First, boil ground corn in fresh spring water and some backset, or sour mash, saved from a previous fermentation. (Kentucky’s distillers make a big deal of their pure limestone water, but its main advantage is simply its lack of iron, which would make whiskey bitter and black.) Next add rye or wheat, which will contribute flavor, and cook that at a lower temperature. Then add malted barley—barley that has been partially germinated to generate enzymes that convert starch to sugar. In Maker’s Mark the proportions are 70 percent corn, 16 percent wheat, and 14 percent barley; in Wild Turkey they’re about 75 percent corn, 13 percent rye, and 12 percent barley. Cook about three and a half hours in all.
After the resulting mash has cooled, pump it into fermentation vats (traditionally cypress tanks that look like exceptionally deep hot tubs but today usually made of stainless steel) typically holding ten of thousands of gallons apiece. Add some more backset and a quantity of homegrown yeast. (Jim Beam’s yeast colony goes back to around Prohibition. Maker’s Mark’s is actually older; it was preserved through the dry years by Bill Samuels’s grandfather.) This mixture will go to work on itself, and the mash will taste like sweet breakfast cereal after one day, somewhat sour after two days, and like flat beer after three. As the yeast turns sugar into alcohol and carbon dioxide, and the latter churns up from the bottom, the top of the vat roils and bubbles. No stirring is necessary.
After several days of this you’ve got your beer, which is about 8 to 11 percent alcohol. Pump it up to the top of your four- or five-story-high column still, ideally a lovely copper one made by Vendome Copper & Brass Works in Louisville. As the liquid trickles down, heat it to a carefully controlled temperature between the boiling point of alcohol (173 to 176 degrees) and that of water (212) so it emits a vapor with less water, more alcohol, and just the right concentrated flavor. Condense the vapor, and the resulting “low wine” is about 55 or 60 percent alcohol.
Next distill that condensed vapor again, in a still more like a pot still, called a doubler . This raises the alcohol level to between 65 and 80 percent. The resulting “high wine,” or “white dog,” is ready to be barreled.
First cut it with distilled water to bring it to no more than 62.5 percent alcohol (125 proof). Then pump it into new, charred fifty-three-gallon white oak barrels. Then store for several years. (The barrels at the top of a warehouse, where it gets hotter, will age faster than those below, and distillers have various ways of dealing with this. Maker’s Mark and Wild Turkey rotate their barrels; everybody else takes some sort of a cross section from around the warehouse. To make a smallbatch or single-barrel bourbon, pull from the very middle of the warehouse, but don’t pull too much or you may compromise the quality of your ordinary bourbon by denying it your finest barrels.)
When you’re ready for bottling, select the barrels of whiskey you’ll combine, dump their contents together, filter it, cut with distilled water to bottle proof, and bottle.
Don’t do any of this without a federal license.