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Fermentation Time

Hello Kombucha Friends…

I’ve been receiving many questions asking, “How long should I ferment my brew?”

This is an excellent question and the answer depends on you. First, let’s look at the factors that influence fermentation time for Kombucha.

  1. Temperature
  2. Taste
  3. Size & Shape of Vessel
  4. Acids expression

1. Temperature

The hotter the temperature, the faster the ferment. Conversely, the cooler the temperature, the slower the ferment. The ideal temperature for fermenting Kombucha is 70-80 degrees F. In the summer, my brew time is anywhere from 10-12 days, whereas in the winter it can be 2 weeks or longer. Sometimes I use a heating pad in the winter, but since it doesn’t get below freezing in Southern California, it’s not really necessary.

2. Taste

This is the deciding factor for most people. I recommend that after 7 days of fermenting, you take a straw and insert it under your SCOBY and take a sip. Is it too sweet? Too tart? Not tart enough? You are the ultimate decider in this process. What tastes delicious to you? And your taste will evolve over time the longer you brew Kombucha. I’ve also discovered that I am better able to sense when the Kombucha is ready based on how the weather has been, the date it was brewed, etc.

How to fix the flavor


There are a couple of things you can do to improve the taste of your Kombucha if it has been brewed too long.

*Add some less mature Kombucha to the more mature Kombucha to even out the flavor
*Dilute with water or juice
*Use it as vinegar (you can use really tart Kombucha the same way you use vinegar)

Once you found the flavor you like, stick it in the fridge. The drop in temperature will slow down the fermentation process.


Allow your Kombucha to continue to ferment. If after a couple of weeks your Kombucha is still too sweet, then your culture may have fallen dormant and you will need to revive it.

2ndary Fermentation

If you enjoy the 2ndary fermentation process, then you might not want your brew to be as tart since it will be fermenting a little longer – however, the addition of sugar (from the fruit or ginger,etc) will also add a little sweetness.

I keep a log book to record the date I brewed my batch, since I have multiple batches going at once, this keeps it easy to know which one will come to fruition next.

3. Size and Shape of Vessel

There is a bit of physics that goes into brewing Kombucha. Your culture will always grow to the size of the vessel – meaning that whatever size your SCOBY is, the new culture will always grow so that it completely seals off the aperture of the vessel.

I ferment in gallon sized pickle jars – they are more tall and less wide. Therefore the surface area covered by the SCOBY is less than the depth of my vessel. It will ferment more slowly since less surface area to depth is covered.


I also ferment in a gallon sized glass bowl with a really wide mouth. Therefore the surface area covered by the SCOBY is more than the depth of my vessel. It will ferment faster because there is more surface area to depth covered.

Short depth and more surface area in a Kombucha brewing vessel can decrease the fermentation time as demonstrated in this photo

4. Acids Expression

Based on previous research, it has been discovered that there are certain amino acids that aren’t expressed in the fermentation process until at least 30 days have passed. For most of us brewing a gallon batch, at 30 days, our brew would be undrinkable and taste like vinegar. This is why many people prefer to do a continuous brew – Check out the page about it here.

On the GT’s bottles you will see that his has been fermented for 30 days, and yet it is quite delicious. My theory has been that he brews it in vessels of such a size and volume that even after 30 days, the ferment is still potable. This is only a theory as he doesn’t allow visitors into his facility.

In the end, it really is up to you in terms of how long to ferment your Kombucha. The more times you engage in the process, the more intuitive this will become.

Happy Brewing!

Hannah Crum, the Kombucha Mamma!Hannah Crum is The Kombucha Mamma, founder of Kombucha Kamp, Industry Journalist & Master Brewer, educating others about Kombucha since 2004. Connect with her on Google +