You may have heard the saying that all bourbons are whiskey, but not all are bourbon. For a whiskey to classify as bourbon it must be made in the U.S. While any state will do, most are made in Kentucky. In addition, its mash which is that mix of grains from which bourbon is distilled must comprise at least 51 per cent and no more than 79 per cent Indian corn. Most recipes use about 70 per cent corn, which gives it its nickname corn whiskey.
Besides corn, the other grains used in the making of bourbon include malted barley and either rye or wheat. Some Kentucky bourbon makers say the limestone spring water in that area of the state lends bourbon its distinctive flavor.
Bourbon must be aged at least two years in a new, charred oak barrel made from American White Oak. But many types of bourbon are aged four years or longer. Bourbon gains its color and much of its flavor from barrel aging. The charred wood provides caramelized sugars that add flavor to the whiskey. The barrels can only be used once for bourbon so many become furniture or firewood. Others are used for aging soy sauce, while most end up in the United Kingdom for their Scotch whiskies.
Bourbon barrels are stored in large, multi-storey warehouses called rick houses. The wood barrels expand and contract based on the weather outside which eventually penetrates these rick houses. Hot weather causes the pores of the wood to open up more and impart their flavor. The result is barrels on the top floor will have a slightly different flavor than those on lower floors.
Most distillers make their bourbon between 80 and 100 proof. This means it contains 40 to 50 percent alcohol by volume.