Heads, Hearts, and Tails: Why Cuts Exist

A stripping run is about speed and concentration. A finishing run is different: it’s where you separate fractions—and those fractions are where a lot of your flavor decisions live.

Quick summary

Finishing run and fractions

On a finishing run, you’re starting with a stronger boiler charge (for example, ~30% low wines). The vapor can be much higher (for example, ~60%–75%) early in the run, which helps you land an overall new make around ~60%–65% for barrel aging.

So distilling is about that pot, a riser, a bridge, and a cooler. We cool the vapors back down to liquids. And because the alcohol molecules are lighter, they are overrepresented.

If we distill too long, we continue distilling, we basically end up with an 11% concoction. So we want to stop after collecting around 1 3rd. So let's do the second run, which is the finishing run.

Remember how we looked at water molecules and alcohol molecules? And alcohol molecules boiling at a lower point, signifying it's easier to bring them to a gas state, resulting in the fact that the gases during distillation are always higher in alcohol percentage than the boiler they come from. Now we're going to fill that boiler again.

Alcohols aren’t just ethanol

Real distillate isn’t “water + ethanol.” Distillers talk about a family of alcohols and related compounds that behave differently during the run. Some are very low-boiling (they show up early), and some are high-boiling (they show up late, sometimes even above water’s boiling point).

The wine is now, for example, 30%, and we create gases that are 60, 70, 75%, depending on where we are in the process. We use the same little system to actually make sure that we create an overall brandy and new makes spirits of around 60, 65%, which is the goal for barrel aging. It extracts the right flavors, which you can read on Understanding Barrels.

Another topic that we talk about a bit later. First run is about concentrating the alcohol. The second run is about cutting, separating the alcohol.

Heads, hearts, and tails

Because low-boiling compounds enter vapor more easily, they’re overrepresented at the start of the finishing run (heads). After those are depleted, ethanol dominates (hearts). As ethanol declines, heavier, high-boiling compounds become more represented (tails).

I want you to understand that alcohol is a concoction of a family of alcohols. Starting with acetone, a ketone basically, but still considered part of the alcohol family by distillers. Acetone has a boiling point of around room temperature, which is why you immediately recognize the smell.

If you want to take the missus out for dinner and things are running late, she yells down like, I'm almost done, honey, I'm almost ready to leave. And you smell that smell of nail polish remover, you're in trouble and it will take another half an hour at least. You find it in wine, you find it in beer.

Two extremes in the cut debate

You’ll hear two loud opinions: (1) cut out as much heads and tails as possible for “health” and cleanliness, or (2) include everything to maximize yield and blame hangovers on overdrinking. Neither approach helps you design a flavor profile on purpose.

If you're going to make a whiskey vodka, you are going to have to deal with that very light molecule. Very light, very small, evaporates at room temperature, which is why you smell it all through the house, even though your wife isn't boiling the nail polish remover. She's just putting it on her hands, that's all.

There are alcohols that are very small, very light, have low boiling points, come into a gas phase very easily, very quickly, with limited amount of energy. And there's very heavy ones like furfural or propanol or butanol that are very, very heavy, have high boiling points, even higher than water sometimes. And they don't get into a gas phase easily, takes a lot of energy.

What’s next: a flavor model

Next, you’ll use a third way: choose cuts based on the flavors you want for a specific spirit style. Continue with Where flavor actually lives.

Just as with distilling water and alcohol, like on the first run, we see that a lighter alcohol is overrepresented in the beginning of the run. If we do the finishing run, we have to understand that the beginning of the run, we see a bleed off of very light alcohols. Acetones, methanol, ethyl acetate, officially not an alcohol, but let's compromise it or let's put it into the family here, because that's the way it's often looked at.

Boiling points that are lower than the 78 degrees of good ethanol. And because these are lighter molecules that make it to the gas phase sooner, without a lot of energy, they're overrepresented in the beginning of the run. Ethanol's the good alcohol, water ethanol, and the high boiling point, the heavy alcohols, the furfural, the propanol, and butanol.