All Scotch whisky is made from malted barley and aged in Scotland for no less than three years in an oak barrel. Scotch is double-distilled and often uses peated malt to impart a smoky flavour. Two main types of barrels used are American oak and French oak, which impart different nuances into the whisky as the spirit ages. Scotch can be single malt or a blend. Single malts are produced from 100% malted barley from one single distillery. A Scotch blend is made by combining whiskies from various distilleries and can be a blend of malted barley and grain whisky.