from a fermented grain mash that is at least 51 percent corn. Its final distillation can be no higher than 160 proof, and it must be put in new (unused) charred oak barrels at no higher than 125 proof. There is no age requirement. As soon as the whiskey touches wood, it becomes bourbon. Note that almost no bourbon made today is aged for less than four years. See also straight bourbon.

bung: The stopper used to seal a barrel. It is made of yellow poplar because it expands when soaked with liquid.

charring: The process in which the interior of a barrel is set on fire and allowed to burn for less than a minute. This cracks and blackens the wood, which allows the whiskey to penetrate the sides of the barrel.

chill haze: The cloudiness that appears at cool temperatures (such as when ice is added) if a bourbon is unfiltered or only lightly filtered.

congeners: The esters and fusel oils, mostly by-products of fermentation, that add flavor to bourbons. Tiny amounts are optimal; too much can produce off flavors.

continuous still: Another term for the beer still.

cooper: A barrel maker.

cooperage: Facility where barrels are made.

corn whiskey: Whiskey made from 80 to 100 percent corn mash and aged in used or uncharred barrels.

distillation: Production of alcohol through a series of steps involving evaporation and condensation.

distiller's beer: Liquid from the fermented mash that is ready to be distilled to make whiskey. The alcohol content is usually between 8 and 10 percent, or 16 to 20 proof.

dona tub: A container in which yeast is grown until it reaches sufficient volume to be added to the mash.

doubler: The copper still to which low wines from the beer still are added to produce high wines (i.e., new whiskey).

doublings: Another term for high wines.

esters: Aromatic organic compounds produced by yeast as a by-product of fermentation. They are responsible for many of the fruity and spicy flavors in whiskey.

expressions: Different versions of a whiskey brand that vary by age or proof. For example, Old Forester comes in 86- and 100-proof expressions.

fermenter: The large tank, typically made of stainless steel or cypress wood, in which cooked mash is fermented by yeast.

fusel oils: These alcohols, with a higher molecular weight than beverage alcohol, are present in tiny amounts in whiskey distillate. Higher amounts can produce off flavors.

heads and tails: The first and last distillates to come off the doubler, respectively. Since both contain impurities, they are returned to the still for further distillation. In some premium bourbons, the heads and tails are discarded rather than being distilled again.

Four Roses bottling line at Cox's Creek.

high wines: The spirits, also called new whiskey, produced in the doubler; they can be put into barrels for aging. High wines cannot be more than 160 proof.

low wines: The spirits produced by the first distillation of distiller's beer.

malted barley (or simply malt): Partially sprouted barley that is roasted to stop germination. It is added to the mash bill to facilitate fermentation, since barley contains enzymes not found in corn, rye, or wheat. These enzymes help the yeast convert starch to fermentable sugars and then to alcohol.

mash: The mixture of grains cooked in the mash tub until it resembles porridge.

mash bill: The recipe, or the proportion of each grain used to produce a particular whiskey.

mash tub: The large metal (usually stainless steel) vessel in which the grains are cooked.

master distiller: The bourbon maker assigned the overall responsibility for production and quality at a particular distillery.

mingling: The process of mixing bourbon from several barrels to create a consistent flavor profile. This is different from “blending,” which is the process of adding flavors or aged spirits to grain-neutral spirits. By law, bourbons are never blended.

new whiskey: The clear distillate from the final distillation that is put into barrels for aging. Also called high wine or doublings.

nose: The combination of aromas that can be detected by smelling bourbon in a glass. Equivalent to a wine's bouquet.

Prohibition: The period in American history when the sale of beverage alcohol was illegal. The Volstead Act was passed in 1919 to enforce the Eighteenth Amendment to the Constitution, which made Prohibition federal law. Prohibition was repealed on December 5, 1933, with ratification of the Twenty-First Amendment.

Top of the column still at Four Roses Distillery in Lawrenceburg.

proof: Measure of the percentage of alcohol in a beverage, based on a 200-point scale. Thus, 90-proof bourbon is 45 percent alcohol by volume. The term (and the numbers) originated in the nineteenth century when buyers, seeking to verify that their whiskey had not been diluted, would mix it with gunpowder and light it. It would burn only if the whiskey was at least 50 percent alcohol, thus providing 100 percent “proof” that it was undiluted.

rackhouse (also rickhouse): A warehouse where bourbon is stored for aging.

rectified whiskey: Spirits mixed and sold by a rectifier.

rectifier: Historically, a spirits dealer who purchased whiskies from one or more distillers and mixed them to make the desired product. This practice was common in the nineteenth century, when most distilleries were small and could make a profit only by selling to rectifiers.

red layer: The layer of caramelized wood sugars formed when a barrel is charred. This gives bourbon its color and much of its flavor.

repeal: The end of Prohibition, which took effect on December 5, 1933, when Utah became the thirty-fifth state to ratify the Twenty-First Amendment to the Constitution. Repeal was made possible by the Blaine Act, introduced to Congress by Senator John Blaine of Wisconsin.

ricks: The scaffolding made of wooden beams on which aging barrels rest in a warehouse.

rye whiskey: Whiskey made from a mash bill containing at least 51 percent rye.

setback: See backset.

single barrel: Whiskey bottled from a single barrel. The yield can range from 60 to 150 750-mL bottles, depending on how long the whiskey was aged and how much was lost to evaporation.

small batch: Whiskey bottled from the mingling of a small number of barrels. There is no prescribed number: some distilleries make small batches from as few as ten barrels, and others may use a hundred or more.

small grains (or smalls): The grains other than corn, usually malted barley and rye or wheat, used to make bourbon and Tennessee whiskey.

sour mash: See backset.

spent mash: The grain residue left over after fermentation; also known as spent beer or stillage. Because spent mash is rich in carbohydrates and proteins, many distilleries sell it or give it away to local farmers, who use it for animal feed.

spirit safe: A glass-walled brass box that allows distillers access to distilling spirits to measure the density. Otherwise, the safe is kept locked.

straight bourbon: Bourbon that has been aged at least two years before bottling.

sweet mash: Mash fermented without the addition of backset.

tails: See heads and tails.

Tennessee whiskey: Whiskey that is almost identical to bourbon, with the same mash bill and aging requirements, but before it is put in the barrel, it is filtered through sugar maple charcoal. The two remaining distilleries that produce Tennessee whiskey are located in (surprise!) Tennessee: Jack Daniels (in Lynchburg) and George Dickel (in Cascade Hollow near Tullahoma).

thief: A copper tube that can be inserted into a barrel of aging whiskey to extract a sample for evaluation.

thumper: A second still to which uncondensed low-wine vapors from the beer still are added and bubbled through hot water before being condensed and distilled into high wines. It has the same function as a doubler.

toasting: Process of heating oak staves so they can be bent to make barrels.

Volstead Act: See Prohibition.

warehouse staining: Dark coloring on the walls of warehouses and other structures near a distillery that results from the growth of a harmless microscopic fungus, Baudoinia compniacensis, that feeds on evaporated alcohol.

Culture of Old Forester's proprietary yeast strain in the Early Times Distillery lab.

wheated bourbon: Bourbon in which wheat has been substituted for rye in the mash bill.

yeast: Microscopic, single-celled fungi (Saccharomyces cerevisiae) that feed on the sugars present in mash. The by-products of their digestion are ethyl alcohol, carbon dioxide, heat, and a variety of fruity-smelling compounds (esters), depending on the yeast strain. Some distilleries, such as Brown-Forman, propagate their yeast on-site from frozen or liquid cultures. Others, including Buffalo Trace, add cakes of dry yeast directly to their fermenters.