Fermentation and distilling
Put microbes to work — your first biotechnology.
Also listed under Food & Agriculture › Storage and preservation, because that subject depends on it.
Everything for this step
- Field guide
- Food preservation → 7 sections Micro-organisms → 6 sections Essential medicines → 2 sections Poisons → 2 sections
- Builds
- Slow sand filter
- Reference sheets
- None.
- Sciences it rests on
- Microbiology · Chemistry
Why this matters
Fermentation preserves food, makes water safe, produces medicine and disinfectant, and is the first process where you are deliberately cultivating an organism rather than a plant. Distillation is more important still: it is the core operation of all chemistry, and once you can build a still you can separate almost anything.
The shape of it
- Start with lactic fermentation — vegetables in salt brine, excluded from air. It needs no starter culture, preserves vitamin C through winter, and is nearly impossible to get dangerously wrong.
- Then dairy: yoghurt and cheese, which turn milk that keeps for a day into food that keeps for months. See The Complete Book of Cheese.
- Then alcohol. Malt the grain (germinate and dry it) to convert starch to sugar, mash with hot water, then ferment. Weak beer was historically a safer drink than water — the boil during mashing is what actually makes it safe, not the alcohol.
- Then vinegar. Let alcohol go further and acetic bacteria produce vinegar: a preservative, a cleaner, a mild acid for chemistry, and the solvent for iron gall ink.
- Build a still. A copper pot, a head, and a condenser — a coiled tube in cold water. Ethanol boils at 78 °C, well below water, so gentle heat lifts alcohol first.
- Discard the first fraction. The heads carry methanol and other volatiles which cause blindness and death. This is not folklore — take it seriously and be conservative about how much you throw away.
- Concentrate for medicine, not for drinking. Alcohol above roughly 60% is a genuine antiseptic for skin and instruments, a solvent for plant medicines, and a preservative for specimens. That is worth more than the recreational use.
- Understand what you have built. A still is a fractional separator. The same apparatus, refined, gives you distilled water, essential oils, solvents, and eventually the acids that industrial chemistry runs on.
Doing it, step by step
The summary above says what has to happen. This says how, with the numbers that decide whether it works.
1 · Start with a lactic ferment — nearly impossible to get dangerously wrong
Shred vegetables, add 2–2.5% of their weight in salt, pack them under their own brine, weight them down, and hold at 18–22 °C for 3–6 weeks. The lactic bacteria already on the leaves drop the pH below 4, where spoilage organisms cannot grow. No starter, no equipment, and it preserves vitamin C through the winter.
The full procedure, including how to tell harmless yeast film from mould, is in preserving the harvest. Start here because it teaches the discipline every later ferment needs: clean vessels, measured salt, air excluded, temperature watched.
2 · Scald every vessel — the organism you culture is the one you let in
Fermenting in a dirty vessel cultures the wrong organism, and the failure shows as a sour, ropy, rotten or mouldy batch — or does not show at all. Scrub every vessel, then scald it with boiling water immediately before use. Wooden vessels are scalded and kept in use, since they harbour whatever lived in them last.
Keep one set of vessels per purpose — beer, vinegar, dairy — because vinegar bacteria in a beer vessel turn the next beer to vinegar.
3 · Malt, mash and ferment grain into beer
- Steep barley in water 24–48 hours, draining and airing it every 8–12 hours so it does not drown.
- Germinate it spread thin and turned, 4–6 days, until the shoot inside the grain is about three-quarters of the grain's length.
- Kiln-dry it gently, below about 50–60 °C — hotter kills the enzymes that convert starch.
- Crush and mash in water held at 63–68 °C for about an hour. The enzymes turn starch to sugar.
- Boil the strained liquid for an hour — this is what makes beer safe to drink, not the alcohol.
- Cool below 25 °C, add yeast, and ferment at about 18–22 °C for 1–2 weeks.
4 · Let alcohol go on to vinegar
A weak alcohol — beer or wine below about 8% — left open to air under a cloth, with a little mother of vinegar from a previous batch, warm at about 25–30 °C, turns to vinegar in weeks as acetic bacteria oxidise the alcohol.
Pickling needs vinegar of at least about 5% acidity. Without a way to measure, use vinegar from a reliable, fully fermented batch that has stopped smelling of alcohol, and keep home vinegar for cleaning and chemistry where strength matters less. Vinegar is also the solvent for iron gall ink.
5 · Build a still that cannot poison or explode
A copper or stainless pot, a head, and a condenser — a coiled tube in a tank of cold running water. Copper also removes sulphur compounds from the spirit.
- No lead solder, no galvanised (zinc-coated) metal, no plastic anywhere the vapour or spirit touches. Lead dissolves straight into the product.
- Never seal it. The condenser outlet stays open to the air. A blocked still is a boiler with no safety valve.
- Keep flame away from the output. Ethanol vapour is heavier than air and ignites; heat with a closed firebox or a water bath, and collect the spirit well away from the fire.
6 · Make the cuts, and throw the first fraction away
Heat gently. Ethanol boils at 78 °C, methanol at 65 °C, so the lightest compounds come first.
- Foreshots and heads — the first spirit, sharp and solvent-smelling. Carries methanol and other volatiles. Discard at least the first 100–150 ml per 20 litres of wash, and more from fruit mashes, which carry more methanol than grain.
- Hearts — clean-smelling spirit. Keep it.
- Tails — oily, wet-cardboard smell as the run weakens. Set aside to redistil.
Collect in small numbered jars so the cuts can be judged by smell afterwards rather than guessed at during the run.
7 · Concentrate for medicine, and measure the strength by weight
Alcohol at 60–80% by volume — ideally about 70% — is an antiseptic for skin and instruments. Pure alcohol works less well, because some water is needed to penetrate cells. Redistil hearts to raise the strength.
Measure by weighing exactly one litre at room temperature: water 1,000 g; 60% about 909 g; 70% about 886 g; 80% about 860 g. Dilute with boiled water to hit the target. Label every bottle with strength and date. It is also a solvent for plant medicines.
8 · Cap what brewing and distilling may take from the grain store
Letting alcohol consume grain the settlement needs to eat is the failure that matters most. A distillation run uses a great deal of grain for a small volume of spirit.
Set a written limit: brewing and distilling draw only from grain surplus to the year's food, seed and the one-third reserve — see staple crops. Record grain used per litre of spirit. The still's real value is as a fractional separator — distilled water, essential oils, solvents, and eventually the acids industrial chemistry runs on — not the drink.
Build it
Dimensioned drawings, bills of materials and construction procedures for the things this step asks for.