I was sitting at the bar at the Rackhouse Tavern inside the Campbell House Hotel in Lexington, working through a bourbon flight, when the bartender set down an extra pour with a little smile that I probably should have read more carefully. A bonus, she said. On her.

It was Jeptha Creed. I’d heard of them — small Kentucky distillery, interesting backstory, doing things a little differently. I picked up the glass and took a sip.

It tasted like sweat socks.

I looked up. She was already grinning. She knew.

I don’t know exactly what went wrong with that pour. Could’ve been the distillate itself. Could’ve been the barrel — a bad stave, wrong char level, something funky in the wood. Could’ve been a fermentation issue that survived the still entirely. I genuinely don’t know, and I’m not going to pretend otherwise. But that little ambush in Lexington sent me down a rabbit hole about where off-flavors actually come from, and the biggest part of that answer lives in something called the cuts.

If you’ve ever tasted a bourbon and thought something was just a little off — too harsh, too solvent-y, or weirdly heavy and almost soapy — there’s a good chance you were tasting the consequences of where a distiller decided to make their cuts. Understanding what that means changes how you drink.

First, what’s actually happening in the still

Bourbon production starts with a fermented grain mash — corn-heavy by law, at least 51%, with malted barley and either rye or wheat rounding it out. If you want the full breakdown of what legally separates bourbon from every other whiskey on the shelf, I covered that here. For now, what matters is what happens after the fermentation is done.

That fermented mash goes through what’s called a stripping run, usually in a column still or a pot still depending on the distillery. The stripping run is exactly what it sounds like: you’re stripping the alcohol out of the wash, concentrating it, and producing what’s called low wine. It’s rough, broad, and not particularly pleasant on its own. Think of it as raw material.

The low wine then goes into a second still — the spirit still — for what’s called the spirit run. This is where distilling gets interesting. This is where the distiller actually earns their paycheck.

As the spirit run progresses, different compounds come over at different times. Not everything in that still is something you want in your glass. Some of it is great. Some of it will make you wish you’d ordered a beer. The distiller’s job is to know the difference, and to make a series of decisions — called cuts — about what to keep and what to discard.

Those decisions get divided into three parts: heads, hearts, and tails.

Heads: the stuff you absolutely don’t want

The heads come over first. They’re high in methanol and lighter alcohols like acetaldehyde and ethyl acetate, and they smell and taste exactly like you’d expect chemicals to smell and taste. Nail polish remover. Paint thinner. A harsh, almost eye-watering solvent burn that sits at the front of your palate and doesn’t do anything pleasant after that.

Every distiller discards the heads. That’s not a craft decision, that’s just the minimum standard for not making people sick. The question is where exactly you make the cut — how much of the transition zone between heads and hearts you’re willing to include, and how clean you want that opening to be. Cut too early and you’re switching to hearts collection before the heads have fully cleared, which means those solvent compounds ride right along into your spirit. Cut too late and the heads are gone, but you’ve thrown out good ethanol along with them — wasteful, but at least it doesn’t end up in the glass.

When you taste a young or poorly made whiskey and it hits you with that harsh, almost chemical heat right up front — that’s heads bleed. That’s the cut coming too early, before the distiller gave the heads enough time to clear.

Hearts: where everything you love about bourbon lives

The hearts are the reason you’re doing any of this. Once the heads have come over and the distillate starts to clean up, you hit the sweet spot — the ethanol-rich, flavor-rich middle of the run that contains all the good stuff. Fruit esters, floral notes, the early development of what will eventually become that caramel and vanilla character after years in oak.

A well-made bourbon’s heart cut is where the distiller’s real personality shows up. Some distillers run a wide hearts cut, pulling more of the transition zones on both ends to get more flavor complexity and body. Some run it tight and clean for a more precise, refined spirit. Neither approach is wrong. They’re just different philosophies, and you can taste them. The Wilderness Trail 10-Year Wheated Bourbon is a good example of what a clean, precise hearts cut looks like in the glass — soft, controlled, nothing out of place.

The hearts cut is a judgment call made in real time, by a human, based on smell and taste and experience. No algorithm is making that decision for you.

That’s what makes it interesting. This isn’t a process that runs on autopilot. The distiller is nosing the spirit as it comes off the still, tasting it, deciding. In a world where so much of what we consume has been optimized and automated into sameness, the hearts cut is a judgment call made in real time, by a human, based on smell and taste and experience. No algorithm is making that decision for you.

Tails: the complicated part

After the hearts come the tails, and this is where things get genuinely interesting from a flavor standpoint. The tails are heavier compounds — fusel alcohols, fatty acids, sulfur compounds — that come over later in the run as the alcohol content drops. They can smell musty, oily, almost meaty. At high concentrations, they’re unpleasant. That funky, heavy, almost sour quality that sometimes shows up in a pour you can’t quite put your finger on? Could be tails.

But here’s the thing: a little bit of tails isn’t always bad. Some distillers intentionally pull into the tails to add body, texture, and a kind of savory depth that a tight cut wouldn’t give you. Done right, it adds complexity. Done wrong — or if something else went sideways in the process — it tips over into that funky, off-putting territory that made me hand the glass back with a look that probably said everything.

The tails are where a distiller’s restraint gets tested. Anyone can make a clean, tight spirit. Knowing exactly how far into the tails you can reach before you’ve gone too far — that’s craft.

What about rye?

Rye whiskey runs through this same process, but the grain bill changes the character of everything that comes off the still. Rye is spicier, more aggressive, and produces a different flavor profile in the hearts — more pepper, more bite, more of that distinctive rye funk. The tails cut on a rye can be especially tricky because those heavier compounds interact differently with the spice character of the grain. A little too much tail on a rye and it can turn harsh in a way that’s harder to recover from than it would be with a softer corn-forward bourbon. The Old Hickory 12-Year Bottled-in-Bond Rye is a good recent example of what happens when a distiller gets the rye cuts right — long-aged, controlled, nothing fighting itself in the glass.

It’s part of why well-made rye is genuinely impressive when you find it.

Why any of this matters when you’re just trying to enjoy a drink

It matters because it changes what you’re tasting for. The next time a bourbon hits you with something harsh and chemical up front, you’ve got a name for it now. The next time a pour feels heavy and almost oily in a way that doesn’t quite work, you know where that’s coming from. And the next time you open something and it’s just clean and balanced and exactly right from the first sip to the finish, you’ll know that somewhere, at some point, a distiller made a very good call.

That bartender at the Rackhouse knew exactly what she was handing me. She was having a little fun, sure. But that pour — bad as it was — is probably the most educational drink I’ve ever had. Sometimes the worst glass teaches you the most about what a good one is supposed to be.

If you want more of this kind of breakdown — the craft, the process, what’s actually in the glass — the newsletter is where I send it first.