The complete guide to home kombucha fermentation

Want to start making kombucha for the first time and don’t know where to begin? This guide takes you from empty jar to first bottle. Ingredients, stages, mistakes to avoid: in the order you need them.

Steps for your first batch

1. Prepare the sweet tea

Bring 1 litre of water to a boil. Add 10g of loose leaf tea and steep for 10 minutes. Remove the tea, add 70g of plain white sugar and stir until completely dissolved. Leave to cool to room temperature: the tea must be below 30°C before the next step. The SCOBY won’t survive the heat.

2. Prepare the jar

Use a wide-mouth glass jar. Wash it with hot water and rinse thoroughly: no soap residue, which damages the microorganisms. You don’t need to sterilise it.

3. Add the starter liquid

Pour 110ml of already-fermented kombucha into the jar. This immediately lowers the pH and protects the batch in the first hours.

4. Add the tea and the SCOBY

Pour the cooled tea into the jar. Then place the SCOBY on the surface (it will float, sink, or sit in the middle): all are fine. The jar should be filled to about 5cm from the opening.

5. Cover and leave to ferment

If you have the GetBolla kit, use the lid with the integrated sensor: it sits on top of the jar and, as well as covering it, monitors pH and temperature continuously throughout fermentation. Otherwise, cover the opening with a breathable cloth (muslin, double kitchen paper) secured with a rubber band. Don’t use an airtight lid: the SCOBY needs oxygen. Put the jar somewhere with a stable temperature, between 21 and 29°C, away from direct light.

6. Check and bottle at the right moment

Use GetBolla to know exactly when the moment has come: the sensor tracks pH continuously and sends a notification to your phone when the kombucha is ready to bottle. Alternatively, between day 7 and day 12, start tasting every day. The kombucha is ready when it has a balance between acidity and sweetness, and the pH is between 2.5 and 3.5. When it’s ready, transfer it to bottles with airtight closures and put them in the refrigerator.

The ingredients for a proper kombucha

The quantities below are for 1 litre of water - the base capacity. The GetBolla jar has a 3-litre capacity: scale proportionally based on how much you want to produce.

Each ingredient affects the result in a precise way. They are not interchangeable, but over time you’ll discover which ones you can experiment with.

The first ingredient: tea

Tea provides the nutrients the SCOBY needs (we’ll learn what that word means later), which are nitrogen and minerals. Black tea is the most commonly used because it has the most complete nutritional profile and its flavour is a little stronger and more structured, coming through more clearly in the finished drink. Green tea works, but ferments more delicately and often faster.

Always use loose leaf tea: it releases nutrients more evenly and gives you more control over the result. The GetBolla kit includes selected loose leaf tea, already dosed for the first batch.

What doesn’t work: teas flavoured with essential oils (bergamot, mint, citrus). The oils inhibit the bacteria and can damage the SCOBY. Otherwise, any pure tea variety (for example white tea, oolong tea) is perfect for making kombucha. You can also blend them together, starting fermentation on a mix of different teas. In that case, it’s all about balancing flavours and aromas.

The SCOBY’s fuel: sugar

It’s the fuel of fermentation. Yeasts consume it and transform it. The more sugar you add, the longer the fermentation will be. Plain white sugar is the most predictable. Brown sugar, honey, and other sweeteners work but introduce variables that make results hard to replicate.

The real star: the SCOBY

This is a symbiotic culture of bacteria and yeasts. The more active and healthy it is, the faster and more regular the fermentation. An old or poorly stored SCOBY ferments irregularly.

A healthy SCOBY is rubbery, beige-brown in colour, with no green or black spots. Brown strands in the liquid are normal: those are the yeasts.

The starter liquid: what gives fermentation its kick

This is already-fermented kombucha that you add at the start of the batch. It immediately lowers the pH of the fresh liquid, creating an acidic environment that protects the fermentation from contamination.

Without starter liquid, or with too little, the batch is vulnerable in the first 24–48 hours.

Important: add the starter liquid and SCOBY only once the tea has cooled below 30°C. Heat kills the microorganisms.

How the jar changes day by day

Fermentation is not linear: it has distinct stages, each with different characteristics.

The factors that affect fermentation — and how to keep them under control

Temperature, type of tea, SCOBY condition, amount of sugar: these four factors determine the speed of fermentation and change from batch to batch. The old answer to “how long does it take?” was always “it depends.” With GetBolla, it no longer is: the sensor monitors pH and temperature continuously and tells you exactly where you are in the process, regardless of how these factors are playing out.

