There’s a jar sitting on someone’s counter right now, bubbling away like it has somewhere important to be. That jar holds a living thing — billions of wild yeast cells and bacteria working together to do something humans figured out thousands of years ago: make bread rise without a single packet of commercial yeast. If you’ve ever wanted to join that tradition, you’re in the right place. This guide will walk you through building a sourdough starter from scratch, keeping it alive, and eventually baking a loaf that will make you genuinely proud.
Fair warning: sourdough is not a weekend project. It’s a commitment. But it’s also one of the most satisfying skills you can pick up in a kitchen, and once you understand what’s actually happening at each stage, the whole process starts to feel less like following a recipe and more like having a conversation with your dough.
What Is a Sourdough Starter, Really?
Before you mix a single gram of flour, it helps to understand what you’re actually creating. A sourdough starter is a fermented mixture of flour and water that captures wild yeast and lactic acid bacteria from your environment. These microorganisms eat the sugars in the flour, produce carbon dioxide (which makes your bread rise), and release acids that give sourdough its characteristic tangy flavor.
Every starter is different. The wild yeast on your hands, in your kitchen air, and already present in your flour will colonize your starter and make it uniquely yours. That’s why a starter from San Francisco tastes different from one made in Vermont — different microbial communities, different flavor profiles. Yours will be a one-of-a-kind culture shaped by where you live.
What You Need to Get Started
The good news is that the equipment list is short. You don’t need anything fancy.
- A kitchen scale: Baking by weight is far more accurate than volume measurements. Get one that measures in grams.
- A clean glass jar: Something with straight sides so you can track the rise. A 1-quart mason jar works perfectly.
- Flour: Whole wheat or rye flour to start, then unbleached all-purpose or bread flour for ongoing feedings. The whole grains carry more wild yeast and get things moving faster.
- Non-chlorinated water: Chlorine in tap water can inhibit fermentation. Let tap water sit out overnight, use filtered water, or just use bottled water.
- A rubber band or piece of tape: To mark the rise level on your jar.
- A thermometer: Optional but helpful. Your starter ferments best between 70–80°F (21–27°C).
Building Your Starter: Day by Day
Creating a starter from scratch takes about 5 to 7 days. Some people get there faster, some slower. Don’t stress about the timeline — watch for the signs rather than the calendar.
Day 1: The Beginning
Mix 50 grams of whole wheat or rye flour with 50 grams of room-temperature water in your clean jar. Stir vigorously — you want to incorporate some air. Cover loosely (not airtight) and leave it somewhere warm for 24 hours. Don’t put it in the refrigerator. You want that warmth to encourage microbial activity.
Nothing dramatic will happen today, and that’s fine.
Day 2: Patience
Take a look. You might see a few small bubbles forming. You might see nothing at all. Either way, discard half the mixture (about 50 grams), then feed it with 50 grams of all-purpose flour and 50 grams of water. Stir well, cover, and wait another 24 hours.
The “discard” step confuses a lot of beginners. Why throw away flour? Two reasons: it keeps the acidity from building up too quickly and overwhelming the yeast, and it prevents you from ending up with a five-gallon bucket of starter by the end of the week.
Days 3 and 4: Signs of Life
This is when things usually start getting interesting. You should begin to see more consistent bubbling, and the starter may start to rise and then fall between feedings. It might smell funky — even unpleasant, like cheese or nail polish remover. That’s normal. The bacteria are establishing themselves before the yeast fully kicks in.
Keep discarding and feeding at the same time each day. Consistency matters.
Days 5–7: It’s Alive
By now your starter should be reliably doubling in size within 4 to 8 hours of a feeding and falling back down before the next feeding. It should smell pleasantly sour — like yogurt or apple cider vinegar, maybe with a slight yeasty note. The texture will look almost custardy when stirred, full of bubbles throughout.
To confirm it’s ready, try the float test: drop a small spoonful into a glass of water. If it floats, your starter is well-aerated and ready to leaven bread. If it sinks, give it a couple more days.
