You open your bottle of homemade kombucha, expecting the typical ‘spritz’ of fizzy drinks… and nothing. No foam, no bubbles, almost no life in the glass. The taste is good, but the texture disappoints you. You dreamt of a lively, fizzy kombucha, but what you get is an almost flat drink.

It’s one of the most common frustrations of novice brewers. Fortunately, the good news is simple: truly sparkling kombucha is not a matter of luck, but of method. A lively, healthy culture (like a well-balanced SCOBY of kombucha, supplied with its starter liquid), a little sugar at the right time, the right bottles and good temperature management are all it takes to turn a timid kombucha into a naturally fizzy drink.

In this comprehensive guide, we take a look at :

• where exactly does the gas in kombucha come from?
• why your kombucha sometimes stays flat despite your best efforts
• how to organise an effective second fermentation to boost sparkling wine
• which flavourings (fruit, juice, sugar, ginger…) to use for more generous bubbles
• how to avoid the reverse. The kombucha bomb exploding in the kitchen
• how to adapt all this to your own pace and taste

The aim is not to make a standardised drink, but to teach you how to ‘pilot’ your bubbles to obtain the level of fizz you like, while maintaining a pleasant, safe and controlled kombucha.

Understanding where kombucha’s fizz comes from

To get more bubbles, you first need to understand how they form.

CO₂, a natural by-product of fermentation

In your kombucha, it is mainly the yeasts that :

• consume sugar
• produce alcohol and carbon dioxide (CO₂)

Bacteria then convert some of the alcohol into organic acids, but it is the yeast that is responsible for the gas.

As long as the CO₂ can freely escape to the outside, your kombucha :

• « works »
• acidifies
• but still lacks sparkle

For the drink to become carbonated, this CO₂ must be trapped in a closed space.

First fermentation, an escaping gas

During the first fermentation :

• your kombucha is in a large jar
• the opening is covered with a cloth or gauze
• the air circulates freely

Yeast does produce CO₂, but :

• the gas escapes through the fabric
• it does not accumulate in the liquid
• the kombucha becomes acidic, but not really fizzy

The first fermentation is therefore mainly used :

• to transform sweet tea into kombucha
• to install the right acidity
• to lay a healthy foundation for the future

Don’t look for a big ‘pschitt’ at this stage. That’s not its role.

Second fermentation, where the bubbles are really created

The real sparkle develops during the second fermentation, when you :

• put your kombucha in hermetically sealed bottles
• add a small source of sugar (sugar, honey, fruit, juice…)
• let the yeasts consume the sugar in this new closed space

The CO₂ product:

• can no longer escape
• accumulates in the bottle
• dissolves in part in the liquid
• creates pressure and bubbles

The art of sparkling kombucha lies in managing this second stage:

• amount of sugar
• type of flavour
• secondary fermentation time
• temperature
• choice of bottles

That’s what we’re going to talk about next.

Why isn’t my kombucha fizzy enough?

Before making corrections, it’s useful to understand what’s going wrong. The main reasons for low-gas kombucha are almost always the same.

Not enough secondary fermentation

It’s a very common mistake to bottle kombucha, chill it straight away and then be surprised when there aren’t many bubbles.

The cold:

• significantly slows down yeast activity
• limits the production of CO₂

If you put your bottles in the fridge too early, the carbonation process has almost no time to take place.

Not enough sugar to feed the yeast in the bottle

If you bottle :

• a very dry kombucha (very little residual sugar)
• without adding sugar or fruit

…the yeasts have almost nothing left to consume in the second fermentation. They therefore produce very little CO₂.

Conversely, if you add a little sugar (or fruit, or juice) :

• you give the yeast something to get going again
• they produce more gas
• you get more fizz

Bottles that close poorly or are unsuitable

If your bottles :

• don’t really close hermetically
• allow some of the gas to escape
• have tired or ill-fitting plugs

… the CO₂ goes away, the pressure doesn’t rise, and the bubbles remain timid.

