Science tangent incoming.
Alcoholic beverages cannot be concentrated by evaporating away the water in the mixture, because the alcohol evaporates faster than the water does. The process of producing concentrated alcohol out of dilute alcohol is known as distilling. (The distilling process can be used for any such separation of liquids, from fine scotch to nuclear waste.) There are many methods but they all follow the same basic steps:
1: get some mixture of liquids and put it in a container
2: heat it up gently. Chemicals in the mixture will boil off, proportionately speaking, in the order of their volatility, with the lightest, most volatile liquids first and the heaviest, most stable liquids last.
3: collect the vapor that comes off the top and let it condense and run down into a storage container. The condensed liquid will emerge in a continuum of proportions that can be separated into three broad phases. Each phase also contains some water, because the water will steam even if it doesn’t boil.
A) High percent of undesired light liquids. Low percent of desired liquid. Very low percent of undesired heavy liquids. In brewing, this is the “head,” and contains poisons and noxious-smelling chemicals along with volatile but harmless and pleasant aromatics.
B) Low percent of undesired light liquids. High percent of desired liquid. Low percent of undesired heavy liquids. In brewing, this is the “heart,” and is mostly ethanol.
C) Very low percent of undesired light liquids. Low percent of desired liquid. High percent of undesired heavy liquids. In brewing, this is the “tail,” and contains mostly harmless proteins and oils that have strong, often unpleasant flavor and can be hard to digest in high proportions.
A and C can be cycled back into future batches to avoid wasting their desired liquid component.
B can be distilled again and again to remove more of the undesired liquids. If you’re looking for purity, this is a good idea, but it comes with a price in brewing, since every time you distill you’re losing aromatics and flavor chemicals along with poisons and flavors. Distill it enough times, and it doesn’t matter whether you started with fine wine or old yeasty dishwater: ethanol is ethanol.
If all you’re looking for is fuel, you can keep all of A (those volatile chemicals burn nicely) and most of C, and re-distill it again and again until you have all the water out of it.
If you’re looking for whiskey, you do indeed start with beer. Well. Sort of. Most of the time, you start with a strained-out wheat or corn mash that is technically beer. A nasty unpasteurized low-quality beer without any of the hops flavors that make beer taste like beer… but beer. Then you distill it two or three times and are left with something not unlike a wheat-based vodka. At this point, you put it in an oak barrel and wait a long time for flavor chemicals in oak wood to dissolve into the alcohol and water mixture. At last, you open it up and add water until you dilute it to the desired proof, bottle it, and sell it to real Southern colonels, for it is now whiskey.
