How to Make a Sourdough Starter From Scratch: A Day-by-Day Guide
You need flour, water, a jar, and about two weeks of patience. That is the entire ingredient list for a sourdough starter, and everything else you have read about pineapple juice, grapes, or a friend’s heirloom culture is optional at best.
What you are actually doing is farming. The wild yeast and lactic acid bacteria you want are already present on the flour and in your kitchen. You are not adding them, you are creating conditions where they outcompete everything else, and then keeping those conditions steady until they take over. Understanding that one idea is what gets people through the days where nothing appears to be happening.
What you need
- Flour. Start with whole wheat or rye, which carry far more wild microbes, enzymes, and minerals on the bran than refined white flour does. You can transition to white later. Rye is the most reliable starting flour there is.
- Water. Filtered or bottled, or tap water if your utility does not heavily treat it. A carbon filter removes both chlorine and chloramine, and this matters because chloramine does not off-gas when you leave water out overnight, so the old counter trick fails on most modern municipal supplies.
- A jar. Clear, straight-sided, roughly a litre, loosely covered so gas escapes. Straight sides matter, because a jar that flares makes a rise impossible to read honestly.
- A warm spot. Around 24 to 27°C (75 to 80°F). An oven with only the interior light on works. This is the single biggest variable in how fast you succeed.
A digital scale is not strictly required, but starters built by weight succeed far more often than starters built by cup, because volume measurement of flour is unreliable enough to change your ratios without you knowing.
The day-by-day process
Day 1: mix
Combine 50 g whole wheat or rye flour with 50 g water. Stir until no dry flour remains. Cover loosely and leave it in your warm spot for 24 hours. Nothing visible should happen, and that is correct.
Days 2 to 3: the false rise
You may see vigorous bubbling and a real rise. Almost everyone celebrates here, and almost everyone is celebrating the wrong microbes.
This early activity is usually not your sourdough yeast. It is gas-producing bacteria such as Leuconostoc, which bloom quickly in the fresh, near-neutral environment, produce carbon dioxide, and often smell distinctly unpleasant, sometimes cheesy or like wet hay. They also acidify the jar, which is genuinely useful, because that acidity is what will eventually let the organisms you actually want take hold.
Begin feeding once a day. Discard all but 50 g, then add 50 g flour and 50 g water. The discarding is not waste for its own sake. Without it, acid and spent material accumulate and the culture stalls.
Days 4 to 7: the quiet phase
The bubbling stops. The jar goes flat and stays flat. It may smell sharp or sour. This is the stage where most starters get poured down the sink, and it is the stage where your starter is doing its most important work.
The early bacteria have crashed in the acidic environment they created. The acid-tolerant wild yeast and lactic acid bacteria that define a real sourdough culture are now slowly establishing dominance. They are far slower to build a population, and while they do it there is very little gas and very little to see.
Keep feeding once a day at the same ratio, keep it warm, and do not panic. The lull is the culture reorganizing itself.
Days 7 to 14: it wakes up
Activity returns, and this time it is different. You will see a genuine, repeatable rise that comes a predictable number of hours after each feed. The smell changes from sharp or unpleasant to something recognisably pleasant: yeasty, tangy, faintly like beer or yoghurt.
Once you see activity, move to feeding twice a day, roughly every 12 hours, and consider raising the feeding ratio to 1:5:5 (10 g starter, 50 g flour, 50 g water). More fresh food per feeding gives a longer, cleaner climb to peak and makes the rhythm far easier to read.
How to know it is actually ready
The honest test has nothing to do with floating a spoonful in water. Your starter is ready to bake with when it does all of this consistently:
- It at least doubles in volume after a feed.
- It gets there in a predictable window, usually 4 to 8 hours at room temperature.
- It does the same thing again after the next feed, and the one after that.
- It smells pleasantly tangy rather than sharp, acetone-like, or foul.
Consistency is the whole test. A starter that doubles once and then sulks for three days is not ready. A starter that reliably peaks in six hours every single time is ready, even if it never doubles quite as dramatically as the ones in videos.
The float test, dropping a spoonful into water to see if it floats, is a rough gas check and nothing more. Stiff starters can fail it while being perfectly healthy, and wet ones can sink while fully active. Watch the height and the timing instead. Marking the jar with a rubber band at feeding level turns a vague impression into an actual measurement, and tracking those rise times across feeds is exactly what The Sourdough Companion is built to do for you.
When it goes wrong
Almost every problem in the first two weeks is one of four things, and all four are fixable.
| What you see | What it means | What to do |
|---|---|---|
| Nothing at all after 10+ days | Almost always too cold | Move to 24–27°C and keep feeding |
| Rose on day 3, then died | Completely normal, this is the false rise | Keep feeding, wait out the quiet phase |
| Thin grey liquid on top | Hooch, meaning it is hungry | Stir it in or pour it off, then feed more often |
| Weak, sluggish, never really builds | Refined or stale flour | Switch to fresh whole wheat or rye |
Two things genuinely mean start over: fuzzy mold of any color, and pink, orange, or red streaks. Both mean discard the whole jar without trying to rescue it. Everything else, including smells you find alarming, is nearly always a healthy culture in an awkward phase. For the full diagnostic tree, see why isn’t my sourdough starter rising.
Keeping it alive afterwards
Once your starter is established, maintenance is much lighter than creation.
Baking often? Keep it at room temperature and feed once or twice a day at 1:5:5.
Baking weekly or less? Keep it in the fridge and feed it once a week. Before you bake, take it out and give it one or two feeds at room temperature to wake it up fully. A fridge starter is dormant, not dead, and it will be sluggish on its first feed after a long cold stretch. That is expected.
You can also switch it to white flour at this point if you prefer, though many bakers keep a portion of whole grain in every feed precisely because it keeps the culture more vigorous.
The one thing to remember
Making a starter is mostly a test of whether you can leave something alone while it looks like it is failing. The false rise fools you into thinking you have succeeded early, and the quiet phase fools you into thinking you have failed. Both are just the succession of microbial communities doing exactly what they are supposed to do.
Feed it on schedule, keep it warm, and give it two weeks before you pass judgment. Then build a levain off it for your first bake, and you have a culture that can outlive the oven you bake in.