How a Moonshine Still Works (Explained Simply, With Diagram)

A moonshine still works by heating a fermented liquid in a pot until the alcohol turns to vapor, then cooling that vapor in a copper coil so it turns back into liquid and drips into a jar. That is the whole idea behind how a moonshine still works. Alcohol boils at a lower temperature than water, so you can separate the two with heat and cooling.

Below is a labeled moonshine still diagram. Follow it from start to finish: heat source, pot, cap, lyne arm, thumper keg, worm in the condenser tub, and collection jar. We'll walk through each part in that order. Then we'll explain how a copper pot still differs from other designs and why copper matters so much.

How Does a Moonshine Still Work? The Simple Science

Every still runs on one simple fact: different liquids boil at different temperatures. Ethanol, the alcohol in drinks, boils at about 173°F (78°C). Water boils at 212°F (100°C). When you heat a mix of the two, the alcohol turns to vapor sooner and in larger amounts than the water does.

A still catches that alcohol-rich vapor, moves it away from the pot, and cools it until it becomes liquid again. What comes out is much stronger than what went in. The starting liquid is called a wash or mash. It is a fermented liquid, usually about as strong as beer.

That's the whole chain: heat, vapor, cooling, collection. Each part of a still does one job in that chain. It's the same process early alchemists used to purify water and pull oils from plants, and once you understand it, you're thinking like one.

• Heat turns alcohol in the wash into vapor.
• The vapor rises and travels through a copper pipe.
• Cold water around a copper coil turns the vapor back into liquid.
• The liquid drips out into a jar.

Moonshine Still Diagram: Each Part, Step by Step

Here is what each labeled part on the moonshine still diagram does, in the order the vapor travels. Every copper moonshine still diagram you'll see follows this same basic path, even if the shapes look a little different.

• Heat source: A propane burner or electric heating element warms the pot from below. Steady, controllable heat matters more than high heat.
• Pot (boiler): The large copper tank that holds the wash. As it heats, alcohol vapor rises off the liquid.
• Cap / onion head: The rounded top that sits on the pot. It gives vapor room to rise and lets foam and heavy splashes fall back down.
• Lyne arm: The pipe leading out of the cap. It carries vapor sideways toward the next part.
• Thumper keg: A second, smaller copper tank. Hot vapor bubbles through liquid inside it, re-boils that liquid, and sends out stronger vapor. It's named for the thumping sound it makes.
• Worm (coil) in condenser tub: A coiled copper tube sitting in a tub of cold water. The water pulls heat out of the vapor so it turns back into liquid.
• Collection jar: The finished liquid, called distillate, drips out the bottom of the worm into a glass jar.

What Happens Inside the Pot and Cap?

The pot does the heavy lifting. As the wash warms up, nothing much happens at first. Once the liquid nears the boiling point of alcohol, vapor starts to rise. The temperature then keeps creeping up during the run, because the liquid left in the pot holds more and more water as the alcohol leaves.

The cap, often shaped like an onion, sits on top of the pot. It collects the rising vapor and funnels it into the lyne arm. Its size and shape give some vapor a chance to cool and drip back down, which helps keep watery splashes out of the line.

Even heat is the secret to a good pot. Hot spots can scorch the wash and add burnt flavors. Thick copper spreads heat evenly, and our patented Flame Flow™ stills (U.S. Patent 10,561,960) are built for faster heat-up, even temperature, less wasted propane and less scorching.

What Does the Thumper Keg Do?

The thumper keg is like a small bonus still in the middle of the line. Vapor from the lyne arm enters through a pipe that reaches down below the liquid inside the thumper. The hot vapor then bubbles up through that liquid.

As it bubbles, some of the vapor condenses, and its heat warms the thumper's liquid. Once that liquid gets hot enough, alcohol boils off it and moves on toward the condenser. The result is a second distillation in a single run, so the output comes out stronger than a pot alone would give.

