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.
1. Understanding where kombucha’s fizz comes from
To get more bubbles, you first need to understand how they form.
1.1. 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.
1.2. 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.
1.3. 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.
2. 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.
2.1. 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.
2.2. 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
2.3. 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.
2.4. 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.
3. The essentials for sparkling kombucha
Before adding advanced tips, make sure the basics are in place.
3.1. 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.
3.2. 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.
3.3. 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.
4. The step-by-step method for truly sparkling kombucha
Let’s move on to practice. Here’s a simple method that you can adapt.
4.1. 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”.
4.2. 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).
4.3. 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.
4.4. 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.
4.5. 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.
4.6. 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
5. 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.
5.1. 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)
5.2. 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
5.3 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.
6. 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.
6.1. 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.
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.
6.3. 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
7. 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.
8. Frequently asked questions: sparkling wine and kombucha
8.1. 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
8.2. 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)
8.3. 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.
8.4. 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.
8.5. 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”.
