Fermento
App of the Day
from the creators of 
murmur
Layered
Kombucha is forgiving until you want the same batch twice. A short log is what lets you repeat a good one and work out what went wrong with a flat or sour one.
The log
| What | When | What it tells you |
|---|---|---|
| Tea, sugar, water and starter weights | At the start | How to repeat the batch |
| Starter share of the batch | At the start | Whether there is enough to acidify it |
| pH after adding the starter | At the start | Whether the brew starts acidic enough |
| Room temperature | Daily | Why this batch ran fast or slow |
| pH | Daily near the end | When it reaches the range you want |
| Taste | Daily near the end | When to bottle |
| Bottling date | At bottling | How long it has been building fizz |
The numbers behind it
Fermento's Basic Kombucha template is 8 g of black tea, 200 g of sugar, 3 litres of water and 400 g of starter tea, fermented for seven days.
The limits in Fermento's kombucha plan come from published guidance:
- Starter. At least 10% starter liquid, and a pH of 4.6 or lower once it is added, from the Kombucha Brewers International code of practice.
- Fermentation. A pH of 4.2 or lower within 7 days and never below 2.5, from Pennsylvania and New York guidance. Ireland's Guidance Note 37 gives 4.4 or lower within 7 days, and not below 3.0.
- Bottling. A live drink keeps fermenting in the bottle. In the United States it has to stay below 0.5% alcohol at all times to count as a soft drink.
At home nobody will ask for your records. The same numbers still tell you the brew is on track.
Notes that are quicker than numbers
Some of the most useful entries are observations. Fermento's check-in has quick tags for the common ones: pellicle forming, smells vinegary, tastes ready, bottled, fruit flies and mould.
In Fermento
A brew is a batch with a timeline, a daily taste reminder and readings for pH, temperature and Brix. The SCOBY hotel has a record of its own, so you can see which culture started which batch. See kombucha in Fermento. If you sell it, see the HACCP plan for kombucha.
Updated 11 November 2026.
Questions
What pH should kombucha reach?
The guidance cited in Fermento's kombucha plan differs by place. Pennsylvania and New York guidance asks for 4.2 or lower within 7 days and never below 2.5. The Food Safety Authority of Ireland's Guidance Note 37 asks for 4.4 or lower within 7 days and not below 3.0.
How much starter tea does a batch need?
The Kombucha Brewers International code of practice asks for at least 10% starter liquid. Fermento's Basic Kombucha template uses 400 g of starter tea for 3 litres of sweet tea.
Should I track Brix?
It helps if you want repeatable batches. Brix measures dissolved sugar, so it falls as the brew ferments. Fermento logs it beside pH and temperature.