Temperature control

Kombucha Basics: Temperature · Watch on YouTube

Temperature strips

Ange likes simple, affordable temperature strips* stuck to the outside of her brewing vessels to monitor the average room temperature around them. They work like a mood ring or a glow-in-the-dark sticker — no batteries, no space taken, and you can check them without opening the vessel or messing with your SCOBY.

Minor quirks: sometimes 2–3 sections "light up" at once, or none light up clearly. Running a hand along the strip usually re-activates it so the correct temperature glows brightest — and if two adjacent numbers glow, the real temperature is right between them. Kombucha doesn't need precision, so these work just great.

Accommodating for low temperatures

It's not always possible to keep the perfect range, and that's okay — kombucha is fairly hardy as long as you know what to watch for and can overcompensate for the weak spots. In winter, lower temperatures make the yeast and bacteria less active: fermentation takes longer, and if the brew doesn't acidify fast enough, mold becomes possible. (Once your brew is acidic enough to bottle, mold is really unlikely — your bottles will just carbonate slower.) When the weather turns colder:

• Use extra starter tea — try doubling your usual amount. It acidifies the brew and gives it a head start: less susceptible to mold, shorter fermentation cycle.
• Wrap string lights (Christmas lights) around your vessel — all the way around, not just the bottom. Heating only the bottom over-stimulates the yeast that settles there, and an over-abundance of yeast means a brew that doesn't taste right and a lot of back-pedaling to rebalance.
• Heating/seedling mats under the vessel: other homebrewers suggest them, but Ange doesn't recommend the under-the-jar approach for the same bottom-heat yeast issue. If you use one, wrap it around the vessel for even heat distribution. (A purpose-made wrap-around brew heater solves this nicely.)
• Move vessels near the heater or furnace.
• Have patience. Sometimes your brew just needs to do things on its own time. As long as there's no mold, it's trying its hardest to acidify for you.

Accommodating for high temperatures

In summer, everything speeds up — including F2 carbonation, so your bottles may need less time at room temperature before the fridge. You don't really have to worry about killing your SCOBY unless the liquid gets above 100°F. If it's heading that way:

• Move the vessel to the coolest, darkest spot in your home — a closet is OK in the heat if you take it out at night when things cool down.
• Keep it near an air-conditioning vent.
• In extreme cases, refrigerate the brew vessel for a few hours at a time to bring the temperature back down, then return it to room temperature.

There's less you can do against extreme heat, so mostly: shorten your fermentation time and bottle sooner, before the brew gets too acidic. And if a batch does get away from you — no worries, don't throw it out! Overly acidic kombucha is fantastic super-strong starter tea for future batches, or you can balance it with sweet tea or fruit flavorings and bottle it up.

On this page, you'll find some affiliate links to sources where Ange has purchased the ingredients/materials she uses. She may get a small cut of Amazon's profit for finding + recommending them to you — it won't cost you any more than you'd normally pay. She went through a lot of trial and error to find low-cost, high-quality options to save us all money. But feel free to purchase from wherever you like!