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There is a misconception around the idea of carbonation. I get countless emails asking if something is wrong with their kombucha, it isn’t fizzy at all and it has been fermenting for one, sometimes two weeks. The answer lies in a very important detail–during the primary fermentation, you are conducting an open-air ferment, meaning that all of the carbonation that is produced is allowed to evaporate out immediately. Think of what happens when you leave the cap off of a soda bottle–you come back to a flat, off-tasting product.

What makes kombucha fizzy?

During fermentation, yeast consume sugar and convert it into two byproducts–alcohol and CO2. CO2 is a gas that wants to escape and will if allowed. Even if you have a big fat SCOBY capping the top, the gas molecules are tiny and will find a way out. If you cap off the vessel, making it air-tight, it forces the molecules to dissolve into the liquid and provides the phenomenon which we refer to as carbonation, or fizziness!

How do you make fizzy kombucha?

This is often referred to as a secondary fermentation, because it is just that. You take a fermented product (your kombucha) add a little bit of sugar and let it ferment again. This time, rather than the CO2 escaping, you place an air-tight lid on and force the carbonation to dissolve into the kombucha.

Do you have to add more sugar?

The sugar is a key component in the secondary fermentation because it facilitates the carbon dioxide production. Without sugar, there is no CO2 production and since most of the sugar that you put in initially has already been eaten, it helps to add a little during bottling. It’s what is referred to as “bottle conditioning” in the beer world. More than likely, there will be some residual sugars leftover from your primary fermentation so if you really don’t want to add any extra, you can certainly give it a try.

What kind of sugar should you add?

This is entirely up to you! I like to take this opportunity to add fresh fruit. The fruit doubles as both a source of sugar and delicious flavor! Results will vary a bit depending on the type of fruit you use, but that’s the fun in experimenting! If you’d prefer, you can just add a little bit more cane sugar or use honey, agave, maple syrup, etc! As long as the sugar is real sugar and not a “sweetener” it will work for the secondary fermentation. See this post for more information about sugar and kombucha.

What container should you use for a secondary fermentation?

There’s two things to consider when choosing bottles or vessels for your secondary fermentation. First, is it airtight? If air can escape, so can the carbon dioxide gas. Second, will it fit in your refrigerator easily?

Grolsch-style flip top bottles are great airtight options. You can choose either 16oz or 32oz versions of them, but for me, the 32oz bottles are too tall to fit into my refrigerator. The 16oz bottles are a great, their only downside is that they can be a little tough to clean because the opening is small. If you have a bottle brush it makes the cleaning process super easy.

Another great option is to use mason jars, which allows you to make 32oz batches without worrying about the height of the flip top bottles. In order to make mason jars airtight, you need to get air-tight lids that have a gasket fitted inside, like these ones. The gasket is the key to creating that seal. The metal lids that come with the jars not only aren’t fully airtight but rust super easily.

Why not do the secondary in the container that you brewed in?

You want to keep your main brewing vessel for just that–brewing. Keeping your first and second fermentation separate creates a stable environment for your SCOBY to live. Adding foreign things like fruit or spices may affect the health and balance of your culture in the long run so you want to keep your SCOBY happy and healthy living on tea and sugar.

Not getting carbonation, even after a secondary fermentation?

Don’t worry too much, carbonation can be finicky. Often temperature has much to do with it, but sometimes the yeast just don’t want to perform for you. Just keep on brewing and it should come with time.

There are a few things you can do to try and boost your yeast population:

1. Use teas that have a high tannin content that help nourish yeast, such as our Elements Water Tea Blend.
2. Try and maintain a temperature of 78-80F to give the yeast a hand up over the bacteria.
3. Manually aerate your brew during the primary fermentation. Kombucha is an aerobic fermentation, meaning it requires oxygen. Sometimes the oxygen that it gets at the surface isn’t quite enough. You can manually provide oxygen by stirring your kombucha vigorously every few days. This often gives it the jump start it needs!

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