Corn whiskey (sometimes Corn Liquor or "White Lightning") is an American liquor made from a mash made of at least 80 percent corn. Distinct from the typical American moonshine, corn whiskey uses a traditional mash process and is subject to the tax and identity laws for alcohol under CFR 27. Several commercial distillers such as Heaven Hill and Buffalo Trace have started to produce corn whiskeys for retail sale. The whiskey is typically distilled at a high proof (up to 160 proof). The unaged corn whiskey is then diluted with water to at most 62.5 percent alcohol by volume, but usually 40 percent alcohol by volume, and bottled for retail.
The whiskey can be aged in used or uncharred oak barrels, though this practice strays from traditional moonshining. Aging usually is brief, six months or less, during which time the whiskey absorbs color and flavor from the barrel while the off-flavors and fusel alcohols are reduced. A variant called Straight Corn Whiskey is also produced, in which the whiskey is stored in used or uncharred new oak containers for 2 years or more. Whiskeys produced in this manner and aged for at least 4 years can be designated bottled in bond if they meet further requirements.
^http://www.law.cornell.edu/cfr/text/27/5.22 “Corn whisky” is whisky produced at not exceeding 160° proof from a fermented mash of not less than 80 percent corn grain, and if stored in oak containers stored at not more than 125° proof in used or uncharred new oak containers and not subjected in any manner to treatment with charred wood; and also includes mixtures of such whisky.
^Smiley, Ian. Making Pure Corn Whiskey: A Professional Guide for Amateur and Micro Distillers. December 2003