Rehydrate in sweet tea with a generous splash of starter liquid (unpasteurised, unflavoured kombucha) and give it 2–4 weeks across a couple of short batches before judging it non-viable. A very thin new film on top is a good early sign.

Keep brewing on schedule and use a generous amount of starter liquid each batch. Thickness usually builds noticeably by the third or fourth brew.

Leave it alone. A new culture layer will form at the liquid's surface on its own timeline, whatever the old SCOBY is doing underneath.

No action needed. See "Is it mould?" below for how to tell this apart from genuine contamination if you want a clearer picture.

Try one fresh batch with a new SCOBY layer from a hotel or a trusted brewer before retiring the old one — often only the top layer needs replacing, not the whole stack.

Fuzzy, raised, dry spots: discard the entire batch, the SCOBY, and the liquid, and start fresh with clean equipment and a new culture. Anything smooth, wet, or stringy with a normal tangy smell: no action needed.

Cover the jar with a tightly woven cloth (not cheesecloth, which has gaps too large) secured firmly with a rubber band, and keep the brewing area away from fruit bowls or compost.

Keep hotel SCOBYs in their own separate container with their own tea, use separate utensils for each vessel, and isolate or discard immediately if any one culture shows true mould.

Use plain black or green tea as your base, unflavoured and without added oils. Save herbal or flavoured infusions for the second ferment instead, added after the SCOBY is removed.

Let sweet tea cool fully to room temperature before adding the SCOBY and starter liquid — this is one of the easiest steps to rush and one of the most consequential to get right.

Make sure sugar is fully dissolved while the tea is still hot, before cooling. Adjust final sweetness mainly through ferment length — shorter ferments leave more residual sugar — rather than by changing the starting amount.

Extend the first ferment by a few more days and taste-test through a straw daily from around day 7 onward. As a rough guide, first ferments take 7–14 days at room temperature — longer in cooler weather.

Pull the batch a few days earlier next time, and note the exact day it tasted right so you can repeat it. An overly sour batch isn't wasted — it makes a strong starter liquid for your next brew, or a base for a salad dressing.

Keep one variable fixed at a time (same jar spot, same starter ratio) for a few batches while you dial in your preferred timing, then adjust one thing at a time from there.

If the smell is faint and fades by the end of the ferment, no action needed. If it's strong, persistent, or paired with visible fuzzy growth, treat it as a contaminated batch — see "Is it mould?" above.

Bottle into airtight swing-top bottles with a little sugar or fruit juice added for extra fuel, and leave sealed at room temperature for 2–5 days before refrigerating. Check pressure by gently pressing the lid — it should feel firm, not springy.

Use thick-walled bottles rated for pressure, shorten the second ferment, and burp bottles once a day by briefly cracking the seal over a sink. Refrigerate as soon as carbonation feels right — cold slows the process right down.

Stir the batch gently before bottling so yeast and sugar are evenly distributed, and check swing-top gaskets aren't worn or letting gas escape.

Use plain glass for the fermenting vessel, food-grade plastic only if labelled safe for acidic liquids, and avoid metal or unknown ceramic glazes for anything in prolonged contact with the brew. A brief stir with stainless steel is fine.

Match jar diameter to SCOBY size where possible, or size down to a narrower vessel until the SCOBY grows to fill it.

A fine nylon mesh strainer or a funnel lined with a clean cloth catches more sediment than a standard kitchen strainer. Straining is optional — some brewers prefer to leave a little sediment in for a more traditional texture.

If you're avoiding alcohol entirely, keep ferments shorter, refrigerate promptly once bottled, and be mindful that longer or fruitier second ferments tend to have higher levels. If this matters for your situation, check with your healthcare provider.

If you're caffeine-sensitive, brewing with green tea or a shorter tea-steeping time can reduce the starting caffeine level. Decaffeinated tea is generally not recommended as a base, as the culture relies on nutrients that some decaffeination processes remove.

If you're pregnant, immunocompromised, or have a condition affecting your gut or immune system, it's worth checking with your doctor before drinking homemade kombucha regularly. This is general information, not individual medical advice.

Brew smaller batches, extend the gap between brews, or share bottles and spare SCOBYs with friends or your local fermenting community.

Keep it in a jar covered the same way as an active brew, with enough sweet tea to fully submerge the SCOBYs, and top up or refresh the tea every 4–6 weeks so it doesn't run out of food.

Start with batch brewing to learn your timing and taste preferences, then consider switching to continuous brew once you're ready to simplify the routine.

Extra SCOBYs can be composted, shared with someone starting out, dehydrated for storage, or used in cooking (some people blend them into smoothies or use them as a base for homemade fruit leather).