Creating a sourdough starter can feel like alchemy. You mix flour and water, wait for it to bubble, and hope you don’t accidentally grow a sentience that takes over your kitchen.
It’s easy to be intimidated by the process, but when you shrink down to the microscopic level, it stops being magic and starts being simple biology.
We recently released an animated guide to show you exactly what happens inside that jar. If you haven't seen it, watch "Sourdough Starter Explained in a Nutshell" below, and then read on to understand the 7-day journey of your new microscopic civilization.
The Hidden Civilization
A sourdough starter looks like plain dough, but underneath, it is a bustling ecosystem. You aren't just baking; you are a zookeeper for billions of microbes.
Here is the day-by-day breakdown of the war for dominance happening in your jar.
Day 1: The Genesis
When you mix flour and water, you aren't adding yeast; you are waking it up. Dormant organisms—wild yeast and bacteria—are naturally hiding on the bran of the wheat, just waiting for moisture to activate.
Days 2-3: The "False Rise"
You come into the kitchen and see bubbles! Your starter has doubled in size! You’re a natural born baker!
Stop. Don’t get excited.
This is the most common trap for beginners. This early activity is likely caused by Leuconostoc bacteria—impostors that produce gas but not the flavor or rising power you need.
You might notice a smell like old cheese or gym socks. That is normal. This stench is the scent of the battle beginning.
Day 4: The Silent Crash
Suddenly, all activity stops. The bubbles disappear. The jar looks dead.
Do not panic. Do not throw it away.
This "Quiet Phase" is actually a sign of success. As acidity rises in the jar, the environment becomes hostile to the impostor bacteria, and they die off in a mass extinction event. The pH is dropping past 4.0—the safety point where bad bacteria cannot survive.
Your jar isn't dead; it’s just clearing the battlefield for the true heroes.
Days 5-6: The Resurrection
From the silence, the true citizens emerge: Lactobacillus and wild yeast. They thrive in this acidic environment.
Now, we feed. By discarding half the starter and adding fresh flour and water (100g each), you fuel this strong foundation, encouraging the colony to multiply.
Day 7: The True Rise
By the end of the week, your culture should double in size within 4 hours of feeding. It won't smell like socks anymore; it will smell sweet, yeasty, and ripe.
This is the perfect symbiosis. You have successfully cultivated a colony of billions, all working together, just waiting to bake.
Ready to start your own colony?
Grab a jar, some flour, and patience. The biology will do the rest.