Hub 05 · Kombucha, Kefir & Yogurt
First-batch troubleshooting
The seven things that go wrong on a first cultured drink, what each one means, and which of them is the one you must not ignore.
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| Symptom | Likely cause | Fix |
|---|---|---|
| No fizz at all | You skipped the second ferment | Bottle it sealed with a little fruit or sugar for a few days |
| Nothing happening after a week | The room is too cold | Move it somewhere warmer; expect it to be slow, not dead |
| Far too sour | Left too long, or too warm | Ferment for less time next batch; use this one as vinegar |
| Still sweet after two weeks | Cold, or a weak culture | Warmth and time; check the starter liquid was included |
| Brown strands hanging down | Yeast — normal | Nothing |
| A bulging bottle or container | Pressure from active fermentation | Refrigerate, then open slowly over a sink |
| Fuzzy dry growth on the surface | Mold | Discard everything, including the liquid |
No fizz is the commonest disappointment
And it is almost always because there was no second ferment. An open, cloth-covered jar lets carbon dioxide escape by design, so the first ferment produces sour kombucha and not much else.
Bottle it in sealed swing-top bottles with a little fruit or juice, leave it a few days at room temperature, then refrigerate. That is where the fizz comes from.
Nothing happening is usually the thermometer’s fault
Cultured drinks are strongly temperature-dependent, and a January kitchen is colder than most instructions assume. A brew that is doing nothing after seven days in a cool room is generally slow rather than failed.
Move it somewhere warmer — the top of a fridge, a warm cupboard — and give it time before concluding anything.
Too sour is not a failure
Over-fermented kombucha is essentially vinegar, and it is perfectly usable as such. It also makes excellent starter liquid for the next batch, which needs acidity more than it needs to be pleasant.
Shorten the next ferment and start tasting earlier.
The bulging container, again
This is the only symptom on the chart with a real safety dimension, and it comes up as often with a jar of kimchi as with a kombucha bottle. Actively fermenting food in a sealed container builds pressure, and glass under pressure fails suddenly.
Prevention is straightforward: burp sealed bottles daily during a second ferment, refrigerate them once carbonated, and never leave one in a warm room and forget about it. For vegetables, use a lid that vents — see best fermentation lids.
When to throw it out
Fuzzy, dry growth sitting proud of the surface — blue, green, black or white and raised. Discard the culture and the liquid, and do not try to salvage the SCOBY underneath it. Everything else on this chart is recoverable.
If you are unsure, throw it out. A batch of tea is cheap. The full description of what healthy looks like is in what is a SCOBY.
Frequently asked
Questions
+Why is my kombucha not carbonated?
Because carbonation happens in the second ferment. The open first-ferment jar lets carbon dioxide escape. Bottle the finished kombucha in sealed swing-top bottles with a little fruit or sugar for a few days at room temperature.
+Why is my kimchi container bulging?
Active fermentation producing gas in a sealed container. Move it to the fridge to slow the ferment, then open it slowly over a sink with a towel over the lid. Use a lid that vents during active fermentation rather than a sealed one.
+My kombucha is too sour. Can I fix it?
Not this batch, but it is not wasted — over-fermented kombucha works as vinegar and makes excellent starter liquid for the next brew, which needs acidity more than flavor. Ferment for less time next round.
+How do I know if my brew has gone bad?
Fuzzy, dry growth raised above the surface means mold — discard the culture and the liquid. Brown stringy strands, cloudiness and an uneven culture surface are all normal. If you are unsure, throw it out.
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