One of the most obvious differences between cognac and whiskey is that cognac makers use grapes, and whiskey makers use grains. Although both processes use fermentation to create the liquors, cognac makers use a double distillation process. Government regulations require that cognac makers create the liquor solely in the region of Cognac in France, using only certain species of grapes. Whiskey makers are free to make whiskey in many countries, and some countries, such as Ireland and the United States, are famous for their whiskey.
As with many foods, cognac and whiskey have a long history of development and refinement. Cognac differs from other fruit-based liquors because wine makers double distill it and age it in oak barrels. The double distillation, called charentaise distillation, creates a less harsh drink. Cognac shipped in oak barrels, or casks, is more flavorful and smoother because of the time it sits in the barrels on ships and in storage.
Similarly, the Irish and Scottish people had to improvise when making liquor and created whiskey. The scarcity of grapes on the islands prompted the creation of the grain-based liquor. They used the grains that were available, and over time the process was refined to include aging in barrels. Aging the fermented liquid in oak barrels is common to cognac and whiskey. In some areas, including Ireland, people use the word whisky; in the United States and other areas, the drink is called whiskey.
Cognac makers ferment grape juice for about five days before the first distillation. After the second distillation, the makers seal the cognac in barrels. Usually, they list the cognac age as Very Special (VS), which means a minimum of two years in the barrel; Very Special Old Pale (VSOP), which is four years or more; or Extra Old (XO), which is stored in the barrel more than six years. Some cognac makers age their products for more than 20 years.
In contrast, whiskey makers distill the grain mash only once and list the age in years. For example, a label may say 12-year whiskey. Some of the common ages are five, 10 and 15 years. A similarity between cognac and whiskey is that connoisseurs judge each one's age by the amount of time spent in the barrel, not in a bottle.
Another difference between cognac and whiskey is that cognac makers use the juice of only select grapes, but not other fruits. Generally, whiskey makers use barley as a base, but may use other grains as well. These grains include rye and malted rye, wheat, and corn. Often whiskey makers combine grains, such as in bourbon whiskey, that features corn as more than half of the grain.