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"
American whiskey it is aged, it must be aged in used or uncharred oak barrels "at not more than 62.5% alcohol by volume (125 proof)". In practice, if corn whiskey is aged, it is usually aged in used bourbon barrels. Straight whiskey is whiskey that was distilled to not more than 80% alcohol by volume (160 proof) that has been aged for at least two years at a starting alcohol concentration of not more than 62.5%. It has not been blended with any other spirits, colorings, or additives. A straight whiskey that also meets one of the other above definitions is referred