How I Make Kombucha

Kombucha is tasty and satisfies the inherent human need for bubbly drinks. I attempted to start some years ago and followed the instructions of a roommate who claimed to know what they are doing but was met with failure and mold cultures I never asked for. At the intersection of grocery inaccessibility and a burning desire to create new low-stakes problems for myself to focus on, I decided to give it another go. Below is my current method assembled from a combination of reading about kombucha on the internet, watching culinary comedian Brad Leone, and talking to my sister who brews a lot of kombucha. If you wish to become a learned kombucha maker you will find much written on the topic, but here I will summarize my current process first in abbreviated form and then with further explanation.

Short notes

unpasteurized unflavored store bought kombucha at room temp for 2 weeks with access to air to develop starter
feeder tea formula is 70g cane sugar + 7g black tea leaves per liter of 76C water off heat and steeped 20min. Brew with half of total water and reserve half until end of brew to immediately have safely cool feeder tea (40C or less).
bottle 60% of master culture at end of cycle and replace with same volume of feeder tea. For expansion either move slowly over several cycles or allow much more time until next bottle/feed.
bottling ratio should be about 16% fruit juice / 84% kombucha to provide flavor and fuel for bottle conditioning.

Longer Explanations

The Initial Culture

Two bottles of GT’s brand kombucha - ‘original’ flavor and unpasteurized only - are poured into a glass jar of sufficient size. Sufficient in this case means “looks about right to me” and more narrow than wide in order to not evaporate off quickly. The jar’s mouth is covered with something that is permeable to air and not bugs. I used 4 layers of cheesecloth and a rubber band, but most sensible things like a coffee filter paper or a cloth will work. Let it sit for about 2 weeks at room temperature to allow the culture to do the things a culture does. Once it has become sufficiently kombucha’d the procedure moves on.

The Jar

I use a really big jar. I think it’s about 10 liters. Your big jar size dictates the throughput of the system. You cannot bottle all the kombucha because you need to leave some kombucha in the jar to make more kombucha. In some situations this is referred to as backslopping. I am pretty loose about this but it seems like a ratio of about 2 parts old kombucha and 3 parts new tea is good. This means you get about 60% of your jar’s volume to drink for every full cycle of the culture. For me that means I’ve got a half liter bottle of kombucha available every day if I want it.

The Tea

I use some no-name black tea. People will tell you that you cannot just feed any random tea to your kombucha because it might have random stuff that will kill your culture. I have not tested this and cannot speak to it. I just buy the loose leaf black tea that is like $12 for a 1.5 kilo bag and I’ve had no problems. My method for the tea I feed my culture with is as follows:

Heat 50% of the water in stock pot to 76C
Turn off heat
Add 7 grams of black tea leaves per liter of water into the pot, stir briefly to disperse
Set timer to 20 minutes
As the timer goes off, add 70 grams of sugar (white cane sugar, but sometimes I get the hawaiian turbinado and use that) to the tea and stir to dissolve
Add the second 50% of the water to the mixture
Strain the now-sweet tea into an empty container and hold it there until the temperature is at or below 40C

At this point it should be added to the main jar with the culture.

The Wait

The cycle time until bottling is variable depending on local weather, the particulars of the state of the culture, your personal tastes, and probably other things I am not taking into account. I see times of 12-18 days to get to where I want to be, but you should carefully taste and smell things to track progress. I’ve tried monitoring pH but for personal consumption this feels like an unnecessary step and it ends up being more work than just pipetting some off to see if it tastes good.

Bottling

I use an auto siphon and a bottling stick thing with a valve, both are common and cheap online. You don’t have to use them but it’s really handy. One way or another you need to stir up the big jar and then move the liquids into bottles. Because the kombucha will build pressure when contained, the general consensus is that you need to be sure to select bottles that are of adequate strength. I have not had one explode but I’ve also only used flip top style bottles that are expressly specified for kombucha.

When bottling, I add 80mL of juice to a half liter bottle prior to topping it off with kombucha. The idea is that the sugars in the juice provide more fuel for the culture to consume and create carbonation. This is called bottle conditioning and is also done when home brewing beer.

Wait Part 2

Every source I’ve got says kombucha should be fizzy about 4 days after being trapped in a sealed bottle and left out at room temperature but my experience has differed greatly. I tend to wait 7-10 days in order to have the level of carbonation I’d like, and your result may be something else entirely. Once carbonation is achieved, the bottles can go in the fridge. I have not seen clear guidance or answers on what would happen if you leave it out instead, and I have found no issue with the bottles sitting out for a couple of weeks before going in the fridge. As with most of this process, there is a strong element of personal taste and whimsy.