Distilling alcohol is the process of separating ethanol (drinking alcohol) from water and other compounds in a fermented liquid by heating it. Because ethanol boils at 78.2°C (about 173°F) and water boils at 100°C (212°F), heating a fermented mixture to the right temperature causes the alcohol to vaporize first. That vapor is then cooled, condensed back into liquid form, and collected at a much higher alcohol concentration than the original brew.
Every spirit you’ve ever had, whether whiskey, vodka, rum, or tequila, went through this process. Fermentation alone can only produce beverages up to about 15-20% alcohol before the yeast dies off. Distillation is what gets you beyond that ceiling.
How Distillation Actually Works
The starting material is always something that has already been fermented: a beer-like grain wash, a wine, a fermented sugarcane juice, or a mashed fruit. This liquid, called the “wash” or “mash,” typically sits somewhere between 5% and 15% alcohol. The distiller heats it in a sealed vessel called a still, and as the temperature climbs past 78°C, ethanol begins to evaporate faster than water does. The vapor rises through the still, travels into a cooling apparatus (the condenser), and drips out the other end as a concentrated liquid.
It’s not a perfect separation. Water vapor comes along for the ride, and so do dozens of other chemical compounds produced during fermentation. A single pass through a simple still might bring the alcohol content up to around 30-50%. Multiple distillations, or more sophisticated equipment, can push it much higher. Vodka, for instance, is often distilled to 95% alcohol or above before being diluted back down with water.
Heads, Hearts, and Tails
Not everything that comes out of a still is safe or desirable to drink. The liquid that flows out changes character over the course of a distillation run, and distillers divide this output into three portions called “cuts.”
The first liquid to emerge is called the “heads” or “foreshots.” These contain the most volatile compounds, the ones with the lowest boiling points. Acetaldehyde, a major contributor to severe hangovers, boils at just 20.8°C. Methanol, the toxic alcohol that can cause blindness and death, boils at 64.7°C. Acetone comes through at 56.2°C. The heads smell harsh and solvent-like, and experienced distillers discard them entirely.
The middle portion is the “hearts,” and this is what becomes your drinking spirit. It’s predominantly ethanol with trace amounts of flavor compounds that give a spirit its character. Knowing exactly when to switch from collecting heads to collecting hearts is one of the core skills in distilling. There’s no universal temperature marker for the transition. Distillers rely on smell, taste, and experience to judge the right moment.
The final portion, the “tails” or “faints,” contains heavier compounds with higher boiling points. These include fusel oils, a group of bitter-tasting alcohols like butanol (boiling point 118°C) and amyl alcohol (131.6°C), along with acetic acid, the compound that gives vinegar its sour smell. Tails make a spirit taste oily and unpleasant. Distillers either discard them or recycle them into the next batch.
Pot Stills vs. Column Stills
The two main types of still produce noticeably different spirits. A pot still is the older, simpler design: a large copper pot with a wide base that tapers into a narrow neck. It works in batches. You fill it, heat it, collect the distillate, empty it, and start over. This is inefficient, but pot stills preserve more of the flavor compounds from the original fermented liquid, which is why they produce richer, more aromatic spirits. Single malt Scotch and cognac are legally required to be made in pot stills. Tequila, mezcal, and many Jamaican rums also rely on them.
Column stills, developed in the early 1830s, are tall cylindrical towers that operate continuously rather than in batches. Steam rises through perforated plates inside the column while the wash flows downward, creating repeated cycles of evaporation and condensation at different levels. This design can distill alcohol to a much higher purity in a single pass and separates heads, hearts, and tails more automatically. Column stills dominate the production of vodka, gin, and other lighter spirits. But the distinction isn’t absolute. Most bourbon and rye whiskey comes from column stills and still carries plenty of flavor and complexity.
Measuring Alcohol Strength
The alcohol content of a distilled spirit is measured as alcohol by volume (ABV) or as “proof,” which in the United States is simply double the ABV. An 80-proof bourbon is 40% alcohol. A 100-proof spirit is 50%.
Distillers measure strength using a hydrometer, a weighted glass instrument that floats at different levels depending on the density of the liquid. Alcohol is less dense than water, so a higher-alcohol liquid lets the hydrometer sink further. The U.S. federal gauging system calibrates these readings at 60°F. At any other temperature, the density of the liquid changes enough to throw off the reading, so distillers apply temperature correction factors to get an accurate proof. If the spirit contains dissolved sugars or solids, a standard hydrometer reading gives only an “apparent proof” rather than the true one.
The Methanol Question
Methanol is the safety concern most people have heard about, and for good reason. It’s toxic even in small amounts and has caused mass poisoning events throughout history, almost always involving illicit or poorly made spirits. But the risk is widely misunderstood.
Methanol forms naturally during fermentation, especially when fruit is involved. Commercially produced spirits contain it in small amounts that are not harmful. The WHO considers concentrations of 10 to 220 milligrams per liter in spirits to be within a safe, typical range. The European Union sets a legal limit for methanol in fruit spirits that provides roughly a fivefold safety margin even for heavy drinkers.
The danger arises when distillers don’t properly discard the heads, when methanol is deliberately added as an adulterant to cheap spirits, or when fermentation conditions aren’t controlled. Using cultured yeasts and maintaining an acidic pH during fermentation both reduce methanol formation at the source. In a properly run distillation with the foreshots discarded, the methanol that remains in the hearts fraction is well within safe levels.
Legal Status in the United States
In the U.S., you can legally brew beer or make wine at home for personal use. You cannot legally distill spirits at home under any circumstances. Federal law, enforced by the Alcohol and Tobacco Tax and Trade Bureau, strictly prohibits producing distilled spirits anywhere other than a TTB-qualified distilled spirits plant. Violations can result in federal criminal charges. This applies regardless of whether the spirits are for personal consumption or sale, and it applies even if your state has more permissive laws on the books. Some states allow ownership of a still for non-alcohol purposes like distilling water or essential oils, but actually running a fermented wash through it crosses the federal line.
A Brief History
Distillation of alcohol has roots stretching back at least two thousand years. Production of distilled spirits was reported in Britain even before the Roman conquest, though on a small scale. Spain, France, and the rest of western Europe likely practiced it earlier, but widespread production didn’t take off until the 8th century following contact with Arab scholars who had refined the technique. The earliest spirits were made from sugar-rich materials, primarily grapes (producing brandy) and honey (producing distilled mead). Using starchy grains as a base, the method behind whiskey and vodka, dates at least to the Middle Ages, though exactly when it started remains unclear.