My kitchen is pretty cold in winter since it faces north and it takes forever for kombucha to ferment all by itself. I did some internet reading and found that there are several ways to keep the tea warm enough to encourage the scoby without being too warm. The method I use is a reptile tank warming pad (available in 'most any pet store) that would normally go underneath a terrarium. I put it on the kitchen counter, put a pot holder down and put the glass jar containing the tea and scoby on top of it. A towel would probably work just as well between the warmer and the jar, if not better. It still takes about eight to ten days, but without it, it'd be two weeks at least.

I used green tea in mine.

Anhata
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