How to Feed and Maintain Your Starter
Once your sourdough starter is established, you have two options for maintaining it: on the counter or in the refrigerator.
Counter Storage (Daily Bakers)
If you bake every day or every other day, keep your starter at room temperature and feed it once or twice daily. A typical feeding ratio is 1:1:1 — one part starter, one part flour, one part water by weight. So if you keep 50 grams of starter, feed it with 50 grams of flour and 50 grams of water.
Refrigerator Storage (Weekly Bakers)
Most home bakers don’t bake every day. Keep your starter in the fridge and feed it once a week. Pull it out the night before you plan to bake, feed it, let it peak at room temperature, and it’s ready to go. This slows fermentation dramatically and means you can go on vacation without worrying about your starter dying.
A neglected starter that looks sad and has a grayish liquid on top (called “hooch”) isn’t dead — it’s just hungry. Pour off the hooch, discard most of the starter, and feed it back to health over a couple of feedings.
Understanding Autolyse
Once you’re ready to bake your first loaf, you’ll come across the term autolyse. This is a technique where you mix your flour and water together and let them rest — without any starter or salt — for 20 to 60 minutes before continuing.
During autolyse, the flour fully hydrates and gluten begins to develop on its own. This makes the dough more extensible and easier to work with, reduces overall kneading time, and often results in better oven spring and a more open crumb. It’s a small step that pays off in a noticeably improved final loaf.
To do it: mix your flour and water until no dry flour remains, cover the bowl, and walk away. When you come back, the dough will feel smoother and more cohesive. Then add your starter and salt and continue with the recipe.
Bulk Fermentation: The Heart of the Process
Bulk fermentation is the first and most important rise in sourdough baking. After you’ve mixed your dough with your active starter, the entire batch ferments together as one mass — hence “bulk.” This is where flavor develops, where the gluten network strengthens, and where the dough transforms from a shaggy mixture into something with real structure.
Bulk fermentation typically takes 4 to 12 hours, depending on the temperature of your kitchen and the strength of your starter. Warmer environments speed things up; cooler ones slow them down. A good rule of thumb: your dough is ready when it has grown 50 to 75 percent in volume and feels airy and slightly domed on top, with visible bubbles on the surface and sides of the container.
Stretch and Fold
During the first 2 hours of bulk fermentation, you’ll perform a series of stretch and folds to build strength without deflating the dough. Every 30 minutes, wet your hand, grab one side of the dough, stretch it up as high as it will go without tearing, and fold it over to the opposite side. Rotate the bowl 90 degrees and repeat four times to complete one set. Do this 4 to 6 times total.
After these sets, leave the dough alone to finish fermenting. Resist the urge to poke it every 20 minutes.
Shaping, Proofing, and Bread Scoring
Shaping Your Loaf
When bulk fermentation is complete, turn your dough out onto an unfloured surface. The slight stickiness is your friend here — it creates tension. Gently flatten the dough, fold the sides in, then roll it toward you to create surface tension. A well-shaped loaf holds its form and has a tight, smooth exterior.
Place your shaped loaf seam-side up into a well-floured proofing basket (banneton) or a bowl lined with a floured kitchen towel. Cover and refrigerate overnight — typically 8 to 16 hours. This cold proof slows fermentation further, develops flavor, and makes the dough much easier to score.
Bread Scoring
Bread scoring is the practice of making deliberate cuts in the surface of your loaf just before it goes into the oven. These cuts look decorative, but they serve a critical purpose: they control where the loaf expands during baking. Without scoring, the bread will burst unpredictably at its weakest points. With a good score, the loaf opens beautifully along your cut, producing that signature “ear” — the crispy flap that every sourdough baker wants.
Use a bread lame (a razor blade on a stick), a very sharp serrated knife, or a single-edge razor blade. Work quickly and confidently. A timid, slow cut drags the dough instead of slicing through it. For a basic loaf, one straight slash at a 30 to 45-degree angle is all you need. As you get comfortable, you can experiment with decorative patterns.
Score your loaf straight from the refrigerator — the cold dough holds its shape and the blade glides more cleanly through it.