How to Make Kombucha at Home

Before you start

Kombucha is sweetened tea fermented by a SCOBY, a rubbery mat of yeast and bacteria, together with a generous splash of mature kombucha from a previous batch. The yeast eat sugar and produce a little alcohol and carbon dioxide; the bacteria turn much of that into acids. After one to two weeks in an open jar under a breathable cloth, the sweet tea becomes tart, faintly fizzy and fruity. This page covers that first fermentation only.

Two things keep a home batch on the right track: acidity from the start and a clean, steady environment. The starter liquid lowers the pH of the fresh sweet tea immediately, which is what discourages mold and unwanted microbes, so never skimp on it. Keep the jar out of direct sun at a warm room temperature, use glass rather than metal, and taste regularly. For more bubbles, mix the finished kombucha with soda water when serving rather than sealing it in bottles, which can build dangerous pressure.

Ingredients

• 2 liters (8½ cups) filtered or dechlorinated water — divided
• 8 g (about 4 tea bags) black or green tea — plain tea with no added oils or flavorings
• 100 g (½ cup) granulated white sugar
• 250 ml (1 cup) unflavored mature kombucha — from a previous batch or a plain raw store-bought bottle
• 1 SCOBY — about the size of your palm or larger

Method

1. Wash the jar, spoon and your hands well with hot soapy water and rinse thoroughly so no soap residue remains. Avoid antibacterial soaps and do not use metal or decorative ceramic containers, which can react with the acidic liquid.
2. Bring 500 ml of the water to a boil, remove from the heat and add the tea. Steep for 5 to 7 minutes, then remove the tea bags or strain out the leaves.
3. Stir the sugar into the hot tea until completely dissolved. Add the remaining 1.5 liters of cool water and let the sweet tea cool to room temperature, below 30°C (86°F). Hot tea will damage the culture.
4. Pour the cooled sweet tea into the jar. Add the starter kombucha and stir. If you have pH strips, the mixture should read 4.5 or lower; if it does not, add more starter.
5. Slide the SCOBY onto the surface with clean hands. It may float, sink or sit sideways; all are normal.
6. Cover the mouth of the jar with the cloth or filter and secure it with a rubber band so fruit flies cannot get in. Set the jar somewhere at 21 to 27°C (70 to 80°F), out of direct sunlight and away from other ferments.
7. Leave it undisturbed for 7 days, then start tasting. Draw a little out with a straw or clean spoon from beside the SCOBY. It is ready when it tastes pleasantly tart with some remaining sweetness, like a sharp cider.
8. Lift out the SCOBY and set it in a clean bowl with 250 ml of the finished kombucha to use as the starter for your next batch. Pour the rest into clean jars and refrigerate.

Tips for success

• A new SCOBY layer usually forms on top as a thin, translucent film within a few days. Brown stringy bits hanging below it are yeast and are normal.
• Cooler rooms slow fermentation a lot. At around 20°C (68°F) a batch may need two weeks or more; warmer than about 29°C (85°F) can favor off flavors.
• Keep notes of the date, temperature and the day you liked the taste. Your own kitchen sets the timing more than any recipe does.

Substitutions

Black tea

Green tea makes a lighter, more floral kombucha and may ferment a little faster. Mixing half black and half green is a good middle ground. Avoid teas with added oils such as Earl Grey for the main brew, since oils can harm the culture.

White sugar

Organic cane sugar works the same way. Honey, maple and artificial sweeteners are not reliable substitutes: the culture is adapted to sucrose, and sugar-free sweeteners give it nothing to ferment.

Homemade starter

Plain, unflavored raw kombucha from a store can serve as starter. Pasteurized kombucha will not work because its culture is no longer alive.

Variations

Kombucha spritz

Fill a glass with ice, add 120 ml of chilled kombucha and 60 ml of fruit juice, and top with 60 ml of soda water for fizz without bottling.

Jun-style brew

Use green tea and swap the sugar for honey only if you have a SCOBY already adapted to honey; a regular SCOBY can struggle with it.

Troubleshooting

Fuzzy, dry spots appear on the surface

Raised, powdery patches of blue, green, black or white are mold. Discard the liquid and the SCOBY, clean the jar thoroughly and start again with more starter so the tea is acidic from day one.

After two weeks it still tastes sweet

The room is too cold or the starter was weak. Move the jar somewhere warmer and add another 100 ml of mature kombucha.

It smells strongly of vinegar

It fermented too long. Use it as a strong starter or a salad vinegar, and taste the next batch a few days earlier.

There is no new SCOBY layer

Cold, a disturbed jar or weak starter can slow film growth. If the liquid tastes tart and smells clean, the batch is still fine.

Storage

Refrigerate finished kombucha in clean glass jars with lids. Cold slows fermentation, but it continues gently, so drink it within about 2 weeks. Keep a SCOBY in some of its own kombucha at room temperature, covered with cloth, between batches.

Safety notes

Homemade kombucha contains caffeine from the tea and a small amount of alcohol from fermentation, which can rise with longer fermentation. Discard any batch with fuzzy mold or an off, rotten smell. People who are pregnant, immunocompromised or managing a health condition should check with a doctor before drinking it.