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What is Distillation?
Distillation separates chemicals by taking advantage of differences in boiling temperatures. Moonshiners make high proof alcohol by using distillation to separate alcohol from water. Note, distillation does not produce alcohol; it only concentrates the alcohol that is already present.
Distillation is actually the last step in the process of making moonshine. In the first part of the process, moonshiners essentially make a low proof beer, which gets distilled later. Here are all of the steps one needs to complete in order to make their own moonshine:
Make a mash using grains (such as corn) or sugar.
Ferment the mash by adding yeast.
Distill the fermented wash.
How Does Distillation Work?
The alcohol that moonshiners are after is called ethanol. It is able to be separated from water in a wash because ethanol boils at a lower temperature than water (pure ethanol boils at 172 degrees Fahrenheit, while water does not boil until 212 degrees). In a nutshell, wash is heated up in a still to a temperature above 172 degrees, but below 212 degrees. Ethanol starts to boil and turns into a vapor, separating from the wash water. The vapor is then condensed (turned back into a liquid) and drips out of the still into a mason jar or some other collection vessel.
The overall process of distillation is pretty cut and dry, but it is complicated slightly by the fact that there are several different types of alcohol (as well as many additional chemical compounds) that will be extracted during the distilling process. These are known as congeners (remember this word, it will come up again) and some are desirable in small quantities, while others (such as the foreshots) are not. Like ethanol and water, these compounds have different boiling temperatures.
When making vodka, as many congers are removed as possible because it is supposed to be a very pure, flavorless spirit. When making whiskey, the congeners are desirable because they add flavor and complexity. One of the reasons whiskey is aged is to smooth out the flavorful, but somewhat harsh cogeners present in the final product.
Phases of Distillation
Because the various alcohols and chemical compounds in a wash separate at different boiling temperatures, there are several phases of each distillation run: foreshots, heads, hearts, and tails. During the different phases of a run, taste and smell may vary considerably. Generally, only the "hearts" portion is kept for drinking. The tails are set aside to be distilled again in the future.
The foreshots are the first vapors to boil off during distillation. These contain the most volatile alcohols and should not be ingested, as they contain methanol and other undesirables. Moonshiners always discard the foreshots and never consume them. This portion makes up roughly 5% or less of all liquid collected during a distillation run. For more info on foreshots, read this article on moonshine blindness.
The heads contain "lighter" compounds such as Acetone, Acetaldehyde, and Acetate. These compounds taste bad and they smell like solvent. Additionally they are said to be the primary culprits in causing hangovers. There is little to no sweetness in this part of the run and it is far from smooth. The heads are not worth keeping for drinking and should be set aside. In general, roughly 20-30% of the liquid collected during a distillation run will be heads.
The hearts primarily contain ethanol and it is the most desirable part of the spirit run. One can tell when a still starts producing hearts because the harshness of the heads has dissipated and the smell is no longer harsh. This is the “sweet spot," which isn't just a metaphor. The whiskey produced during this phase is very flavorful, but also very smooth and, (depending on the recipe) slightly sweet. It is by far best tasting alcohol produced during a spirit run. The skill of the distiller comes into play as they must recognize the beginning and the end of the hearts portion of the run. However, in general, this phase will make up around 30-40% of all spirits collected during the entire distillation process.
The tails start once alcohols with lower boiling points has all evaporated. This portion of the run contains fusel oils such as propanol, butanol, and amyl alcohols. The tails are not very good tasting and are mostly water, proteins, carbohydrates and less volatile alcohols with higher boiling points. There are several ways that one can tell when heads end and tails begin. First, the flavor profile of the distillate will change significantly. The rich flavors present during the hearts will start to fade, as will the sweetness. Spirits collected during this phase will taste somewhat "thin." Additionally, the fusel compounds will create an ever so slight oily sheen on top of the distillate, which can be viewed at an angle in the right light (just as gasoline can be seen floating on top of water). The distillate will also be slightly slippery to the touch when rubbed together between a finger and a thumb. Tails make up the final 20-30 percent of liquid collected during a spirit run.
When to Stop Distilling
Experienced moonshiners generally run their stills until the alcohol from the wash has reduced to somewhere around 10-20 proof. It is not worth the time and energy to distill further to separate the little remaining alcohol from the water.
Making Distillation Cuts
An experienced distiller knows when to make a "cut" from the heads to the hearts and also from the hearts to the tails. In distilling a "cut" is when you stop collecting in one jar and start collecting in a new jar. This is a skill that is learned over time and required a bit of practice.
If the spirits will be aged, often times a small percentage of the heads and tails will be kept, along with all of the hearts, and added to the barrel. These cogeners, along with flavors extracted from the wood, provide the flavor and body of the final product.
Cuts can have a dramatic impact on the final product. Commercial distillers will tell you that It is best to make the head cut late and collect a bit of the hearts with the heads than to make the cut early and have heads mix with your hearts. Along the same note, it is better to make tails cut early and have a bit of hearts in the tails than vise versa.
The tails that have been saved from a run and kept for future use are called feints. Distillers sometimes add them to the wash of the next distillation run or they'll collect enough to make an all feints run, which is called "the queens share" by some folks.