BARREL: In the context of scotch, usually a standard American ex-bourbon barrel, which holds 53 gallons, or about 200 liters.
BUTT: The standard size for a sherry cask, which holds 132 gallons, or about 500 liters. Sherry butts are usually made of American oak.
CASK: The generic term for a wooden container, typically rounded, with flat ends, that is used to age whisky.
CASK STRENGTH: Literally, the strength of a whisky when it comes out of a cask as measured by the amount of alcohol by volume. Typically, a whisky labeled “cask strength” has been slightly adjusted with water to maintain consistency across a batch. Nevertheless, the term connotes a high alcohol by volume.
CONGENER: The generic term for the parts of a distillate other than water and ethanol, usually present in trace amounts. Spirit stills are used partly to separate out the desirable congeners from the undesirable ones.
DUNNAGE HOUSE: A large, low warehouse, typically with earth floors and stone walls, used to age whisky.
FINISH: After a whisky has been aged, a distiller may choose to “finish” it in a cask that previously held wine, beer, or other spirits to impart some of those liquids’ qualities to the whisky.
HOGSHEAD: A cask holding 66 gallons, or 250 liters. Hogsheads are typically rebuilt standard American barrels, with added staves and heads to increase their size.
KILN: A type of furnace used to dry barley after it has begun to germinate. Kilns traditionally used peat for fuel, though today it is usually natural gas.
MALT: Barley that has been allowed to begin germinating, but is then dried over a heat source to stop it from sprouting. The malting process allows a barley seed to produce the enzymes needed to convert the seed’s starch into sugar.
MASH: A combination of grain and hot water produced in a mash tun, the result of which is a sugar-rich liquid called wort.
MASH TUN: The vessel in which mash is produced. These days, it is usually made of stainless steel.
PEAT: Semi-decomposed plant matter, which can be cut into bricks and burned for fuel. Peat is found worldwide, but in Scotland it is prized, as it was traditionally used to dry barley that has begun to sprout. Today peat is unnecessary, but still used frequently because it imparts a pungent, smoky aroma and flavor to a whisky.
PIPE: A cask used to age port, it’s rounder and squatter than a sherry butt, though they hold the same volume of liquid—132 gallons, or 500 liters.
PROOF: In the United States, proof is an alternative measure of a beverage’s alcohol by volume, defined as two times the A.B.V. (A 100-proof whisky is 50 percent alcohol.) In Britain, 100 proof is traditionally defined as the alcohol content necessary to allow gunpowder to burn when it is doused in the liquid—namely, 57 percent. So 100 proof in British terms is equivalent to 114 proof in American terms. These days, though, Britain simply lists the A.B.V. on the bottle.
QUARTER CASK: A barrel that holds 21 gallons, or 80 liters.
RACKHOUSE (OR RICKHOUSE): Uncommon in Scotland, a rackhouse is a multistory facility used to age whisky.
SHERRY: A variety of fortified wines produced in the Jerez region of Spain. Sherries range from dry and crisp to thick and sweet. Sherry was immensely popular in nineteenth-century Britain, and the constant flow of Sherry shipping casks provided whisky distillers with a ready source of containers for aging—though over time sherry casks became especially prized for the influence residual sherry soaked into the wood had on the whisky. As the sherry industry declined, distillers began to “rent” sherry—essentially subsidizing the industry—in order to keep up its supply of sherry casks.
STILL (WASH, SPIRIT): There are two types of stills. A pot still is, essentially, a pot with a conical top, out of which runs a metal pipe. The whisky wort is added in batches and then cooked; the alcohol, some water, and trace amounts of congeners boil off and are collected once they cool down. A continuous still, also known as a Coffey, patent, or column still, is a column with a heat source at the bottom and a metal pipe at the top; as the wort is introduced at the mid-level, it drops to the bottom to be vaporized, and what rises to the top is captured in a manner similar to a pot still. The advantage is that the still can be used constantly, hence the name. Typically, a distillery will have two or three stills per set—the “wash” still, to strip most of the water and unwanted elements off, and one or two “spirit” stills, to refine and fine-tune the spirit.
WASH: Essentially, unhopped beer. Wash is the result of adding yeast to wort; the yeast eat the sugar in the wort, producing alcohol. Once the yeast have died off, the wash can be distilled.
WASHBACK: A vessel, traditionally made of Oregon pine but these days more often made of stainless steel, in which wort and yeast are combined to produce a wash.
WORT: The sugar-rich liquid produced from a mash, to which yeast is added to produce alcohol.