Spirits distinguish themselves from beer, wine and other fermented beverages by being distilled. Fermentation occurs naturally – wild yeasts may accidentally find rotting fruit and convert its sugars to alcohol – while distillation requires more intentional processing. Some of the oldest evidence for distillation can be found among ancient civilizations in China, Egypt and Mesopotamia where medicines, perfumes and other elixirs were created through distillation processes.
Distillation involves boiling liquid, vaporizing it and collecting fractions at specific temperatures depending on the substance being distilled. Ethanol (potable alcohol) with the highest boiling point is desired as its product, while unwanted congeners with lower boiling points may be separated out through secondary distillation. Distillation continues until all fractions have been collected.
An additional collection vessel can then be connected to the system, evacuated and attached back with taps to collect another fraction. This process can continue until all fractions have been collected and your desired ethanol product has been extracted from storage.
George Washington may receive credit for making whiskey a commercial success, but it was actually a Scottish farm manager who introduced distilling to America. He convinced his boss at Mount Vernon to experiment with distillation using crops and water supplies available there – convincing them even further by convincing his employer to provide a copper still to aid the process.