Need it now?
Fastest fermentation
Warms to peak fast, then switches to cold storage on its own.
StartRight after feedingPeakAlertAfterChills automatically
Let it ferment while you sleep
- Funded by 101 bakers on Kickstarter. Every one delivered.
- Built in small batches. 30 units a month.
- Ships November 30 when ordered now.
They said it would get easier. So why am I still so busy?
Every kitchen and every starter is different,
so there's no one right answer.
To find your own answer,
you had to do the work yourself.
Introducing
The more you use it,
the more it fits you
SourFriend Pro
- Learns,
Feed at the same ratio 3 times,
and it learns your starter's pace. - Decides,
It decides when to ferment
and when to chill on its own. - Adapts
It predicts the finish
and has it ready on time.
Not a lucky ferment, but a reliable one
Time to peak · predicted vs actual at the same feeding ratioActual SourFriend predicted
Run 1 error1h 48m
Run 3 error54m
Run 10 error10m
Source: SourFriend internal test results
Beta tester reviews
Stories from the people who met SourFriend first.
I used to set an alarm and move it to the fridge at dawn. Now I set Delayed Mode before bed and just sleep. In the morning I take it out and it's ready for dough.
The first few times the prediction was a little off, but the more I use it, the closer the alert time gets to when it actually peaks. Now I just trust the alert and plan around it.
Every summer, throwing out over-fermented starter was a chore. Now it cools itself even on hot days, so my starter doesn't turn sour. The most convenient part is that it switches to cold storage once the peak has passed.
What $699 covers
One device for the whole starter routine, from feeding to cold storage.
- Warms and cools on its own
One device from feeding to cold storage. No moving jars to the fridge at night.
- Four sensors
Tracks starter height, inside temperature, room temperature and humidity.
- App Plan included, no time limit
App-only users need Pro (US$7.99/month) for Plan from 2027. Connect SourFriend Pro and you use Plan at no extra cost, with no time limit.
- Up to 4 years of warranty
2 years from purchase, plus 2 more when you register within 30 days.
In the box
SourFriend Pro
Tritan container (890 ml)
USB-C cable
Power adapter (DC 12V / 3A)
Buy without worry
- Change your mind?
Full refund anytime before shipping.
- 30-day returns
Return unused items within 30 days of delivery.
- Shipping & duties included
Delivered to the US by DHL Express.
- Defects are covered
Separate from returns, defects are covered by the warranty: 2 years, plus 2 more when you register within 30 days.
fermenting in oneRests cold overnight,
wakes up in the morning.
better each useLearns your pattern at
the same feeding ratio.
Until it syncs
with your starter
at a glanceSee your starter's
status in the app.
5 ways SourFriend builds
your own fermentation environment
01
Auto warm/cool switching
Between chilled and room temperature, set automatically with no second-guessing
02
Built-in AI learning
The more you use it,
the better it fits your routine
Repeated fermentation at the same feeding ratio · Peak prediction error (min)
0306090
Learning phaseAfter run 3 · Delayed Mode
136912
Quick Mode runSource: SourFriend internal test results
03
Real-time status tracking
See your own formula
for success, right in the app
04
Perfect-timing alerts
From feeding to fermentation complete,
catch the right moment
7:02
Tuesday, November 3
SourFriendnow
Peak is nearTake it out now and it's ready to use in your dough.SourFriendYesterday 9:40 PM
Time to feedDay 6 in storage. Please feed it once this week.05
Tritan container
Only a layer of clear Tritan touches your levain
01
Chill to rest, warm to wake
Through every season,
it moves between cooling and warming on its own.
* Cooling performance may vary with the ambient temperature.
02
Easy to use
Need it now?
Prep for tomorrow,
ready on time
Rests overnight and wakes at your set time. At the same feeding ratio, the timing gets sharper the more you use it.
TonightFeedEarly morningWarms up automaticallyTomorrow 7 AMPeak
Time for
a short break
Up to 14 days chilled, no feeding needed. 1–2 feedings wake it back up.
StartNo feedingBack in use1–2 feedings
Start with one dial
Turn,
Press, and you're underway
It speaks in color
Yellow means warm fermenting
Past double, a green dotted line
Green light means now
Blue means chilling to slow down
03 · Why we built it this way
Why 890ml?
Sized for the levain you use at home in one go: 150–300ml.
Even when it triples, it won't overflow, and it tracks the rise accurately.
Right after feeding
Not a starter. A companion
Designed so you can check on it standing up.
No need to hover over the device
Supports both Bluetooth and Wi-Fi.
Check its status and control it even when you're away from home.
Real-time monitoringSee your starter's rise, live
Fermentation reportPeak and progress at a glance
Remote controlWake it or stop it from anywhere
Success you understand
Download it from your app store now.
Plug in, load up,
turn the dial. Done
Before you buy
Will it work with my starter?
Yes. White, whole wheat or rye, it works with the starter you already keep. Put 150–300 ml in the Tritan container.
On the first few runs, timing starts from default values for how starters usually rise. Each time you feed at the same ratio and run Quick Mode, SourFriend measures how fast and how high your starter actually rises, and adjusts. After three runs, the timing follows your starter, not the defaults, and it keeps getting sharper the more you use it.
If you change your flour or feeding ratio, run Quick Mode three more times and it learns the new pattern the same way. Learning works when the device is connected to the app.
How accurate is the peak prediction?
It gets closer with every run. In our internal tests at the same feeding ratio, the prediction was off by about 1 hour 48 minutes on the first run, 54 minutes on the third, and about 10 minutes by the tenth.
Your results depend on your starter's condition, feeding ratio and room temperature. So for the first few runs, treat the alert as a guide and check on your starter yourself. After that, SourFriend handles most of the timing for you.
When will I get it?
Orders placed now ship on November 30 by DHL Express. US shipping and import duties are included in the $699.
We build 30 units a month, so orders ship in batches, in the order they come in. If your plans change, you can get a full refund anytime before your order ships.
SourFriend Tech Specs
Size
163 × 280 × 285 mm (6.4 × 11.0 × 11.2 in)
Weight
Approx. 3–4 kg (6.6–8.8 lbs)
Materials and finish
Body: matte white / matte black
Cap: clear Tritan
Controls: rotary dial with built-in LCD
Fermentation jar
Tritan jar
Up to 890 ml (30 fl oz)
100 × 127 mm
Recommended starter amount: 150–300 ml
Temperature control
Automatic heating and cooling with a Peltier module
Temperature range: 5–35°C (41–95°F)*
* The lowest temperature SourFriend can reach depends on the temperature of your room.
Sensors
Fermentation height sensor
Internal temperature sensor
Ambient temperature sensor
Humidity sensor
Fermentation features
Quick Mode
Delayed Mode
Storage Mode
Core fermentation AI: detects doubling and peak, then switches to Storage Mode
Connectivity
Bluetooth LE 5.0
Wi-Fi 2.4GHz (5GHz not supported)
SourFriend app (iOS, Android)
Power
Rated input: DC 12 V / 3 A
Power consumption: up to 36 W
Use the included adapter (for a replacement, a USB PD adapter rated 36 W or higher with 12 V output)
Environment
Recommended room temperature: 5–25°C (41–77°F)
Place in a well-ventilated spot, at least 10 cm (4 in) from walls
Warranty
2 years from date of purchase (plus 2 more years if registered within 30 days of purchase)
Manufacturer
Toasterz Inc.
What's in the box
SourFriend unit
Tritan container
USB-C cable
Power adapter
Beyond levain. For anything that ferments.
SourFriend Pro
$699
US shipping & duties included · Full refund before shipping
Buy now