How Whiskey is Made
Whiskey production varies depending on the style being made, the country where it originates, and other factors, but the general process remains the same in most cases. The process involves choosing a grain, fermenting it, distilling the liquid, then aging the liquid.
Grain Selection and the Mixture (The Mash Bill)
Each distillery has its own recipe for the grain mixture, that recipe is called the “Mash Bill.” The primary grains in the mash bill are either Barley, Rye, Corn, Wheat, or a mixture of those elements.
Barley
Barley is a cereal grain that was originally native to Asia. Barley was very important in ancient times and was one of the first grains to be widely cultivated. However, when leavened bread became popular, consumption of barley was replaced by wheat and rye. Having a lower gluten content (which provides the framework for dough to rise), the application of barley in the production of bread is limited. As such, fewer people today in developed countries eat barley. Although, the discovery that barley is high in beta-glucan has given rise to its use in health-promoting food products, especially foods tailored to cardiovascular health. Barley grows in either “6 row” or “2 row” varieties, and whiskey distillers will choose which variety they use based on the characteristics of the whiskey the produce.
A large proportion of the world’s barley supply is used make beer. Barley does however remain a staple food for many people in less developed countries such as those in North Africa and in areas where wheat is difficult to grow, such as Tibet.
The term “Green Barley” simply means “Unmalted barley,” and refers to barley that is taken straight off the plant and used, instead of being malted. The Redbreast brand is a whiskey that uses unmalted barley in its mash bill
Rye
Rye came into cultivation later than wheat, barley, and oats and was not known to the ancient Egyptians and Greeks. It was the main grain used for bread-making in Northern Europe and Russia for many centuries. This is partly because it grows well in colder, harsher climates and partly because it was preferred by some people.
Scandinavian countries such as Denmark, Norway and Sweden eat a variety of bread and crispbreads made from rye flour, although wheat products are becoming more popular.
Rye contains less gluten than wheat flour, and this makes rye bread significantly denser. Traditional rye breads are made with a sourdough method so have a slightly sour taste when compared to wheat bread. Dark rye flour bread is all whole grain flour. Light rye grain bread is a mixture of whole grain rye flour and refined rye flour. Bread made wholly from rye flour is made in Germany and called pumpernickel
Corn
Corn (also known as maize), is one of the sweetest tasting grains. In its immature form it is the familiar yellow corn on the cob. When it matures and dries out it is used like other grains to make grain foods like breakfast cereal and tortillas. It is one of the world’s most important crops because it is used widely in food manufacture.
Corn is unique in that it cannot reproduce itself without the aid of humans – its seeds cannot be released because they are tightly wrapped around the ear. Wild corn has never been found and domesticated corn was probably developed through hybridization.
Wheat
Few distilleries add wheat to their mash bill (e.g. Bernheim or Maker's Mark). Wheat makes a whiskey milder and smoother on the tongue. If wheat is added, it makes up about 10% of the mash bill.
Malting
All whisky starts as raw grain—in the case of malt whisky, barley, which has to be specially treated to access its sugars. The barley is moistened and allowed to partially sprout, or germinate, a process called malting which secretes an enzyme that converts the barley’s starches to sugars. Germination is cut off when the barley is dried by heating.
Mashing
The sugars contained in the grain must be extracted before fermentation, and this is done through mashing. The grains that are being used—like corn, wheat, or rye—are ground up, put in a large tank (called a mash tun or tub) with hot water, and agitated. Even if the distiller isn’t making malt whisky, some ground malted barley is typically added to help catalyze the conversion of starches to sugars. The resulting mixture resembles porridge. Once as much sugar as possible has been extracted, the mixture—now known as mash or wort (if strained of solids)—moves on to the fermentation stage.
Fermentation
Fermentation occurs when the mash/wort meets yeast, which gobbles up all the sugars in the liquid and converts them to alcohol. This takes place in giant vats, often called washbacks. The process can take anywhere from 48 to 96 hours, with different fermentation times and yeast strains resulting in a spectrum of diverse flavors. The resulting beer-like liquid—called distiller’s beer or wash—clocks in at around 7%-10% ABV before it goes into the still.
Distillation
The process of distilling increases the alcohol content of the liquid and brings out volatile components, both good and bad. Stills are usually made of copper, which helps strip spirits of unwanted flavor and aroma compounds. The two most common types of stills—pot stills and column stills—function differently. Both are outlined below.
Pot Still Distillation
Pot stills are used in the production of whiskies—usually, though not always, malt whiskies—from Scotland, Ireland, the United States, Canada, Japan, and elsewhere. Pot still distillation is a batch process. Some styles use double-distillation, while others are distilled three times.
