How to Make Kombucha at Home

A practical beginner’s guide to brewing fermented tea safely

The first time you make kombucha, the process can feel surprisingly uncertain. You prepare a large jar of sweet tea, place a strange rubbery disc on top and then leave it sitting on the kitchen counter for a week. Is it fermenting? Has it gone wrong? Is that brown string normal? And how are you supposed to know when it is ready?

Once you understand what is happening in the jar, kombucha becomes much simpler.

Kombucha is sweetened tea fermented by a community of yeasts and bacteria. The yeasts begin breaking down the sugar and produce, among other substances, small amounts of alcohol and carbon dioxide. Acetic-acid bacteria then convert part of that alcohol into organic acids. Gradually, the tea becomes less sweet, more acidic and sometimes lightly sparkling.

The familiar rubbery layer is often called the SCOBY, although technically it is the pellicle: a cellulose layer produced during fermentation. It contains microorganisms, but the fermented starter liquid is at least as important. That acidic liquid helps establish the right environment from the beginning.

This guide starts with a two-litre batch: large enough to be worthwhile, but still manageable while you learn how your kombucha behaves.

What you need

For approximately two litres:

• 1.75 litres water

• 100 g ordinary white sugar

• 10 g loose black or green tea, or approximately 5 tea bags

• 250 ml mature, unflavoured kombucha as starter liquid

• One healthy kombucha pellicle

• A clean glass jar of at least 2.5 litres

• A tightly woven clean cloth or paper coffee filter

• An elastic band

• A clean spoon

• Glass bottles suitable for carbonated drinks, if you want to bottle it later

For your first batch, obtain the pellicle and starter liquid from a reliable source. A commercially purchased starter is preferable to an unidentified culture that may have been stored or handled poorly.

Use real tea from Camellia sinensis, such as black, green, white or oolong tea. Herbal infusions do not contain the same nutrients and should not be used as the sole base while you are establishing a culture. Avoid flavoured teas containing essential oils, which may interfere with fermentation.

Getting started

Step 1: Clean your equipment

Wash your hands and clean the jar, spoon and any other equipment thoroughly. Rinse away all soap residue.

You do not need to turn your kitchen into a sterile laboratory. Kombucha is itself a living microbial culture. You do, however, want to avoid introducing food residue, mould spores or unwanted microorganisms.

Inspect the jar for cracks or damage. Glass is preferable because kombucha becomes acidic and prolonged contact with unsuitable metals, ceramics or plastics may cause unwanted substances to leach into the drink.

Step 2: Make the sweet tea

Bring the water to the boil. Add the tea and allow it to steep for approximately 10 minutes. Remove the tea leaves or bags, add the sugar and stir until it has completely dissolved.

The sugar is not simply added to make the drink sweet. It feeds the yeasts and bacteria responsible for fermentation. Trying to make “healthier” kombucha by sharply reducing the sugar can create a weak or unpredictable ferment. Some sugar will remain in the finished drink, but the amount depends on the culture, temperature and fermentation time.

Allow the sweet tea to cool completely to room temperature. Never add the culture to hot tea: heat may damage or kill the microorganisms you need.

Step 3: Add the starter

Pour the cooled tea into your glass jar. Add the 250 ml of mature kombucha and gently place the pellicle on top.

It may float, sink, turn sideways or hover somewhere in the middle. All of these are normal. A new cream-coloured layer will often begin forming at the surface, regardless of where the original one ends up.

The starter liquid acidifies the new batch and helps suppress undesirable organisms. Do not replace it with vinegar. Vinegar has a different microbial composition and may change the culture.

Step 4: Cover and ferment

Cover the jar with a tightly woven cloth or coffee filter and secure it with an elastic band. The covering must allow airflow while keeping out fruit flies and dust. Cheesecloth is often too loosely woven.

Place the jar somewhere:

• Out of direct sunlight

• Away from the cooker and strong odours

• Where it will not be repeatedly moved

• At a reasonably stable room temperature

Around 20–25°C generally works well. A cooler room slows fermentation; a warmer room accelerates it and may make the kombucha turn acidic more quickly.

Allow it to ferment for approximately 7–14 days.

Step 5: Begin tasting

Start tasting after about seven days. Slide a clean straw or spoon beneath the surface and remove a small amount without drinking directly from the utensil and returning it to the jar.

At first, the tea will still taste quite sweet. As fermentation progresses, the sweetness recedes and the acidity becomes more noticeable. It is ready when it tastes pleasantly tart but still balanced—not when a fixed number of days has passed.

Your kitchen temperature, starter strength and personal taste all matter. Learning to make kombucha is partly learning to recognise this changing balance.

Do not continue fermenting indefinitely in the belief that longer must be healthier. The drink will become increasingly acidic and may eventually resemble vinegar.

Step 6: Reserve starter for the next batch

Once you are satisfied with the taste:

1. Remove the pellicle with clean hands.

2. Set aside at least 250 ml of unflavoured kombucha.

3. Store the pellicle in that liquid until you make your next batch.

The reserved liquid becomes the starter for your next brew. Do this before adding fruit, herbs or other flavourings.

