4. Cover the jar with a thin cloth (like cheesecloth) and secure it with a rubber band. This will prevent insects or debris from getting in. Store it away from direct sunlight and somewhere moderately warm (70F-80F is ideal). Allow to ferment for 2-4 weeks depending on how sour/strong you like your kombucha – I recommend smelling or tasting it every few days after the two-week point. I generally brew mine for 3 weeks, but that can vary based on season and how warm it is in our house.