Same routine for a year. Moved house and the brewing spot is now about 18C instead of 24C. The tea still goes sour roughly on schedule but no new pellicle has formed across the surface in three consecutive batches, and the mother is thin and patchy. Is a missing pellicle a problem in itself or just cosmetic?
Thin patchy growth in a cool room is normal. What would worry me is dry blue-green fuzz sitting on top of the pellicle, which is the one real mould scenario in kombucha, and it mostly happens when the surface is exposed and there wasn't enough starter liquid.
No fuzz, and the surface is fully covered apart from the pellicle itself. Reassuring.
Check starter liquid volume as well as temperature. You want about 10% of the batch from a mature previous one. When I moved house I unknowingly cut mine to about 5% because I'd bottled everything, and the next three batches were sluggish.
Pellicles also stop forming when the culture is very old and there's a stack of them in the jar. If you've got four or five layers, peel the bottom ones off and keep the newest.
@weatherfront_wu · 3w ago · 3 replies
Mostly cosmetic. The pellicle is cellulose the bacteria produce as a byproduct, not the engine. Fermentation happens in the liquid, so a batch that sours on schedule with no new pellicle is fine.
That said 18C is genuinely low and pellicle formation is the first thing to stop, so it's a useful thermometer. If batches start tasting flatter or taking longer, warm it: a seedling heat mat under a towel, a shelf above the fridge, or an aquarium heater in a water bath around the jar. 24-26C is where mine is happiest. Don't just put it in an airing cupboard and hope.
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@keg_line_ken · 3w ago
Heat mat with a cheap thermostat has it at 25C and there's a new pellicle within a week. Good to know it wasn't a sick culture.
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@leaf_litter_lou · 3w ago
Cooler brewing also shifts the balance towards the yeast side, so you get more fizz and less clean acidity. Not a problem, just different.
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