You may notice that a new layer forms with every batch. You do not need to keep an ever-growing stack of pellicles. One or two healthy layers together with sufficient mature starter liquid are enough.

Once you have harvested the kombucha

Option 1: Refrigerate it as it is

Transfer the kombucha into clean bottles, close them and refrigerate immediately. It may develop a little carbonation, but will usually remain relatively gentle.

Refrigeration slows fermentation; it does not stop it completely. Keep the bottles cold and open them carefully.

This is the easiest and safest option for your first batch.

Option 2: Create more carbonation

For a more sparkling kombucha, add a small amount of fruit, juice or ginger to pressure-resistant fermentation bottles. As a conservative starting point, use approximately:

• 1–2 tablespoons of fruit juice per 500 ml bottle, or

• A few small pieces of fruit, or

• A thin slice of fresh ginger

Leave several centimetres of headspace, close the bottles and keep them at room temperature for one to three days. Then refrigerate them thoroughly before opening.

This second fermentation continues producing carbon dioxide inside a closed bottle. Too much sugar, too much time or an unsuitable bottle can result in violent foaming or, in extreme cases, broken glass. Use bottles designed to withstand pressure, place them somewhere contained and open them slowly over a sink. There is no need to pursue maximum carbonation.

A closed second fermentation can also increase the alcohol content. Home-brewed kombucha should therefore not automatically be treated as completely alcohol-free.

What is normal—and what is not?

Kombucha does not always look attractive while it ferments. Many normal changes are mistaken for contamination.

Usually normal:

• Brown threads hanging beneath the pellicle

• Brown sediment at the bottom

• Bubbles beneath or within the new layer

• A thin, translucent film forming on the surface

• An uneven or lumpy pellicle

• The original pellicle sinking

• A sharp, vinegary smell without putrid or rotten notes

Discard the entire batch if you see:

• Dry, fuzzy growth on the surface

• Circular patches resembling bread mould

• Blue, green, black or distinctly fuzzy white growth

• A rotten or otherwise clearly abnormal smell

Mould grows where oxygen is available, so it usually appears on the surface. If you see mould, do not scrape it away and keep the liquid underneath. Discard the liquid and pellicle, clean the equipment thoroughly and restart with a new culture.

When genuinely uncertain, throw it away. A batch of tea and sugar is replaceable.

Does kombucha improve your health?

Kombucha is one of many fermented foods that bring us into contact with a much wider microbial world. During fermentation, bacteria and yeasts transform the tea and sugar, producing organic acids and other compounds that may interact with the microorganisms already living in our digestive system. These organisms do not necessarily settle permanently in the gut, but even temporary visitors—and the substances they produce—can influence the environment through which they pass.

This matters because the gut microbiome is involved in far more than digestion. It helps maintain the intestinal barrier, communicates with the immune system and contributes to the processing of nutrients and the production of metabolites that can influence inflammation, metabolism and even signalling between the gut and brain. Changes in the microbiome have been associated with many aspects of health, although the relationship is complex: there is no single “ideal” microbiome, and association does not always mean causation.

Fermented foods may be one way of regularly exposing this ecosystem to a greater variety of microorganisms (probiotics) and fermentation products (postbiotics). In one human dietary study, eating a range of fermented foods increased microbiome diversity and was associated with reductions in several markers of inflammation. The foods studied included yoghurt, kefir, kimchi and fermented vegetables rather than kombucha alone, so the finding cannot simply be transferred to every bottle of kombucha. Still, it helps explain why fermented foods may be a useful part of a varied diet: not as a treatment or a shortcut to perfect gut health, but as one way of supporting the living ecosystem with which our health is closely intertwined.

Who should be more cautious?

Because homemade kombucha is unpasteurised, acidic and may contain small amounts of alcohol and caffeine, it is not equally suitable for everyone. Pregnant people, young children, people with significant immune suppression and those advised to avoid alcohol should be particularly cautious and may reasonably choose not to drink home-brewed kombucha.

People with kidney or liver disease, a tendency towards metabolic acidosis, or other significant medical conditions should discuss its use with their clinician. Begin with a small serving—around 100–125 ml—to see how your body responds rather than treating kombucha as something to consume by the litre.

Your next batch will already be easier

The first batch asks you to follow instructions because you do not yet know what you are looking for. By the second or third batch, the changes become familiar: the translucent layer at the surface, the brown yeast threads, the gradual movement from sweetness towards acidity.

That is one of the pleasures of fermentation. You are not pressing a button and receiving an identical product. You are creating the conditions in which a living process can unfold—and learning how to notice when that process is moving in the right direction.

Want to learn more?

My own journey into kombucha brewing began with The Big Book of Kombucha by Hannah Crum and Alex LaGory, a comprehensive but accessible guide to making kombucha at home. It covers everything from your first batch to flavouring, troubleshooting and experimenting with more advanced brewing methods. You can find it in The Health Shift Library.

Continue your Health Shift

I regularly explore practical ways to better understand and support your health—without rigid rules or health advice overload. Subscribe at the bottom of this page to receive new articles and practical shifts in your inbox. Cell, 2021; Nature Reviews Gastroenterology & Hepatology, 2024