Can you start a SCOBY from scratch?

Yes. You can grow a SCOBY from scratch using sweet tea and a cup of raw, unpasteurised, unflavoured kombucha. It usually takes around 2 to 4 weeks to form a layer thick enough to use, and sometimes longer. A SCOBY grown this way can be thinner and weaker than one from an established brewer, so use the full amount of starter in your first batch.

What You Need

• Raw kombucha: about 250 ml (1 cup). It must be unpasteurised and unflavoured, with live culture. Check the label, because pasteurised or flavoured kombucha may not work well.
• Sugar: 50 g of plain white sugar for a 1 litre jar. See how much sugar for 1 litre of kombucha for why.
• Tea: 2 to 3 black or green tea bags, with no added flavour or oil.
• Water: about 750 ml, which becomes the sweet tea.
• Equipment: a clean glass jar of about 1.5 litres, a tightly woven cloth or coffee filter, and a rubber band.

Step-by-Step: Growing a SCOBY

1. Clean everything. Wash the jar, pot and spoon in hot water with plain dish soap, and rinse them well.
2. Make the sweet tea. Boil the 750 ml of water, turn off the heat, and add the tea bags. Steep for 5 to 10 minutes for black tea, or 3 to 5 minutes for green. Remove the bags without squeezing them, and stir in the sugar until it dissolves.
3. Cool it to room temperature. The sweet tea should be about 20 to 25 °C before anything else goes in. Heat can damage the live culture in the raw kombucha.
4. Combine. Pour the sweet tea into the jar and add the 250 ml of raw kombucha.
5. Cover and leave. Cover the jar with the cloth or coffee filter and secure it with the band. Keep it at a steady room temperature, roughly 20 to 27 °C, out of direct sunlight. Don’t shut it in a closed cupboard, because it needs airflow.
6. Wait without disturbing it. After a few days you may see small bubbles. A thin, clear or cloudy film forms on the surface and gradually thickens. Over a few weeks it becomes an opaque, creamy white or beige disc.

The new SCOBY is usually ready to use when it covers the surface, is opaque, and is about 6 mm (1/4 inch) thick or more. Don’t rush it. A thin layer that is still growing is better left a few more days.

What a Healthy New SCOBY Looks Like

• A thin, clear or cloudy film at first, which thickens over time.
• An opaque, rubbery white or beige disc once it is established.
• Bubbles under or within the layer, and brown or stringy bits in the liquid. These are normal.
• A disc that sinks, floats or sits at an angle. This is also normal.
• A clean, sour, vinegary smell.

Mould, Kahm Yeast and When to Start Over

Check the surface through the cloth without sloshing the liquid. For a closer comparison, see how to tell mould from a healthy SCOBY.

• Mould is fuzzy or dry, raised, and sits on top in white, green, blue or black. Throw the whole batch away, including the liquid, and start again in a clean jar. Don’t scrape the spots off and carry on.
• Kahm yeast is a flat, wrinkled white film, not fuzzy. It is not mould, but many guides still advise starting again, because it can be a sign of a weak culture.
• A rotten, putrid or chemical smell means the batch should not be used.

If nothing has formed after about 4 weeks, the cause is often a cool room, too little raw kombucha, or raw kombucha that was weak or not fully live. Start again with fresh raw kombucha in a warmer spot.

Using Your New SCOBY for the First Batch

A homegrown SCOBY is often thinner, and its starter liquid is often weaker, than a SCOBY from an established brewer. For your first full batch:

• Use the full amount of starter, which is 500 ml for a 4 litre batch. Don’t reduce it.
• Taste from day 7, and watch the first batch closely for signs of mould or a sharp smell.
• Keep some of the finished kombucha and the SCOBY for the next batch. A homegrown culture often becomes steadier after a few batches.

The full brewing method covers the timing and bottling steps.

Other Ways to Get a SCOBY

• Ask a friend or local brewer. Every batch usually grows a new layer, so established brewers often have spare SCOBYs to share.
• Buy one. You can buy a SCOBY online, or from a health food shop or homebrew supplier, often as part of a starter kit. When it arrives, check that it is moist, not dried out, and free of mould.
• Try a local workshop. Some kombucha courses share SCOBYs with participants.

Keeping Spare SCOBYs

A “SCOBY hotel” is a clean jar with some finished kombucha to keep spare SCOBYs covered and alive between batches.

• Cover the jar with a cloth and keep it at room temperature, out of direct sunlight.
• Top up the liquid if it drops, and check regularly for mould. For timings, see how long a SCOBY can sit in starter liquid.
• Some brewers keep SCOBYs in the fridge for longer breaks. Cold slows the culture, so it may take time to recover. Room temperature in a covered jar is the more common approach for regular brewing.

FAQ

How long does it take to grow a SCOBY?

Usually around 2 to 4 weeks. It can take longer in a cool room or with a weak starter.

Can I use store-bought kombucha?

Only if it is raw, unpasteurised, unflavoured and has live culture. Many commercial brands are pasteurised, which removes the live culture and may stop a SCOBY from forming. Growing a SCOBY from store-bought kombucha covers which bottles to choose.

Is a homegrown SCOBY safe to use?

A healthy-looking SCOBY from a clean setup is generally a good starting point. Discard the batch if you see mould or smell something rotten. Is homemade kombucha safe to drink? covers the warning signs in more detail.

Do I need to buy a SCOBY for every batch?

No. Each batch usually grows a new layer, so you can keep a piece of the SCOBY and some liquid from one batch to start the next. You only need a new SCOBY from another source if the old one is weak, mouldy or lost.