Things You'll Need:
3 quarts filtered water
1 cup sugar. Regular refined white sugar or organic cane sugar works fine. You can experiment with other fermentable sugars, like corn sugar. Many brewers prefer organic, if available. It is possible to use honey instead, but SCOBYs originally matured on sugar will not work well with honey, and the fermenting process may take much longer.
4 or 5 tea bags of organic Tea. Tea bags or loose leaf teas will work. Experiment! Many teas will work: green, black, echinacea, and lemon balm.
A kombucha "mushroom" mother, also called a SCOBY, for Symbiotic Culture of Bacteria and Yeast. If you can't find or don't want to buy a SCOBY, you can make one by buying commercial kombucha and leaving it out (covered, in a warm dark place as described below) for a couple weeks.
1/2 cup of already made Kombucha as a starter, or vinegar if you don't have that. This is to add acidity to the brew, so it's possible that something like pure cranberry juice might also work.
4 quart pyrex bowl, wide-mouth glass jar, or other container. A heavy, food-grade glass jar or large glass Pyrex container is your best bet. NOTE: If you use plastic, metal, ceramic or non-food grade glass containers to make Kombucha - they may (and will most likely) leach toxins, such as lead. If you use a glass container that is too thin, it may fracture when pressure builds inside as the kombucha effervesces.
Instructions:
Wash your hands very well (hot water and soap, for at least 30 seconds under running water). Use of non-latex gloves is also recommended, especially if touching the culture directly.
Fill up your pot with 3 liters (3.1 quarts) of water and put the stove to high. Boil water for at least 5 minutes to purify water, especially if your water supply is chlorinated.
Add 4 or 5 tea bags. According to taste, you may remove tea immediately after brewing, or leave them in for the next two steps.
Turn off heat and add 1 cup sugar (for about three liters of water). Sugar will start to caramelize if water continues to boil, and you don't want that to happen.
Cover and let tea sit until it is room temperature, around 75ºF/24ºC will do. It will seem to take a long time to cool, but adding the cultures when it is too hot will kill them.
Alternatively, you can boil 3 quarters of filtered water. Add the sugar and simmer until all the sugar is dissolved. Then, remove the pot from the heat and add the tea bags. Let them steep for as long as it takes for the water to cool - approximately two hours. Remove the tea bags.
While it is cooling, pull out your pyrex bowl, wide-mouthed glass jar, or other container and wash it well in the sink with very hot water, rinsing thoroughly. If you don't have much extra water for cleaning and rinsing, put 2 drops of iodine into the bowl, add a bunch of water, and swirl it all around to sanitize. Rinse out bowl, cover, and keep waiting.
When the tea is cool, pour it into the bowl (or whatever container you are using) and add the starter tea, which should constitute about 10% of the liquid. Using about a 1/4 cup of vinegar per gallon of tea also works, it tastes just a bit different, though.
Gently put the SCOBY into the tea, cover the top of the container with the cloth, and secure it tightly with rubber band. If you are using a bowl, you can place a piece of plastic wrap with holes punched in the top over the bowl.
Now place the bowl, covered, in a warm dark place where it won't be disturbed. Be sure that insects and dirt cannot fall into the mixture or it will contaminate it. Temperature should be consistently at least 21ºC or 70ºF. 30ºC or about 86ºF is best if you can manage. Lower temperatures will make it grow slowly, but below 70ºF makes it more likely that unwanted organisms will start growing too.
Wait about a week. During this time, you can check on the tea periodically if you like.
Here's what to look for:
The culture will sink or float or do something in between, it doesn't matter. You should see, at some point, a new layer of culture growing on the top. Eventually, it will likely form a film covering the whole top of the tea. It may look strange and discolored, but don't worry, it's probably not moldy. Mold that grows on kombucha looks like the mold that grows on bread - fuzz and all. If it's turning black, discard the tea and get a new cake.
When the tea starts to get smelly like vinegar, you can taste it. The best way to pull a sample is with a straw. Don't drink directly from the straw, as backwash may contaminate the tea. Dip the straw about halfway into the tea, cover the end with your finger, pull the straw out and drink the liquid inside.
Brewed kombucha looks fizzy and tastes sour. If you can still taste the tea, it's not done yet. If it tastes right, then you're ready for the next step.
If not, just keep waiting and sampling every couple of days until it is ready. Don't be impatient. If you move on too soon, it will taste funny, or perhaps too sweet.
The tea is ready when the mushroom has grown a second spongy pancake. Use that to make more tea, or give it away to friends.
When the tea is ready:
Make a new batch of regular tea the same way you did before (steps 1 thru 7, above). Allow to cool.
Bring the container of newly fermented tea into the kitchen, take plastic wrap or cloth off top.
With clean hands (and non-latex gloves if you have them), gently remove mama and baby cultures and set them on a clean plate. Note that they may be stuck together. Pour a little of the kombucha on them to keep them protected.
Using a funnel, pour your finished, newly fermented tea into storage container(s). Fill it all the way to the top. If you don't it will take forever to get fizzy. If there isn't enough, you can either get smaller containers or fill the rest with regular tea. Only do this if there is only a slight gap, though, or else you risk watering down the tea. Another option is to fill it with juice to give it flavor. Fresh pressed is best, of course, but regular works too. Only do this after it's in the container, though. You don't want to contaminate your next batch, since you will...
Leave about 10% of old tea in the glass jar as starter tea. This keeps the pH low to prevent mold and things from growing while the tea is getting started. This insures that the fresh tea solution is acidic enough to combat any foreign molds or yeast.
Pour the new tea in, and put the culture back in, cover, etc. You may use each layer of culture to make a new batch of tea; some recommend using the new layer of culture and discarding the old one. It is not necessary to put both layers of culture back into a single new batch; one will suffice.
Cap your jug or bottles of finished kombucha tightly and let sit for about 2 - 5 days at room temperature to get fizzy.
Refrigerate. Kombucha is best enjoyed cold.