On a family farm, cracked corn, yeast, sugar, and water were put into a wooden barrel to ferment. The solids were removed, and the liquid was poured into the kettle and heated over a wood fire. Because alcohol boils at a lower temperature than water, the first steam to pass through the worm was alcohol. Cold stream water flowing over the worm returned the alcohol to liquid, which flowed into the jug. In an attempt to increase the proof, some distillers ran the alcohol through an intermediate “thump barrel.” Whiskey is alcohol that has been aged in a charred oak barrel.