1. Temperature

It’s the most important factor. Microorganisms work faster when it’s warm and slower when it’s cold. The ideal range is 21 – 29°C.

• Below 18°C: very slow fermentation, can take 3+ weeks
• 18 – 21°C: normal fermentation, 10 – 14 days
• 21 – 29°C: ideal range, 7 – 12 days
• Above 29°C: very fast fermentation, risk of over-fermentation in 5 – 6 days

Your kitchen temperature changes between summer and winter, between day and night. A July batch doesn’t behave like a January batch, even with the same ingredients. Use GetBolla to monitor temperature continuously: the sensor alerts you if it goes outside the ideal range, without you having to check every day.

2. The SCOBY

A young, active SCOBY ferments faster than an old one or one just reactivated from the refrigerator. Thickness also matters: more active surface area means faster fermentation.

If you’re using a new SCOBY, the first 1 – 2 batches may be slower than normal. That’s normal: it’s adapting to your environment.

3. The type of tea

Black tea ferments more robustly and predictably. Green tea tends to ferment faster but with a more delicate aromatic profile. White and oolong teas are more variable.

The tea you use doesn’t just change the taste: it changes the speed and behaviour of fermentation.

4. The amount of sugar

More sugar means more fuel for the yeasts, so a longer fermentation before the pH drops to the ideal range. The standard amount is 60 – 80g per litre. Above 100g, fermentation becomes unpredictable.

How to know when it’s ready

There are three ways. They work best together.

Use GetBolla — the most precise, hands-off way

The GetBolla sensor monitors pH continuously from inside the jar and sends a notification to your phone when the kombucha is ready to bottle. You don’t need to remember to check, you don’t need to measure by hand, and you don’t have to rely on taste alone. It’s the most reliable way to never lose a batch.

pH - the objective indicator

pH measures acidity on a scale from 0 to 14. Ready kombucha has a pH between 2.5 and 3.5.

Below 2.5 it’s over-fermented. Above 3.5 it’s still too sweet.

If you’re not using GetBolla, you can measure with test strips (cheap but imprecise) or a digital pH meter (more precise, requires calibration).

Taste

Taste every day starting from day 5 – 6. Ready kombucha has a balance between acidity and sweetness: it should be neither too sweet nor too sour.

The problem with taste is that it’s subjective. Two people can taste the same batch and give different assessments.

Appearance

A healthy SCOBY in active fermentation produces visible bubbles on the bottom and sides of the jar. A new layer of SCOBY forms on the surface: that’s normal.

Appearance alone is not enough. Use it as confirmation, not as a primary indicator.

What kombucha fermentation is

Kombucha is fermented tea. You add a SCOBY to sweetened tea, wait, and the microorganisms transform the sugar into organic acids, CO₂, and a small amount of alcohol.

The result is a slightly acidic, fizzy drink with an aromatic profile that depends on dozens of variables.

SCOBY is an acronym: Symbiotic Culture Of Bacteria and Yeast. It’s not an ingredient you add: it’s a living ecosystem that works for you.

Its work has two phases:

1. Yeasts consume the sugar and produce alcohol and CO₂
2. Acetic bacteria convert the alcohol into organic acids, primarily acetic acid and gluconic acid

These acids lower the pH of the liquid. When the pH drops enough, the kombucha is ready.

What goes wrong (and how to avoid it)

Bottling too early

The batch seems ready but the pH is still above 3.5. Result: sweet, flat, under-fermented kombucha. The second fermentation doesn’t produce enough CO₂ because there’s too little acid.

Forgetting the jar

You come back after a week and the pH has dropped below 2.5. The kombucha tastes like vinegar. It’s not dangerous (you can use it as starter liquid or as a condiment), but as a drink the batch is lost. With GetBolla, this doesn’t happen: the sensor sends you a notification as soon as the pH enters the alert zone, so you can act in time.

Irregular temperature

The jar near a window in summer: temperature swings between 18°C at night and 30°C during the day. Fermentation becomes unpredictable. Find a spot with stable temperature.

Too little starter liquid

Less than 10% leaves the batch vulnerable in the first hours. Use at least 100ml per litre of tea.

Changing too many variables at once

You changed the tea, the amount of sugar, and the temperature in the same batch. The result is different, but you don’t know why. Change one variable at a time if you want to learn from the process.