Swing-top bottles (like craft beer bottles with mechanical closures) are very popular precisely because they :

• close well
• withstand pressure
• are easy to open and close

We’ll come back to this later.

Sluggish cultivation or difficult conditions

Finally, it is possible that :

• your SCOBY is a little tired
• your yeasts are less active (culture kept for a very long time without food, prolonged refrigeration, etc.)
• the temperature is too low (below 20°C, everything slows down)

In this case, fermentation in the bottle will be slow and the gas will take much longer to develop.

The essentials for sparkling kombucha

Before adding advanced tips, make sure the basics are in place.

A healthy and active culture

A SCOBY of live kombucha, accompanied by an acidic starter liquid, is the foundation. A good strain :

• ferments regularly
• produces a stable kombucha
• contains sufficiently active yeasts to restart in the bottle

If your crop is very old, poorly nourished, or from a dubious source, you risk :

• irregular fermentation
• less bubbly
• more difficulty adjusting taste and gas

Starting with a healthy, well-balanced SCOBY makes things much simpler.

A well-fermented basic kombucha

Before thinking about bubbles, you need a solid foundation:

• a properly brewed sweet tea
• sufficient initial fermentation time to ensure a balanced taste (no pure sweet tea or undrinkable vinegar)
• an appropriate sugar/tea/liquid ratio

If your basic kombucha is :

• still very sweet
• or, on the contrary, already almost vinegary

… the behaviour of the second fermentation will be different. Ideally, for a pleasant fizz, the base kombucha should be semi-sweet/half-acidic, leaving a little leeway for the rest of the process.

Bottles adapted to fermentation

For a good secondary fermentation, choose :

• thick glass (bottles of beer, lemonade, artisanal kombucha)
• with mechanical stopper or cap that really closes
• without cracks or weaknesses

What to avoid:

• screw-top jars with loose lids
• old, fragile bottles
• very thin glass bottles

Some brewers use a plastic bottle (such as a water bottle) as a « test » bottle:

• they fill it like everyone else
• they squeeze it every day to feel the pressure build up
• when the bottle is very hard, they know that the gas is present and can put everything in a cool place

It’s a simple trick to assess the level of fizz without opening every bottle.

The step-by-step method for truly sparkling kombucha

Let’s move on to practice. Here’s a simple method that you can adapt.

Step 1, prepare a batch of basic kombucha

Prepare your kombucha as usual:

• properly brewed tea (black, green or blended)
• sugar (generally 60 to 80 g per litre for the starter tea)
• complete cooling of the tea
• adding SCOBY and starter fluid
• first fermentation in a cloth-covered jar

Leave to ferment:

• until you get a taste you like. No sweet tea, no extreme vinegar
• generally between 6 and 10 days depending on temperature, season and crop strength

Taste every day from day 5 or 6 to find your « ideal window ».

Stage 2, preparing the bottles

Clean your bottles:

• rinse thoroughly in hot water with a little washing-up liquid
• rinse thoroughly to remove all traces of product
• leave to drain in the open air

Make sure that :

• mechanical plug seals are in good condition
• nothing leaks when you close the empty bottle and give it a gentle shake

Simple but rigorous hygiene avoids unpleasant surprises (odours, contamination).

Step 3, add the « food » for the second fermentation

For your yeasts to produce gas in the bottle, they need a little sugar. You have several options:

Simple sugar :

• 5 to 10 g sugar per litre of bottled kombucha (adjust to taste)
• you can dissolve it in a little basic kombucha and then pour it into the bottles

Fresh or frozen fruit :

• a few pieces of strawberry, mango, peach, pineapple, pear…
• or a small handful of red fruit
• the quantity depends on the strength of your yeast and your taste preferences

Fruit juices :

• 5 to 10% juice (apple, grape, red fruit) in the bottle
• be careful, it’s highly fermentable. The gas can rise quickly

Honey, syrup, wholegrain sugar :

• also possible, in small quantities
• beware of strong aromas (strong honey, highly flavoured sugar) which can overpower the taste

Start small, especially at the beginning. It’s better to have kombucha that’s not fizzy enough than bottles that explode.