The thump you hear is vapor pushing through the liquid in bursts. Traditional distillers sometimes added fruit or extra wash to the thumper for flavor. Our complete stills come with a thumper included. To learn what to put in it and what size you need, read our guide to the thumper keg.

How Does the Worm Condenser Work, and What Comes Out?

Vapor won't turn back into liquid until it loses heat. The worm is a long copper tube coiled inside a tub of cold water. Coiling packs a lot of tube into a small space, so the vapor touches plenty of cool copper on its way down.

Copper moves heat very quickly, so the vapor cools fast and condenses. The tub water warms up as it soaks up that heat. On longer runs, add cold water or keep it flowing so the bottom of the worm stays cool. If the distillate comes out warm, or you see vapor at the outlet, the water is too hot.

The distillate comes out as a thin stream or steady drip. Collect it in several small glass jars instead of one big container, because what comes out changes during the run. Distillers sort the output into four parts, called cuts:

• Foreshots: The very first liquid out. It holds the most volatile compounds, including acetone and methanol (which boils at about 148°F / 64°C). Always thrown away.
• Heads: Next up. Harsh, with a solvent or nail-polish smell.
• Hearts: The clean, smooth middle of the run. This is the part that's kept.
• Tails: The end of the run. Weaker, oily and heavy, with a wet-cardboard smell.

How Does a Copper Pot Still Work Compared to Other Stills?

A copper pot still works in batches. You fill the pot, run it until most of the alcohol is gone, then empty and refill it. The vapor rises and leaves with very little in the way, so much of the flavor from the grain or fruit carries over into the jar. That's why pot stills are the traditional choice for whiskey, rum, brandy and classic moonshine.

A reflux still adds a tall column that forces the vapor to condense and re-boil many times before it leaves. That makes a stronger, cleaner, more neutral spirit, but it also strips out flavor. A pot still with a thumper sits in between. You get more strength than a plain pot while keeping the character of the wash.

For a deeper side-by-side, see pot still vs reflux still. When you're ready to shop, browse our copper pot stills.

How Does a Copper Still Work, and Why Use Copper?

A copper still works the same way as any still, but copper adds two big advantages. First, it moves heat extremely well, so the pot heats evenly and the worm cools vapor fast. Second, copper reacts with sulfur compounds that yeast makes during fermentation. Those compounds smell like rotten eggs or burnt rubber. Copper binds with them, so less of that smell ends up in your jar.

Thickness matters too. Thin copper dents, warps and heats unevenly. Our stills are built from thick 20 oz, 22 gauge American copper, much heavier than the thin copper on cheap imported stills. Every seam uses lead-free silver solder. Each still is cut, rolled, formed, soldered, tested, adjusted and inspected at Fort Wilkins in Pittsfield, New Hampshire, and backed by a lifetime warranty. Learn more in what thickness copper for a still.

I build every still at Fort Wilkins to be handed down, not thrown out. — Alchemist G.G. Wilkins

If you want everything in the diagram in one box, our moonshine still kits complete with thumper include the pot, thumper and worm condenser.

Is It Legal to Use a Moonshine Still, and How Do You Run One Safely?

Under US federal law, it is legal to buy and own a still of any size. You can use it for distilled water, essential oils and similar non-alcohol uses. Distilling alcohol (spirits) at home for drinking is not legal without a federal permit from the TTB, even for personal use. A free TTB fuel alcohol permit allows you to make ethanol for fuel. State and local laws vary and can be stricter, so check yours. We don't give legal advice, but our article are stills legal to own? covers the basics.

Whatever you distill, a still uses heat and hot vapor, so safety comes first.

• Never seal the system. A still must stay open to the air at the outlet so pressure can't build up.
• Run propane burners outdoors or in a space with plenty of fresh air.
• Never leave a running still alone.
• Keep the condenser water cold so no vapor escapes. Alcohol vapor is flammable.
• Keep open flames and sparks away from the collection jar.