Homemade Kombucha

• 7 cups, divided water (3 cups to brew the tea and 4 cups cold; filtered, or boiled and cooled)
• 4 tsp loose black tea (or 4 plain black tea bags; avoid flavored teas such as Earl Grey, whose oils can harm the culture)
• 1/2 cup (100 g) cane sugar (plain sugar is food for the culture, and most of it is consumed; honey’s antimicrobial properties can interfere)
• 1 cup (240 mL) unflavored kombucha (starter liquid from an earlier batch, or plain unpasteurized store-bought; its acidity (pH 4.0 or lower) protects the new batch)
• 1 kombucha SCOBY (from a trusted brewer or supplier)
• 1 pack pH test strips (range covering about 2.5 to 4.5)

Instructions

1. Wash your hands, then wash a 1-gallon (or at least 3-quart) wide-mouth glass jar in hot, soapy water and rinse it several times until no soap remains. The batch is about 8 cups with the starter, so a smaller jar would overflow. Do not use glazed pottery, crystal or metal containers: kombucha is acidic enough to pull lead and other metals out of them.
2. Bring 3 cups of the water to a boil, turn off the heat, add the tea, and steep for 5 minutes. Remove the tea, then stir in the sugar until it dissolves completely.
3. Pour in the 4 cups of cold water, then let the tea cool until it has dropped below 85°F (29°C), which can take an hour or more. Do not go further until it has, because hot tea kills the culture.
4. Pour the sweet tea into the jar, then add the starter liquid. Dip a pH strip into the mixture: it should read 4.2 or lower. If it is higher, stir in another 1/4 cup of starter.
5. Slide the SCOBY onto the surface with clean hands (it may sink or float). Cover the jar with a tightly woven cloth or coffee filter held by a rubber band to keep out fruit flies, and leave it at 70 to 78°F (21 to 26°C), out of direct sun and undisturbed.
6. Start tasting after 7 days with a clean spoon or straw. Ferment for 7 to 14 days, until it is pleasantly tart and no longer syrupy, with a pH of 4.2 or lower. Brown strings and a cloudy base are normal; fuzzy mold on the surface is not, so discard the whole batch, SCOBY included, if you see any.
7. Lift the SCOBY out with clean hands and set it in a clean jar with 1 cup of the finished kombucha, ready for your next batch. Pour the rest into clean glass bottles, cap them, and refrigerate. Drink within 2 to 4 weeks.

Tips

• Start with a small glass, about 1/2 cup. The diabetes pilot used 1 cup (240 mL) a day, and there is no evidence that more is better.
• Flavor it in the glass: a splash of juice or a slice of ginger when serving. Adding sugar or fruit to the bottled drink can restart fermentation, shift the acidity and build pressure, so skip the second fermentation.
• Warmth speeds the ferment and makes it more vinegary. In a cool room it can take two weeks, so taste daily from day 7 rather than trusting the calendar.
• Finished kombucha keeps fermenting slowly in the refrigerator, so open bottles slowly over the sink: they can foam and build pressure.

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