Step 4, filling the bottles

Pour your filtered (or unfiltered, as you prefer) kombucha into the bottles:

• fill to about 2-3 cm below the neck
• leave a small space for the gas, but not too much (too much air = less pressure in the liquid)
• If you have added sugar directly into the bottle, close it quickly after filling.

You can filter out the deposits and filaments if their appearance bothers you, but this is not obligatory for sparkling wine.

Step 5, Allow the second fermentation to take place at room temperature

Place the bottles :

• at room temperature (ideally 22-26°C)
• out of direct sunlight
• in a dish or tray to contain any spillage

Leave to ferment:

• generally 2 to 5 days depending on the temperature, the amount of sugar and the vitality of your crop
• checking the pressure every day (with a test plastic bottle, or by opening a bottle very slightly to feel the « pschitt »)

The hotter the weather, the faster it goes. At the height of summer, 24 to 48 hours can be enough for a very pronounced fizz.

Step 6, chill to slow fermentation

When the gas level is right for you :

• place the bottles in the refrigerator
• cold greatly slows down yeast activity
• the pressure stabilises (or increases very slowly)

Chilled kombucha:

• sometimes continues to gain in complexity
• keeps its fizz for several days or even weeks

You can then :

• open gently to avoid geysers
• serve well chilled, pouring gently to keep the bubbles

Boosting fizz, advanced adjustments

Once you’ve mastered the basics, you can play around with a number of parameters to increase the fizz even further, while remaining cautious.

Use highly fermentable ingredients

Certain ingredients are particularly good at nourishing yeast:

• apple juice
• grape juice
• mango or pineapple purée
• ginger syrup (ginger + sugar)

In small quantities, they give :

• lots of aromas
• a great deal of excitement

But they also demand :

• closer monitoring
• shorter second fermentation times
• sometimes regular degassing (opening the bottles slightly to release a little pressure)

Do not underfill cylinders

The more air your bottles contain, the less pressure is concentrated in the liquid. For a good compromise:

• fill to 2-3 cm below the cap
• avoid leaving a large empty space

Correct filling:

• helps dissolve the CO₂ in the kombucha
• gives a cleaner, denser fizz

Keeping some active yeast in the liquid

If you filter your basic kombucha very finely, you remove most of the yeast. Result:

• fewer micro-organisms in bottles
• less production of CO₂
• weaker fizz

For a good balance, you can :

• filter coarsely (colander, sieve) to remove large filaments
• allow some of the suspended yeast to pass through

That’s more than enough for a dynamic second fermentation.

Safety, avoid exploding bottles

More fizz is nice… but too much pressure can be dangerous. A few simple rules will help you enjoy your bubbles in complete safety.

Use cylinders suitable for the pressure

Give priority to :

• thick glass beer bottles
• lemonade bottles with mechanical stoppers
• bottles designed for pressurised drinks

Absolutely avoid :

• old, fragile jars
• thin or decorative cylinders not designed for gas
• cracked or chipped containers

If in doubt, use a plastic bottle as a test to assess the strength of the fermentation.

Regularly monitor bottles undergoing secondary fermentation

Don’t leave your bottles :

• at room temperature for 10 days without touching them
• especially if you have added a lot of sugar or juice

Instead:

• check every day
• open a bottle slightly to feel the pressure if necessary
• as soon as you feel the fizz is sufficient, chill it in the fridge

In summer, a second fermentation can be very rapid. Better to watch too much than too little.

