How to Grow a SCOBY From Scratch

You can grow your own SCOBY at home. The most reliable way is to start with a bottle of raw, unpasteurised, unflavoured kombucha, which already carries the culture, and let a new layer grow on sweetened tea. In a warm spot this can take about 10 days. At ordinary room temperature, expect several weeks.

What you need

500 ml (2 cups) raw, unflavoured kombucha. If you can, pick a bottle with visible strands of culture floating in it.
250 ml (1 cup) filtered or de-chlorinated water, divided
1 black tea bag
15 g (1 tablespoon) white sugar
A wide glass jar, about 4 litres (1 gallon) and no taller than about 20 cm. A wide, shallow vessel gives the new SCOBY a large surface to form on.
A tightly woven cloth or paper coffee filter, and a rubber band
A thermometer (helpful, not essential)

On water: chlorine in tap water can slow the culture. Leaving water to stand overnight lets chlorine escape, but it does not remove chloramine, which some water supplies use. If you are not sure, use filtered or bottled water.

Step by step

Clean the jar. Wash it in hot soapy water and rinse well. Some brewers finish with a rinse of white vinegar.
Make a concentrated sweet tea. Bring about 60 ml (¼ cup) of the water to the boil. Stir in the sugar until dissolved, add the tea bag and steep for 10–20 minutes. Remove the bag without squeezing it, as squeezing can make the tea bitter.
Top up and cool. Add the remaining 190 ml of cool water. Let the tea cool to below 32°C (90°F). Hot tea above about 35°C (95°F) can damage the culture, so check with a thermometer if you have one.
Add the kombucha. Pour the cooled tea into the jar and add the 500 ml of raw kombucha.
Cover it. Fasten the tight-weave cloth or coffee filter over the opening with the rubber band. Fruit flies can get through loose weaves such as cheesecloth or muslin, so choose something tight. See what to cover your kombucha with for options that work.
Leave it still. Put the jar somewhere warm, around 22–27°C (72–80°F), out of direct sunlight. Moving or swirling the jar can break up the thin new layer, which then re-forms in pieces.
Look, don’t poke. Within a week or two, a thin cloudy-white film should appear on the surface. At first it may look see-through or patchy. Lift the cover only when you need to look.

How long it takes

Temperature matters most:

Warm, around 27°C (80°F): about 10 days for a usable layer, in one warm, controlled method.
Ordinary room temperature: often 3–5 weeks, and sometimes longer.
Cool room: several weeks to two months. A heating pad can close the gap in winter.

A SCOBY is ready when it is thick enough to lift (roughly 1 cm, or ½ inch), creamy white and opaque rather than clear. If it is still thin or see-through in places, cover it again and give it a few more days.

Using your new SCOBY

When the layer is ready, the liquid underneath will be quite tart and vinegary. Start your next batch with the new SCOBY plus 250–500 ml (1–2 cups) of that liquid.

For the first few batches:

Brew small batches. BBC Good Food suggests 1–1.5 litres of water, 3–4 black tea bags and 75 g of sugar for a new SCOBY.
Use about 10% of the new batch as starter liquid, taken from the top of the previous brew.
Your leftover sour liquid will be very tart. Dilute it with lightly sweetened tea before bottling, or use it in salad dressings.

Can you start a SCOBY from scratch?

Yes, in three main ways:

From a bottle of raw, unflavoured kombucha. This is the method above and is usually the most reliable.
From raw apple cider vinegar. Raw vinegar with a visible mother can grow a vinegar mat. It behaves a little differently, so see our guide to making a kombucha SCOBY from apple cider vinegar.
From plain sweet tea, with no starter. Microbes from the air do the work. This is the slowest route. One guide reports about two months before the layer thickens, and open-air brewing gives mold more chances to take hold.

If you can get a SCOBY or a bottle from a friend or a local brewer, that is the simplest start.

Choosing a bottle

Not every bottle works. Look for:

“Raw” or “unpasteurised” on the label. Pasteurised drinks have been heated, which can stop the culture.
Unflavoured. Fruit, herbs and essential oils can slow things down and may not suit a first ferment.
Visible strands or sediment, if you can see them. They suggest live culture.

Some preservatives can also get in the way. For more on shop bottles, including GT’s and flavoured kombuchas, see growing a SCOBY from store-bought kombucha.

What to avoid

Flavoured or herbal teas in the first brew. Keep the SCOBY on plain black tea, sugar and water. Flavour the bottle later.
Honey. It brings in different yeasts and bacteria. Jun, a different ferment, uses honey, but it is not kombucha.
Artificial sweeteners. The culture can’t feed on them.
Metal containers. Use glass or food-grade ceramic. Plastic and most metals are not recommended.
Dried or refrigerated SCOBYs. Dried SCOBYs often disappoint, and refrigerated ones are slower to wake up.

Troubleshooting

Slow growth. Check the temperature first, since cool rooms slow the culture a lot. Then check the starter. Too little starter liquid is a common cause.
The SCOBY sinks. Usually normal. See why does my SCOBY sink?.
Fuzzy spots. Throw the batch out. See is it mold or a healthy SCOBY? to tell the difference.
Fruit flies. Tighten the cover. If flies have laid eggs in the brew, throw the whole batch away.

Caring for your SCOBY

Keep it in starter tea at room temperature. Store it in a covered jar of kombucha, out of direct sunlight, with some airflow. Many brewers call this a “SCOBY hotel”. Keep it out of the fridge.
Feed it occasionally. A SCOBY can rest for a few weeks in starter tea before it needs attention. Check it every few months and top up the liquid if it is getting low.
Retire it when it’s done. Stop using a SCOBY when it dries out, goes mushy or loses its firmness. Some brewers eat old ones, so read whether eating kombucha SCOBY is good for you before you try.

How many times can you use a SCOBY?

Many brewers get several batches from one SCOBY. BBC Good Food suggests composting one after eight or more batches, while others keep going longer. A firm, healthy SCOBY can often keep working. To learn what the mat is actually made of, see what the ingredients in a SCOBY are.

FAQ

Is a cloudy white layer normal?

Yes. It is usually the start of a new SCOBY and a sign that the brew is fermenting. Leave it alone.

Are brown strands normal?

Yes. Brown or tan strands hanging from the SCOBY or floating in the liquid are yeast colonies, a normal part of fermentation. You can strain them out of finished kombucha if you prefer.

Does the SCOBY have to float?

No. A SCOBY can float, sink or sit at an angle and still ferment the brew. See why does my SCOBY sink? for what to check.