How to brew it, and what to do when it goes wrong

The shape of the process

Home kombucha is four steps and one of them is waiting. Brew sweetened tea and cool it. Add the culture and its starter tea. Cover with cloth and leave it somewhere warm for one to two weeks. Bottle it, optionally with fruit, and leave the bottles sealed for a few days to carbonate.

That is the whole thing. Almost everything written about kombucha is an elaboration of one of those four steps, and almost every problem is a temperature problem, a starter tea problem, or a seal problem in disguise.

Why there are two fermentations

The first fermentation is open to the air, in a jar covered with cloth. The culture needs oxygen, and the carbon dioxide it produces simply escapes. This is where the sourness comes from.

The second is sealed, in a bottle, usually with a little fruit or juice for the yeast to work on. Now the gas cannot escape, so it dissolves into the liquid, and that is the fizz. Understanding this distinction resolves most confusion at once: a first fermentation is not supposed to be fizzy, and a second fermentation cannot happen in anything that is not sealed. Second fermentation is the full version.

The three things that actually go wrong

• It stalls. Almost always cold. A jar at 66 F can sit for three weeks and taste like sweet tea. Temperature is the fix.
• It will not carbonate. Almost always a seal, sometimes not enough sugar in the bottle, occasionally too cold again. Why kombucha is not carbonating runs the causes in order of likelihood.
• Something grew on top. Usually a new pellicle, sometimes yeast, rarely mold — and the three look nothing alike once you know what to look for. Mold versus SCOBY is the page to read before you throw a batch away.
• It went sour. Not a failure — a ferment that kept going past the day you wanted it to stop, and every cause is measurable. Why your kombucha tastes like vinegar runs them in order.

After the batch, and the questions people actually ask

Two things happen once a batch is bottled. It has to be stored, and somebody in the house asks what is in it. Storing kombucha covers why refrigeration is a brake rather than a preservative and what a sealed bottle left out actually does, while does kombucha have caffeine gives the published figures and is honest about where the research disagrees with itself.

And if the weekly brew-and-empty cycle stops suiting you, the method itself can change. How to run a continuous brew sets out the published proportions for a vessel you draw from and refill rather than empty.

Before you buy anything

Two questions come before the equipment. The first is whether the whole thing is worth doing — is brewing your own kombucha worth it works through what you buy once against what you buy repeatedly, and names the three cases where the honest answer is no. The second is what to put in the jar: the best tea for kombucha compares the bags on published gallons per pouch and lists the teas that will quietly starve a culture.

And one problem is common enough to deserve its own page rather than a paragraph. A fermenting jar gives off exactly the signals a fruit fly is looking for, which is why fruit flies and your kombucha jar covers the weave that actually stops them and what to do if they already got in.

And the method itself is not the only one worth knowing. Jun runs on green tea and honey rather than black tea and sugar, ferments cooler and finishes faster, which makes it the realistic ferment for a kitchen that never reaches kombucha's band — how to make jun covers the full method, including the one step that is genuinely different from brewing kombucha.

What is genuinely a safety question

Most kombucha worry is misplaced, and a couple of things are worth taking seriously. Acidity is the real defense, which is why pH testing earns its place. Fuzzy mold on the surface means the batch and the culture both go, with no exceptions. And every fermented drink produces a trace of alcohol, which matters for some households and not for others — kombucha alcohol content covers what is actually known.

We are not a medical source and we do not offer health advice. What this site can do is be exact about process and materials, cite what makers publish, and say plainly when something is not published. Home fermentation safety keeps to that line.

Water kefir has its own bottling stage and it behaves differently from kombucha's. The water kefir second ferment covers the pressure-rated bottles it needs, how much juice to add and why it finishes in a day or two rather than three to five.

And a batch does not have to end as a drink. Making kombucha vinegar on purpose covers the deliberate version of the thing most brewers only do by accident — the vessel, the timing, and the one figure you can never put on the result.

The other question that comes up once the routine is established is what happens when you stop. Leaving your kombucha while you are away covers the jar, the sealed bottles and the culture for a week, a month or a season — and why refrigerating the brewing jar is the instinct to resist.