Scotch whisky whisky used. An age statement on the bottle, in the form of a number, must reflect the age of the youngest whisky used to produce that product. A whisky with an age statement is known as guaranteed age whisky. Scotch whisky without an age statement may, by law, be as young as three years old. In the early 21st century, such "No age statement" whiskies became more common, as distilleries responded to the depletion of aged stocks caused by improved sales. Labels may also carry various declarations of filtration techniques or final maturation processes. A Scotch whisky labelled as "natural"
Bourbon whiskey oak containers for aging. In practice, these containers are generally barrels made from American white oak. The spirit gains its color and much of its flavor from the caramelized sugars and vanillins in the charred wood. Straight bourbon must be aged at least two years, and blended bourbon must contain at least 51% straight bourbon on a proof gallon basis (i.e., most of the alcohol in the blend must be from straight bourbon). The remainder of the spirits in a blended bourbon may be neutral grain spirits that are not aged at all. If a product is labeled merely as