Second fermentation: fizzy and flavoured

The first fermentation happens in an open jar and transforms sweet tea into kombucha. The second fermentation happens in a sealed bottle, after transfer, and has two purposes: building carbonation and adding flavour.

Transferring to bottles

When the kombucha is ready (pH 2.5 – 3.5, balanced taste — or when GetBolla notifies you), before bottling, gently stir the liquid in the jar to distribute the yeasts evenly, as they tend to settle at the bottom. Then transfer it into bottles with airtight closures: glass bottles with a swing-top or a sturdy screw cap. Leave about 3 – 5 cm of headspace from the mouth: the CO₂ that forms needs room.

Before filling the bottles, set aside your starter liquid for the next batch: take 110 ml of kombucha from the bottom of the jar, where the yeasts are most concentrated, and keep it at room temperature.

Adding flavours

The second fermentation is the right moment to flavour your kombucha. During the first fermentation you don’t add anything: new ingredients would interfere with the SCOBY and make results hard to replicate.

What you can add to the bottles before sealing:

• Fresh or frozen fruit: ginger, mango, strawberries, raspberries, peach
• Fruit juices: lemon, pomegranate, apple, orange
• Spices: cinnamon, cardamom, black pepper
• Flowers and herbs: lavender, hibiscus, mint, basil

The amount depends on the intensity you want: start with 1 – 2 tablespoons of fresh fruit or 1 teaspoon of juice per 250 ml of kombucha. Increase in subsequent batches if you want more flavour.

Second fermentation timing

Leave the sealed bottles at room temperature for 2 – 4 days. During this time the remaining yeasts consume the residual sugars (and those added with the fruit) and produce CO₂ which, unable to escape, dissolves into the liquid.

Speed depends on temperature and the amount of sugar:

• At 21 – 24°C: 2 – 3 days are usually enough
• With a lot of fruit or juice: carbonation builds faster
• With little fruit or very acidic kombucha: may take 3 – 4 days

Managing bottle pressure

Open one bottle each day to check the pressure: open slowly, let a little gas escape, then reseal immediately. This is called “burping”. If by the second day the pressure is already high, move all the bottles to the refrigerator: cold almost completely stops fermentation and preserves the carbonation.

In the refrigerator, kombucha keeps for 2 – 4 weeks. The longer it sits, the more the acidity slowly increases.

FAQ

Is home-made kombucha safe?

Yes, if the pH drops below 4.0 within the first 24 – 48 hours. The acidic environment protects against contamination. If you see green or black mould on the surface (not on the SCOBY), throw everything out and start again.

Can I use any container?

Glass is the best material. Avoid metal (it reacts with acids) and porous plastic. The jar must have an opening wide enough to let the SCOBY breathe: cover with a breathable cloth or the GetBolla lid, not an airtight lid.

How much starter liquid should I use?

At least 10% of the total volume. For a 1L jar, use 100ml of already-fermented kombucha.

Can I make kombucha without a SCOBY?

Technically yes, starting from a bottle of unpasteurised kombucha from the supermarket. But it’s slower and less reliable. An active SCOBY is the best starting point. If you don’t have a SCOBY yet, the complete GetBolla kit includes a 3-litre jar, loose leaf tea, starter liquid, and active SCOBY: everything you need for the first batch.

What do I do with the SCOBY between batches?

Keep it in a SCOBY hotel, a jar with already-fermented kombucha, at room temperature or in the refrigerator. In the refrigerator it keeps for months, but it needs a few days to reactivate before the next batch.

My batch isn’t fermenting: what do I do?

Check the temperature (must be above 18°C), the amount of starter liquid (at least 10%), and the condition of the SCOBY. If the pH doesn’t drop after 48 hours, the SCOBY may not be active. With the GetBolla sensor you can keep an eye on the pH from day one, so you know immediately if something is wrong.

I’m leaving for a week - where do I store the SCOBY?

It depends on how warm your place gets. If the temperature goes above 26–28°C, put the SCOBY in the fridge: submerged in already-fermented kombucha in a sealed jar, it keeps perfectly for weeks. The cold almost completely stops microbial activity, so there’s no risk of over-fermentation. When you’re back, take it out 24–48 hours before you need it: it needs time to come back to room temperature and reactivate. If your home stays cool (below 22°C), you can leave it out in a SCOBY hotel, but check the pH when you return: it may have fermented more than expected.

Want to understand pH in depth first? Read: kombucha pH →