The mentor
Time isn't a setting.
Every recipe says «14 days». None of them knows your kitchen sits at 19 °C in January and 27 °C in August, or that your starter has been in good shape for three months. The Fermenty mentor doesn't hand you a number of days: it works out your window from your conditions, moves it when you taste, and learns from every batch you close.
Free, no sign-up · The free plan includes the whole mentor inside every batch
Why 14 days means nothing
The same recipe, two different results
Fermentation doesn't count days, it counts temperature. For every 10 °C your kitchen rises, the microbes work twice as fast. Which means the same kombucha, with the same tea and the same sugar, can be at its prime on day 6 in August and on day 11 in January.
That's why notebooks aren't enough, and why fixed recipes fail exactly when it matters most: the day you have to taste. A number written on a blog can't know where you live.
How it works
Three things to ask, and it knows
1 · What you want
Mild, balanced, strong. You choose with a phrase, and if you'd rather fine-tune it by hand, you can.
2 · Where it ferments
Your kitchen's temperature and the volume you're making. It's what matters most, and it's what no recipe ever asks you.
3 · What goes in
The tea, the sugar, the starter, the fruit. Each one changes the calculation — fruit brings sugars that are attacked straight away, and that brings the fizz forward.
And what it gives back
The exact amounts for your volume, a window instead of a date, the warnings that matter and — this is what makes it different — the reason why. When the mentor changes an amount, it tells you what changed and in exchange for what.
I've brought the sugar down from 70 to 62 g/L because the fresh cherry brings its own; if you'd rather call it yourself, put it back up and I'll recalculate.
The company it keeps
What happens between the first day and the glass
Day 0 · You formulate
«With 6 litres at 21 °C and this starter, that's 420 g of sugar and a window between day 7 and day 9.»
Day 4 · Going well
The tea still leads the smell; at 21 °C your window doesn't open before day 6.
Day 6 · You taste, and the window moves
If it already tastes more of cider than of sweet tea, you're two days ahead of plan: look again tomorrow.
Notice: the window moved inside the batch, not between batches. That's what following along means.
Day 7 · It opens
It smells of apple and no longer of tea: it enters its window between today and Thursday.
See the batchDay 9 · You close it and rate it
«It came out as you expected, and that teaches something too: next time I'll start from 7-8 days instead of 7-9.»
That last step is the one almost nobody takes and the one worth most. Closing a batch and saying how it went is what turns a general prediction into yours.
How it learns
Inside the batch, and between batches
Inside the batch (hours and days)
You taste, you say how it is, and the prediction shifts. If your batch is running faster than expected, the window moves up that same afternoon. You don't have to wait until the end for it to be useful.
Between batches (months)
Every batch you close and rate teaches it two things: how fast your kitchen ferments, and what you call «at its prime». In time, the windows stop being the general ones and become yours.
That last part is what Fermenty Pro includes. See the plans
Uncalibrated
…it enters its window between day 6 and day 9.
Calibrated
…between day 6 and day 7, because your kitchen runs fast.
Where the numbers come from
A model that lets itself be argued with
Always a range, never a day
If someone gives you the exact day, they're either lying or they haven't done the maths. A window is the honest answer: it says when to start tasting and when it goes past.
A floor that isn't negotiable
Kombucha can't be pushed below five days, because it isn't a speed: it's a sequence — the yeasts first, the acetic bacteria after. If the numbers came out sooner, the mentor doesn't pad the sugar to cover it up. It tells you what will actually happen.
Safety warnings are never charged for
Pressure in the bottle, alcohol nearing the legal limit, margin running out. All of that is on the free plan and it's staying there.
It comes from real batches, not from a blog
The model is anchored in fermentations measured over years, not in a recipe copied from somewhere else. And it's built so a single data point can knock it down: if it predicts four days where it never went below six, it's the model that's wrong.
The model learns from kitchens, not from books
It knows ours already. It doesn't know yours. If you've been fermenting a while and you'd like your way of doing it to feed the model, we're looking for founders: you ferment, you close your batches, you tell us how it went, and you get Pro free for as long as the programme runs.
I want to be a founderTo be clear
Three things you won't find here
It isn't a chatbot.
It doesn't generate text or improvise advice. It's a calculation: same conditions, same result, and where every number comes from can always be explained.
It isn't a timer.
A countdown knows nothing about your kitchen. Here the date moves when conditions do, because that's how fermentation actually works.
It won't promise you health.
We ferment because it tastes good and because it's a fine craft. What science says about fermented food and health we cover on the blog, without hyperbole and without selling miracles.
When you see this seal, the mentor is speaking
What the jar carries is a prediction, not a fact. It can move when your conditions change — and that's exactly the idea.
Try it with your own kombucha
Put in your temperature, your sugar and your starter and see what window comes out. No account, no email needed.