Degas if necessary

If you feel that :

• the pressure is very strong
• opening the bottle seems dangerous
• the test plastic bottle is as hard as a rock

You can :

• Very gently open the stopper above the sink, holding it firmly.
• allow the gas to escape gradually
• reseal and leave for another day or two in a cool place to stabilise

If in any doubt, don’t hesitate to throw away a bottle rather than risk an accident. Safety comes before a few centilitres of drink

Adapt the fizz to your taste

The advantage of making your own kombucha is that you can choose the level of fizz:

• some people like kombucha with just a hint of bubbles
• others prefer an effervescence akin to a traditional soda

You can play on :

• the quantity of sugar/fruit added during secondary fermentation
• duration at room temperature (1 to 5 days)
• the temperature of the room (the warmer it is, the faster it goes)
• the moment you chill

With a simple notebook (date, ingredients, temperature, duration), you will quickly see patterns appear:

• « with 1 teaspoon of sugar per bottle, 2 days at 24 °C are enough ».
• « with grape juice, only 24 hours otherwise it’s too strong ».
• « in winter, it takes 4 days in my kitchen at 20°C ».

Little by little, you will no longer be subjected to your bubbles; you will control them.

Frequently asked questions, sparkling wine and kombucha

My kombucha still doesn’t fizz after 3 days, why?

There are several possibilities:

• the room is too cold (below 20°C). The second fermentation takes longer
• you haven’t added sugar or fruit. Little food for yeast
• your culture is very tired. Few active yeasts
• the cylinders don’t close properly. The gas escapes

Possible solutions:

• leave for a further 1 to 2 days at room temperature
• add a little more sugar or juice next time
• check the condition of your cylinders and seals
• if the problem recurs frequently, consider starting with a stronger SCOBY

My kombucha is very fizzy but lacks flavour. What can I do?

This is often a sign that :

• you used a lot of simple sugar in secondary fermentation
• but few aromas (fruit, herbs, spices)

You can :

• reduce pure sugar
• slightly increase the proportion of aromatic ingredients (ginger, citrus zest, red fruit)
• ensure that the kombucha base already has a good flavour profile (quality tea, well-executed fermentation)

My kombucha geysers when I open it. How can I avoid this?

Your second fermentation is undoubtedly very advanced:

• lots of added sugar
• long life at room temperature
• high temperature

To limit geysers:

• chill earlier
• open the bottles very gently, very cold
• in the event of high pressure, degas a little the day before tasting

You can also use larger bottles or fill slightly less to leave a little more margin.

Is it possible to obtain sparkling kombucha without secondary fermentation?

Very little.

The first fermentation, in a cloth-covered jar, allows the gas to escape. To get real bubbles, you need :

• a closed container
• a little sugar
• of active yeast

This is precisely what the second fermentation in the bottle does. It’s virtually indispensable if you want a truly sparkling kombucha.

Is it always necessary to add flavour for sparkle?

No.

You can obtain a very fizzy kombucha:

• by simply adding a small amount of sugar (white sugar, cane sugar, honey…)
• no additional fruit or flavourings

Fruit and juices are simply a way of :

• feed the yeast
• add flavour
• personalise your drink

Conclusion, sparkling kombucha is more a question of method than luck

There’s nothing mysterious about making kombucha more sparkling. It’s a question of balance between :

• a healthy and vibrant kombucha culture
• a well-fermented basic kombucha
• bottles that close properly
• a little sugar at the right moment
• a few days of secondary fermentation at the right temperature
• chilling in a cool place to stabilise

By understanding where the bubbles come from and what the yeast needs, you can transform a slightly shy drink into a lively, joyful kombucha, with the level of effervescence that suits you.

With a quality strain, a SCOBY of living kombucha accompanied by its acidified starter liquid and clear instructions, you start with a precious advantage. Yeasts and bacteria ready to work for you, batch after batch. Then it’s up to you to play with the sugar, the time and the temperature to find your signature. That little « spritz » when you open the glass, the fine foam in the glass, the dancing bubbles… and the pleasure of saying. « This sparkling kombucha, it was I who made it ».