a cheaper and more efficient distillation of whisky. In 1850, Andrew Usher began producing a blended whisky that mixed traditional pot still whisky with that from the new Coffey still. The new distillation method was scoffed at by some Irish distillers, who clung to their traditional pot stills. Many Irish contended that the new product was, in fact, not whisky at all. By the 1880s, the French brandy industry was devastated by the phylloxera pest that ruined much of the grape crop; as a result, whisky became the primary liquor in many markets. 20th century During the Prohibition era in the United States lasting from 1920 to 1933, all alcohol sales were banned in the country. The federal government made an exemption for whisky prescribed by a doctor and sold through licensed pharmacies. During this time, the Walgreens pharmacy chain grew from 20 retail stores to almost 400. Production Distillation A still for making whisky is usually made of copper, since it removes sulfur-based compounds from the alcohol that would make it unpleasant to drink. Modern stills are made of stainless steel with copper innards (piping, for example, will be lined with copper along with copper plate inlays along still walls). The simplest standard distillation apparatus is commonly known as a pot still, consisting of a single heated chamber and a vessel to collect purified alcohol. Column stills are frequently used in the production of grain whisky and are the most commonly used type of still in the production of bourbon and other American whiskeys. Column stills behave like a series of single pot stills, formed in a long vertical tube. Whereas a single pot still charged with wine might yield a vapour enriched to 40–60% alcohol, a column still can achieve a vapour alcohol content of 95.6%; an azeotropic mixture of alcohol and water. Aging Whiskies do not mature in the bottle, only in the cask, so the "age" of a whisky is only the time between distillation and bottling. This reflects how much the cask has interacted with the whisky, changing its chemical makeup and taste. Whiskies that have been bottled for many years may have a rarity value, but are not "older" and not necessarily "better" than a more recent whisky that matured in wood for a similar time. After a decade or two, additional aging in a barrel does not necessarily improve a whisky. While aging