Bartending Basics: What is Proof and Distillation?
When you read about the production of alcoholic beverages, you see terms like proof and distillation thrown around. Proof is the strength of an alcoholic beverage. In the United States, the scale is 200 degrees, with each degree equal to 0.5 percent alcohol by volume. So a 100-proof spirit is 50 percent alcohol. A 200-proof spirit is after-shave, or 100 percent alcohol.
Distillation is the process of converting a liquid by heating it into a gas or vapor that is then condensed back into a liquid form. In the case of liquor production, the liquid is a blend of ingredients that have been fermented so that it contains some alcohol.
When you heat this liquid, the alcohol it contains vaporizes first (because alcohol has a lower boiling point than, say, water). So the vapor that's trapped and later condensed back into a liquid has a much higher alcohol content than the original liquid.
Distillation is usually performed by a still. Stills come in two basic types:
The pot still: A pot still is a copper or copper-lined vessel with a large bottom and a long, tapered neck connected by a copper pipe to a cooling spiral tube, which is the condenser. As the liquid boils, it evaporates. The vapor rises up to the condenser, cools, and returns to a liquid state with alcohol. Often, this process is repeated to achieve the right alcohol level.
The continuous still: Also known as a column still, patent still, and Coffey still, the continuous still has tall copper columns that continually trickle liquid down over many steam-producing plates. The vapor is drawn into vents and condensed. A continuous still performs under the same principles as a pot still but works with a constant flow of materials coming in and going out, which is great for mass production.