Kombucha Common Questions

Making kombucha is a little bit of an experiment. Once you move into the second fermentation, you’re working with a living culture that continues to ferment and produce carbon dioxide.

This is where flavor and carbonation develop—but it’s also where paying attention to your bottles, temperature, ingredients, and fermentation time becomes especially important.

Which Bottles or Jars Should I Use?

The bottles you choose for your second fermentation matter because carbonation creates pressure inside the bottle.

For the second fermentation, choose food-grade bottles specifically designed to hold carbonated beverages. Heavy-duty glass bottles with a secure, pressure-rated closure are a good choice.

EZ-Cap or Flip-Top Glass Bottles

Pressure-rated flip-top bottles are a popular choice for kombucha because they create a tight seal that allows carbonation to build.

Choose bottles designed for carbonated beverages rather than ordinary decorative or storage jars.

Avoid damaged, chipped, cracked, or very thin glass.

Tip: Round bottles are generally preferable to irregularly shaped containers because they distribute internal pressure more evenly.

Glass Bottles With Screw-On Caps

If using a screw-cap bottle, make sure the bottle and closure are specifically designed to withstand pressure from carbonated beverages.

Do not assume that any thick glass bottle or metal cap is suitable for carbonation. Ordinary food jars and bottles aren’t necessarily manufactured to safely contain pressure.

When in doubt, use a bottle specifically intended for carbonated drinks.

How Do I Avoid a Kombucha Explosion?

Bottle explosions happen when pressure builds beyond what the container can safely withstand.

A few things can help reduce the risk:

• Use bottles designed for carbonated beverages.

• Inspect bottles for cracks, chips, or other damage before using them.

• Don’t overfill your bottles.

• Leave appropriate headspace according to the bottle manufacturer’s recommendations.

• Keep fermentation temperatures within a reasonable range.

• Don’t allow bottles to ferment indefinitely.

• Refrigerate the bottles once you’ve reached your desired level of carbonation.

Be especially careful when opening a highly carbonated bottle. Open it slowly and away from your face.

How Long Do I Leave Kombucha Out During the Second Fermentation?

The amount of time needed depends on temperature, the amount of sugar available, the ingredients you’ve added, and how much carbonation you’re looking for.

At approximately 65–72°F, you might begin checking your bottles after 24 hours.

Some batches may need a few days to develop the flavor and carbonation you want.

Rather than relying on a specific number of days, pay attention to the fermentation and refrigerate the bottles once they have reached the carbonation level you’re looking for.

Never shake your sealed kombucha bottles. Pressure can build inside, and shaking can make opening the bottle much more difficult.

What Flavors Should I Use?

This is my favorite part!

Fresh fruit and herbs are wonderful additions to a second fermentation, especially when they’re in season.

Try combinations that sound good to you and experiment with different flavors.

Some ideas include:

• Strawberry & basil

• Blueberry & lavender

• Raspberry & rose

• Ginger & lemon

• Peach & thyme

• Blackberry & mint

• Apple & cinnamon

Start with small batches so you can learn how different fruits and herbs affect both the flavor and carbonation.

How Much Kombucha Should I Put Into the Bottle?

Leave enough headspace in your bottle to accommodate pressure and follow the recommendations for the specific bottle you’re using.

Don’t fill a bottle completely to the top.

The amount of carbonation that develops isn’t determined simply by how little headspace you leave. Carbonation depends on several factors, including available sugars, yeast activity, temperature, fermentation time, and how well the bottle retains carbon dioxide.

Do I Need to Burp My Bottles?

You’ll sometimes hear kombucha makers recommend “burping” bottles by briefly opening them to release pressure.

While this can release some built-up carbon dioxide, repeatedly opening bottles also allows carbonation to escape and makes it harder to know how much pressure is actually inside.

I prefer to reduce the risk at the beginning by using pressure-rated bottles, appropriate headspace, reasonable fermentation times, and refrigeration rather than relying on burping as a safety measure.

If you are concerned that a bottle has become excessively pressurized, handle it carefully and consider moving it to a safe, contained location before opening.

How Do I Stop the Second Fermentation?

Once your kombucha has reached the flavor and carbonation you want, place the bottles in the refrigerator.

The cold temperature slows fermentation and reduces the rate at which carbon dioxide continues to build.

Keep the bottles refrigerated until you’re ready to enjoy them.

Remember that refrigeration slows fermentation—it doesn’t necessarily stop it completely. Some continued fermentation can occur during storage.

A Little Patience Goes a Long Way

The second fermentation is where kombucha becomes especially fun.

You’re taking a fermented tea and giving it another opportunity to develop flavor, aroma, and natural carbonation.

Every batch can behave a little differently. Temperature, ingredients, sugar content, the strength of your culture, and fermentation time all play a role.

So experiment, pay attention, and learn from each batch.

That’s part of the beauty of fermentation.