What Is Alcohol?

Alcohol, in the beverage world, means one specific molecule: ethanol (C₂H₆O). It is produced by yeast fermenting sugars, and it is the only alcohol safe for human consumption in moderate amounts. Other alcohols — methanol, isopropanol — are toxic even in small doses.

Ethanol is a small, versatile molecule. It is soluble in water and in fat, which is why it carries flavor so well and why it affects the brain so quickly: it crosses the blood–brain barrier within minutes.

We measure the strength of a spirit as ABV (alcohol by volume) — the percentage of the liquid, at 20 °C, that is pure ethanol. A bottle labeled 40% ABV contains 40 mL of ethanol in every 100 mL of liquid. In the US you may also see proof, which is simply ABV × 2 (so 40% ABV = 80 proof).

Ethanol has almost no color and only a faint, sweetish smell. Everything else you taste in a spirit — vanilla in bourbon, juniper in gin, smoke in Islay whisky — comes from the raw materials, the yeast, the water, aging, or the still. Ethanol is the vehicle; flavor is the passenger.