“Old Fashioned” — Bourbon, a bitters-soaked sugar cube, ice, and an orange zest. This beauty is the vintage Rolex of cocktails, and says that you are who you are, you believe what you believe, and take it or leave it. Confident, bold, brave, yet still willing to be social.”—
Proof is the percentage of alcohol by volume, doubled. For example, if a bourbon is 90 proof, that means it is 45 percent ABV. But where did the term “proof” come from?
According to bourbon historian Michael Veach, the term harkens back to a time when distillers “proved” a spirit by mixing it with gunpowder and setting it on fire.
“If it sputtered and smoked, it was determined that it was ‘under proof.’ If it burned too quickly with a high flame, it was ‘over proof.’ If it burned with a steady flame, then it was ’100 percent proved,’” he writes in Kentucky Bourbon Whiskey: An American Heritage. “This even burn happens when the alcohol content of the whiskey is 50 percent ABV.”