Who loves bubbles in their beverage? We do! In fact, when most people get into bottling Kombucha at home, they desire more fizz. Any why not? It’s fun, adds texture and flavor, looks cool in the glass and reminds many people of good times. How exciting when a new Booch is opened, bubbles rush madly upward, increasing exponentially, frothing to the top of the bottle and spilling forth gently!
There may even be a secret reason we crave those carbonated quaffs…could it be nutrition? Natural fizz, the kind found when bottling Kombucha, JUN and Kefir home brews, indicates the presence of living yeast, which contain B-vitamins that the body can use in bioavailable form.
Whatever the reason, no one loves scraping glass and fermented fruit off the ceiling, walls, and dog at 2am.
If you’re bottling Kombucha, Jun, water kefir or milk kefir, you’re working with a living drink. Yeast + sugar + warmth + a sealed bottle = carbonation. Get that balance right and you have gorgeous, lively fizz. Get it wrong and you can end up with geysers, overflow…or in rare cases, dangerous bottle bombs.
This guide walks you through:
Deep breath. You can absolutely have great fizz and a safe kitchen. Let’s go.
All naturally carbonated drinks work on the same equation:
Yeast + Sugar + Time + Warmth + Closed Bottle = CO₂ (bubbles & pressure)
Inside a sealed bottle, those bubbles have nowhere to go. If pressure builds faster than it can be absorbed into the liquid or held by the glass, it will find a weak point:
Good news: all of these are 100% preventable once you know what to look for.
Kombucha Mamma Says
You might be thinking, “What about plastic bottles? Problem solved!”
We say “PASS!”
While some people reuse soda or water bottles, they are made of material not designed for the acidity of any of our favorite fermented drinks. Even in one use they can absorb a plastic flavor.
We’ve never felt comfortable with the risk or the taste when bottling Kombucha. But if it makes any homebrewer feel more at ease, then by all means use them.
Before we zoom into the details, here are the non-negotiables:
Once these are in place, your risk of explosions plummets.
Over-fermented base + extra sugar in the bottle = rocket fuel.
Best choices:
Pass or use with caution:
Sugar is yeast’s party fuel.
Safer alternative: flavor in the brewing vessel for 1–3 days after removing the culture & starter, then strain and bottle the flavored liquid. Much less mess, same great taste.
Yeast is good. Too much yeast + too much sugar = trouble.
Aim for balanced: some “ooglies” = character. A solid plug of sludge = overkill.
Overfilling can cause:
Second ferment (F2) is where carbonation really happens.
Pick:
Avoid:
In warm months, check once a day:
If they’re very active:
For very aggressive batches, you can carefully “burp” (see below), but we prefer to get ahead of it via time + temperature + bottle type rather than constant burping.
Or adding purees at serving instead of into the bottle
Bonus: use saved yeast for sourdough starter or experiments.
It’s tempting to leave bottles on the counter “just one more day” for more fizz…then another…and another.
If you want more fizz after that, age them cold instead of pushing them at room temp.
If your house is 80–90°F (27–32°C) inside:
Cooler second-ferment temps = slower pressure build + more control.
Think like champagne, not cheap beer.
Best:
Why rounded?
Pressure distributes more evenly in curved glass than in corners. Square bottles are more prone to stress points.
You can’t control every variable — this is a living beverage, after all.
If something does go bang, you’ve limited the damage to one contained area, not the entire kitchen.
Kombucha is usually your medium-speed, medium-pressure bottling buddy.
Treat Jun like Kombucha’s more excitable cousin:
Respect water kefir. For real.
If any drink will surprise you with sudden “champagne showers,” it’s often water kefir.
Milk kefir has its own quirks (separation, pressure in the whey), but it tends to be the least explosive of the four—still worth treating with respect.
It happens. Here’s how to handle it safely:
If you really don’t feel safe:
If one bottle has exploded or is clearly over-pressurized, treat the whole batch with caution — they’ve all experienced similar conditions.
Aim for about 5–10% of the bottle volume. Less for purees and juices, which ferment faster.
Not always. We prefer to manage carbonation through time, temperature, bottle choice, and sugar control first. Burping is a last resort for very active batches.
Not necessarily, but it was over-carbonated. Next time, use less sugar in F2, shorten the warm-time, or store cooler.
We don’t recommend standard thin beer bottles. They were not designed for naturally carbonated ferments with variable pressure and are more prone to breaking.
They’re less likely to shatter, but not ideal for long-term use with acidic drinks like Kombucha, Jun, and kefir. If you use them occasionally, avoid heat and don’t reuse endlessly.
Bottling your Kombucha, Jun, water kefir, and milk kefir should feel fun, not scary.
Once you understand:
…you can confidently create beautifully bubbly drinks without turning your kitchen into a fermentation war zone.
You’re not just bottling a beverage.
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