Alcohol distillation is an age-old practice, estimated to first have been utilized around 2000 BC. It was once used in Egypt, Mesopotamia and China to produce balms, essences and perfumes – including embalming of dead bodies – Queen Cleopatra is said to have written extensively on this subject!
Distillation begins with fermented liquids such as beer, wine or fruit juice that has undergone fermentation. The initial materials chosen depend on what spirit will ultimately be created: whiskey is typically made of grain-based alcohol while gin and vodka typically have fruit or rice bases respectively.
Distillation requires heating both liquid and vapor to reach equilibrium, so as to maintain this ratio at its optimum. In order to do this effectively, energy must be continuously consumed. You can reduce this requirement by adjusting your reflux rate and column length.
As alcohol contains high vapor pressure levels, cooling systems play a critical role.
If the difference in boiling points between components A and B is minimal, the vapor produced from their interaction will initially contain high concentrations of component A; as it cools off it gradually decreases until eventually becoming almost pure alcohol and entering heads where heavy and funky flavors like cardboard and old towels reside.
To minimize this problem, the vapor is fed through a column that separates it from liquid. A partial vacuum may also be employed to keep air out; however, this may lead to leaks. Maintaining these conditions requires complex controls.