American Whiskey Classifications
There are several classifications of American whiskey, including straight, bottled-in-Bond, and light whiskey:
Straight: This type is aged in white, charred oak barrels at 160 proof or less and aged at least two years. It is blended with water to no less than 80 proof and must be 51 percent grain by volume. About half of US consumption is straight whiskey.
Bottled-in-Bond: According to the Bottled Bond Act of 1894, American straight whiskey can be housed free of taxes while it ages, and is not taxed until it is removed from the warehouse to be sold.
It must be aged a minimum of 4 years, although most is aged longer. It is bottled at a minimum of 100 proof, and placed in a "bonded warehouse," completely under direct supervision of the Internal Revenue Service. Taxes are paid when the whiskey is released from the holding warehouse.
Light: This type is stored in standard or uncharred new oak containers and is between 161 and 189 proof. Blended light whiskey is mixed with less than twenty percent straight whiskey, and is made of corn. This classification is the newest, established in 1972.
Bourbon: Born in America, Bourbon is a variety of whiskey made with the addition of at least 51 percent of corn and must be aged in charred white oak barrels for at least 2 years by law in the United States. It is also known as corn whiskey.
What does liquor "proof" mean?
"Proof" in the United States, is exactly twice the level of pure alcohol by content.
If a liquor is labeled 100 proof, it is 50 percent alcohol. Aging of all whiskeys is done in the barrels prior to bottling, not after. The longer it is aged, the smoother the whiskey.