How to Make Kombucha at Home: The Method and the Safety

Making kombucha at home is genuinely easy, but it is a fermentation, so it rewards a bit of care. Get the ratio and the hygiene right and you get tangy, fizzy tea for a fraction of the shop price. Get them wrong and you get, at best, a bad batch, so the safety rules below are not optional. Here is the whole process.

What you need

• A SCOBY (the culture) plus starter liquid (mature kombucha from a previous batch or a trusted source)
• Tea: black or green, plain, no flavourings or oils
• White sugar: yes, real sugar; the culture eats most of it
• A large glass jar (never metal or lead-glazed ceramic; the acids react)
• A breathable cover: a tight-woven cloth and a rubber band, not a sealed lid

The ratio

A reliable starting ratio per 1 litre of water:

• 1 litre water
• 50g sugar (about 4 tablespoons)
• 2 teaspoons loose tea (or 2 bags)
• 100 to 200ml starter liquid per litre

The first ferment

1. Brew sweet tea. Steep the tea in just-boiled water, stir in the sugar to dissolve, and let it cool completely to room temperature. Hot tea will kill the SCOBY, so this step is not optional.
2. Combine. Pour the cooled sweet tea into the glass jar, add the starter liquid, then gently add the SCOBY.
3. Cover with the cloth and band so it can breathe but keep insects out.
4. Ferment 7 to 14 days at room temperature, out of direct sun. Taste from day 7: when it is pleasantly tangy and no longer too sweet, it is done. Warmer rooms ferment faster.

The second ferment (for fizz)

Optional but worth it. Bottle the kombucha in sealed bottles with a little fruit or juice, leave at room temperature 2 to 4 days to build carbonation, then refrigerate. The sealed bottle traps the CO2, which is what makes it fizzy. Refrigerate to stop fermentation once it is fizzy enough.

The safety rules (not optional)

• Glass only. Acids react with metal and can leach from lead-glazed ceramic. Use glass for fermenting.
• Cool the tea fully before adding the SCOBY. Heat kills the culture.
• Keep everything clean. Wash hands and equipment; contamination is the main risk.
• Watch the acidity. A healthy ferment turns acidic (below about pH 4.2), which protects it from harmful microbes. Adding enough starter liquid gets it acidic quickly.
• Mould means throw it out. Fuzzy spots (white, green or black) on the surface mean the batch is contaminated. Discard the whole batch and the SCOBY. Do not try to save it. The SCOBY itself is normally pale, rubbery and smooth; brown stringy bits hanging from it are normal yeast, not mould.
• Do not over-ferment in sealed bottles, which can build enough pressure to crack glass. Refrigerate once fizzy, and “burp” bottles if unsure.

A note on sugar, caffeine and alcohol

Do not skip the sugar; it is the fuel the culture eats, and most of it is gone by the end. The finished drink still contains some residual sugar, caffeine from the tea, and a trace of alcohol, which can run a little higher in home brews than in the commercial versions. The full picture is in what is kombucha.

FAQ

What do I need to make kombucha?

A SCOBY and starter liquid, plain black or green tea, white sugar, a glass jar, and a breathable cloth cover. No metal or lead-glazed containers.

How long does kombucha take to ferment?

7 to 14 days for the first ferment, tasting from day 7. An optional second ferment of 2 to 4 days in sealed bottles builds the fizz.

Why does my kombucha have no fizz?

Carbonation comes from a sealed second ferment. Bottle it with a little fruit or juice and leave it sealed at room temperature for a few days before refrigerating.

How do I know if kombucha has gone bad?

Fuzzy mould spots (white, green or black) on the surface mean throw the whole batch out. Brown stringy strands hanging from the SCOBY are normal yeast.

Can I use flavoured tea?

No. Teas with oils or flavourings can harm the SCOBY. Use plain black or green tea, and add flavour in the second ferment with fruit.

Recipe values are approximate. Ferment at your own discretion and follow the safety rules.