Single malt whisky (and sometimes a third) time. The final spirit, called "new make spirit", generally has an alcohol content of 60 to 70%. Most new-make malt whisky is diluted to about 62.5% a.b.v. before it is placed in casks to mature. The "new-make spirit", or unaged whisky, is then placed in oak casks to mature. By law, all Scotch whisky must be aged for a minimum of three years in oak casks, though many single malts are matured for much longer. The whisky continues to develop and change as it spends time in the wood, and maturation periods of twenty years or
Whisky must be aged in new charred-oak containers, except for corn whiskey which does not have to be aged. If it is aged, it must be in uncharred oak barrels or in used barrels. Corn whiskey is usually unaged and sold as a legal version of moonshine. If one of these whiskey types reaches two years aging or beyond, it is additionally designated as "straight", e.g., "straight rye whiskey". A whiskey that fulfils all above requirements but derives from less than 51% of any one specific grain can be called simply a "straight whiskey" without naming a grain. US regulations recognize