The wash goes into the first still, often called the low wines still, where it’s heated up. Alcohol boils at a lower temperature than water, so the alcohol vapors rise off the liquid and into the still neck and lyne arm, eventually reaching the condenser, which turns them to liquid once again. The resulting liquid, which is about 20% ABV, goes into the second still, or spirit still, where the process is repeated. At this time, a third distillation can occur. The resulting final spirit comes off the still starting at around 60%-70% ABV. The distiller discards or reserves a certain amount of spirit from the beginning and end of the run, known as heads and tails, due to their unwanted flavors and aromas. The rest—known as the heart—goes into barrels, often by way of a spirit safe
A Pot Still
A Column Still
Column Still Distillation
Column stills, also known as continuous or Coffey stills, are typically used to produce bourbon, rye, and other American whiskeys, as well as grain whiskies from Scotland, Ireland, Canada, Japan and elsewhere. The column still works continuously and efficiently, removing the need for the batch process of pot stills.
The distiller’s beer is fed into the column still at the top and begins descending, passing through a series of perforated plates. Simultaneously, hot steam rises from the bottom of the still, interacting with the beer as it flows downward, separating out the solids and unwanted substances, and pushing up the lighter alcohol vapors. When the vapors hit each plate, they condense, which helps get rid of heavy substances like congeners and increases the alcohol content. Eventually, the vapor is directed into a condenser. Column stills can produce spirit up to 95% ABV, although most whiskies are distilled to lower proofs.
Maturation
Nearly all whiskies are aged in wood—usually oak—containers (known as casks or barrels). One notable exception is corn whiskey, which may be aged or unaged. Bourbon, rye, and other types of American whiskey must be aged in new charred oak barrels, while for other countries’ styles, the type of oak and its previous use are generally left up to the producer. Barrels are stored in warehouses, and as the whisky matures, some of the alcohol evaporates (usually about 2% a year is lost). This loss, or evaporation, is affectionately known as the "Angel's Share,” and it creates a distinct (and lovely) smell in the warehouse. The whisky that remains will have also lost some of the original (ABV) strength and if filled at 63% it will, after three years, have dropped to around 55-60%.
Some whiskies, such as scotch, have a required minimum age. The whisky may be left to mature for more years, or bottled, depending upon many factors including quality, standard age expressions for that distillery, economics (the bean-counters always have their say) and the whims or choices of the Master distillers and blenders.
Different types of casks
Casks / Barrels
The casks themselves are usually made from either American White Oak or European Oak as these have proven to be the best for whisky maturation. Although 'new oak' has been used, current thought is that previously-used casks help add more character to the whisky and the ones in widespread use today are ex-bourbon or ex-sherry casks.
American law dictates that casks may only be used once for bourbon maturation, so these are a sensible and very common option for Scotch whisky as they are dismantled and shipped to Scotland after that single use.
Sherry casks are, obviously, made from European Oak and sourced in the major sherry-producing regions of Spain. The first time a sherry cask is used for whisky it is referred to as 'First Fill', then second-fill ... etc.
The color of a whisky is highly dependent upon the type of cask used. Bourbon casks will produce much lighter-colored whiskies than sherry casks, but some producers also use artificial coloring (caramel) to help darken their products. Flavor is also dependent upon the types of cask used. As bourbon casks are charred on the inside, these carbon deposits help filter the impurities from the spirit during maturation and also help produce vanilla flavors in the resulting whiskies, whereas sherry casks help produce richer, dark fruit (like raisin, prune & currant) flavors in the whisky, along with stronger wood (oak) and sherry ones. Obviously, first-fill casks produce richer flavors than second-fill ones, and so on.
Bottling
Once matured, whisky is bottled at a minimum of 40% ABV. The whisky may be chill-filtered or filtered in another way to prevent it from becoming cloudy when cold water or ice is added. For most large whisky brands, a bottling run combines a number of barrels—anywhere from a few dozen to hundreds—from the distillery’s warehouses. When only one barrel is bottled at a time, it’s labeled as single cask or single barrel.
Original Distillery Bottling (OB)
Whisky which is bottled directly for the producing distillery and not sold on to private individuals or independent bottling companies for them to bottle is known as an 'OB' or Original Distillery Bottling.
Many distilleries have set ages for bottling whisky which they believe best highlight their whisky's characteristics, so they bottle and sell the whisky at these ages.
Independent Bottling (IB)
Distilleries also sell casks to other companies for them to bottle and sell, or even to private individuals or clubs and societies. Once bottled these offerings are known as IBs or Independent Bottlings. Some of the more well known Independent Bottlers include Gordon & MacPhail (G&M), Signatory, Douglas Laing, Murray McDavid and Hart Brother's just to name a few.