Kombucha brewing
CostLow to Medium
Includes: SCOBY, large jar and swing-top bottles up front, then very low per litre Example: Initial setup 20-40, under 1 per litre ongoing
What it is
Sweet tea, deliberately soured by a living pancake of bacteria and yeast, is the whole of it. That description sounds off-putting and the drink is genuinely delicious, which is the contradiction at the heart of why so many people brew it.
Kombucha brewing is the practice of fermenting sweetened tea with a SCOBY, a Symbiotic Culture Of Bacteria and Yeast, to produce a tangy, fizzy, lightly acidic drink. The SCOBY floats on the surface and converts the sugar and tea into acids, a small amount of alcohol, and carbon dioxide over one to two weeks. What you end up with is far less sweet than where you started.
The first ferment happens in an open jar covered with cloth, letting the culture breathe while keeping insects out. Black or green tea provides the nitrogen and tannins the SCOBY needs, and white sugar feeds it, around 70 grams per litre. Most of that sugar is consumed during fermentation, so the finished drink is not as sweet as the recipe suggests.
The second ferment is where it gets interesting. Bottled with a little fruit or juice and sealed, the kombucha builds natural carbonation and flavour over a few days. This is the stage where ginger, berries, or citrus turn a vinegary base into something genuinely refreshing. Most people find their first batch too sour, then learn to taste daily and bottle at the point they like.
The honest trade-offs are real. The SCOBY needs a warm, stable spot and looks alarming to the uninitiated, and a forgotten bottle can over-carbonate dramatically. But a litre costs cents to brew against €3 or more in shops, and most people who get the rhythm never stop.
How it works
The most common beginner error is starting without a healthy SCOBY and decent starter liquid, which leaves the brew open to mould. You need both: the rubbery culture disc and at least a cup of strong, already-fermented kombucha to acidify the batch and protect it while the culture gets going.
Brew a litre of strong tea, black or green, and dissolve in about 70g of sugar while it is hot. Let it cool to room temperature completely, because hot tea will kill the culture on contact. Pour it into a wide glass jar, add the starter liquid, then slide in the SCOBY. Cover with a tightly woven cloth and a band, never a solid lid, since the culture needs airflow but not fruit flies.
Leave it somewhere warm and dark, around 20 to 26°C, for seven to fourteen days. A new baby SCOBY forms across the surface as it ferments, which is normal and a good sign. Taste from day seven using a straw dipped past the culture. It should move from sweet toward pleasantly tart.
When the balance suits you, bottle it. A second ferment with fruit or ginger in a sealed bottle for a few days builds the fizz.
Benefits
What you need
Here's what to gather before you start. The essentials are marked.
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FAQs
A SCOBY, some starter tea, plain black or green tea, sugar, and a large glass jar. The SCOBY is the rubbery culture disc that does the fermenting, and you get it from another brewer or buy one online for around €10-15 with starter liquid. Avoid metal containers and utensils, which the acidity reacts with. A breathable cloth cover and a rubber band finish the kit.
Roughly 1 cup of sugar and 8 tea bags (or 2 tablespoons loose) per 4 litres of water, plus 1-2 cups of starter tea from a previous batch. The sugar feeds the culture, not you, since most of it gets consumed during fermentation, so don't reduce it thinking it'll be too sweet. Use plain tea only, because flavoured and oily teas like Earl Grey can harm the SCOBY over time.
7 to 14 days for the first ferment, depending on temperature. I start tasting around day seven: it should be pleasantly tart with just a hint of sweetness left. Too sweet means give it longer, too vinegary means you waited too long. Warmth speeds it up, so a batch in summer can be done in a week while winter might need two.
Almost certainly not, that's normal. Brown stringy bits are yeast strands, and a new pale layer forming on top is a baby SCOBY, both of which are signs of a healthy brew. Real mould is fuzzy and grows on top, in blue, green, or black patches like mould on bread. If you ever see that fuzzy growth, discard the whole batch and SCOBY and start fresh.
A sealed second ferment. After straining off the SCOBY, bottle the kombucha in airtight swing-top bottles with a little fruit or juice, then leave at room temperature for 2-5 days. The sugar in the fruit feeds the remaining yeast and builds carbonation in the sealed bottle. Burp the bottles daily to release pressure, then refrigerate to stop it once it's fizzy enough.
It's safe when made cleanly and kept acidic, which is its main defence against contamination. Always wash hands and equipment, keep metal away, and trust the smell-and-look test for mould. Kombucha does contain a small amount of alcohol from fermentation, usually under 1%, though a long second ferment raises it slightly. People who avoid alcohol entirely or are pregnant should be aware of that trace amount.
⚠️ Discard any batch showing fuzzy mould (blue, green, black) rather than trying to salvage it.
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