The period of 8 - 12 days is given merely as a guide. The Kombucha culture needs a warm and quiet place and should on no account be moved. Light is not necessary. The culture also works in darkness. The culture may be damaged by exposure to bright sunlight.
Half shade is better.
It is the combination of these processes which gives the Kombucha beverage its characteristic flavor. The infusion is at first sweet but this sweetness disappears as the sugar is broken down. At the same time an acid flavor begins to develop as a result of the activities of the bacterium, so there is a transition from sweetness to sourness. If a slightly sweet drink is preferred, the fermentation has to be stopped earlier. For a dry or slightly acid flavor it has to be continued longer.