Still construction is the design and building of the equipment that separates liquids by boiling point: a vessel to heat the liquid, a path for the vapour, and a condenser to bring it back.
It's a simple machine, and the simplicity is deceptive, because every one of its failure modes is either a fire or a pressure vessel.
A simple machine that punishes improvisation
There are three parts: something to hold and heat the liquid, something to carry the vapour, and something to cool it back to liquid. That's it, and people have built working stills from scrap for centuries.
The simplicity is what makes it dangerous. Almost anything can be made to produce a distillate, and the things that separate a safe still from an unsafe one, the materials, the vapour path, the heat source, the ventilation, are not visible in the output. A badly built still works right up until it doesn't.
So this subject is mostly about the decisions instead of the assembly: what it's made of, how heat gets in, where vapour can and cannot go, and how you'd know if something was wrong. Those are the parts worth understanding, and they're the parts most improvised builds skip.
01
The three parts, and what each does
The boiler holds the liquid and receives the heat. Its size sets the batch, its material decides what ends up in the product, and its lid has to seal well enough to send vapour where you want it while never being able to trap pressure.
The vapour path carries what boils off to the condenser. Its length, its shape and whether anything is packed inside it decide how much separation happens on the way, which is the difference between a pot still and a reflux one.
The condenser turns vapour back to liquid, by giving it a cold surface and enough of it. Undersized condensers are the commonest design fault: vapour that isn't fully condensed leaves as vapour, which loses product and creates exactly the flammable atmosphere the caution warns about.
Everything else, thermometers, sight glasses, valves, is instrumentation. Useful, and none of it substitutes for the three parts being right.
02
Pot and reflux, and choosing between them
The two families differ in one thing: how much the vapour is made to condense and re-evaporate on its way out.
A pot still is the simple one. Vapour goes more or less directly to the condenser, separation is modest, and the distillate carries a great deal of the character of what it came from. That's a virtue for anything where flavour is the point and a limitation where purity is.
A reflux still deliberately makes some vapour condense and fall back, so the rising vapour is repeatedly re-separated on the way up. That's what a column packed with material does. The result is a much purer, higher-strength, more neutral distillate, which is what you want for fuel, for solvent and for antiseptic use.
The packing is the mechanism: it provides surface area for that repeated condensation and evaporation. Inert, clean, non-reactive material only, and it must never be able to compact or block the path.
03
Materials, which decide what ends up in the product
This is where an otherwise sound build goes wrong, because the wrong material is invisible in the result.
Copper is the traditional choice and it earns it. It conducts heat well, it's workable with hand tools, and it chemically removes certain sulphur compounds from the vapour, which genuinely improves the product. Its drawback is that it corrodes and needs cleaning.
Food-grade stainless steel is durable, inert and easy to clean, and it does none of the useful chemistry copper does. A common arrangement uses stainless for the boiler and copper somewhere in the vapour path, which gets both.
What must never be used: lead in any form, including old solder, which leaches into the product; galvanised or zinc-coated metal, which gives off fumes when heated; aluminium, which reacts; and plastics or rubber not rated for the temperature, which contaminate. Salvaged plumbing fittings are the usual source of the first of those, because old solder is frequently leaded and looks identical to the modern kind.
04
Getting heat in safely
The heat source is the single largest safety decision in the build, because it's the ignition source sitting next to the flammable vapour.
Direct flame under a boiler is traditional and is the riskiest arrangement, particularly indoors. If it's used at all it belongs outdoors or in a genuinely well-ventilated space, with the flame shielded from any possible leak path.
An internal electric element is efficient and removes the flame entirely, and it introduces its own requirement: it must be properly rated, properly sealed, and it must never be able to run dry, because an exposed element in vapour is an ignition source. Anything electric in this application needs to be done properly, not adapted.
A water or steam jacket heats indirectly and cannot scorch what's in the boiler, which matters for anything with solids in it. It's the gentlest method and the most work to build.
Whatever the source, the requirement is control. Being able to reduce heat quickly is what stops a run boiling over into the vapour path, and that carries liquid into the product and can block the path.
05
Running it, and knowing when to stop
Operation is where a good build is either used well or wasted.
Bring it up slowly. A fast start throws liquid into the vapour path, which fouls the product and is one of the ways paths get blocked. Steady, gentle heat produces a steady output, and a still that's surging is being pushed too hard.
Watch the temperature and the flow in place of the clock. The temperature at the top of the column tells you what's coming over, and it moves as the composition of the boiler changes. Output that suddenly changes rate or temperature is the still telling you something.
Never leave it running unattended. Nothing about this is compatible with being in another room, and most serious incidents involve a still that was left.
And stop cleanly. Cut the heat before the boiler runs low, let it cool before opening anything, and clean it after every run, because residue in a vapour path is how blockages start.
Pressure, relief and the discipline of designing so that a failure is safe instead of merely unlikely.
Where this subject stands
The library doesn't cover Still Construction yet. It's in planning, and what gets written next is impacted by what readers ask for.
Tell us what you want to distil and why, flavour, purity or fuel, and what materials you can actually source. Those decide the design before anything else does.
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Questions
What is the difference between a pot still and a reflux still?
How much separation happens on the way out. In a pot still the vapour goes more or less straight to the condenser, so the distillate carries much of the character of what it came from. A reflux still makes some vapour condense and fall back repeatedly, usually through a packed column, which separates far more thoroughly and gives a purer, stronger, more neutral product. Flavour wants the first; fuel, solvent and antiseptic use want the second.
Can I build a still from salvaged materials?
Partly, and this is where people get hurt. Copper and food-grade stainless are fine and frequently available second hand. What must be excluded is lead in any form, including old solder on salvaged plumbing, which looks identical to lead-free and leaches into the product; galvanised metal, which gives off fumes when heated; and aluminium, which reacts. If you cannot establish what a salvaged fitting is made of, do not use it in the wet or hot path.
Why does the vapour path have to be unobstructed?
Because a sealed heated vessel with nowhere for vapour to go is a pressure vessel with no relief, and it fails violently. Nothing that can plug, freeze or be closed belongs in that path, packing must not be able to compact, and the design should make blockage impossible and not unlikely. This is the single most important thing about building one.
Is a thermometer necessary?
Not for the still to work, and very useful for knowing what it's doing. The temperature at the top of the column indicates the composition of what's coming over, and it moves as the boiler changes, which is information you otherwise have to infer. It's instrumentation and not a safety device: it tells you what's happening and it doesn't prevent anything.
The Ark is a library of practical knowledge that was ordinary once and isn't any more, being recovered from the sources that recorded it while it was still in use. Membership is what pays for that work, and it's what decides how fast subjects like this one get written.