How to Make Sourdough Starter from Scratch (7-Day Rye Method)

Every class I teach starts with the same confession: students want to know how to make sourdough starter, and they are convinced it requires either a gift from a friend’s century-old crock or some kind of microbial luck. Neither, y’all. A sourdough starter is flour, water, a jar, and seven days of five-minute check-ins. The wild yeast is already on the flour; your only job is to feed it until it wakes up. Here is the exact method I have used to start hundreds of cultures, including the one my bakery still bakes with.

What do you need to make a sourdough starter?

Fifty grams of whole rye flour and fifty grams of water per feed, plus a clean glass jar. That is the entire shopping list. I build every new starter on stone-ground whole rye because its bran carries the densest population of wild yeast and it visibly bubbles in 24 to 48 hours, where a white-flour starter can take 4 to 6 days. Our best flour for sourdough starter guide covers the why in depth; this post is the how.

A kitchen scale matters more than any ingredient here. Volume measures drift, and a new starter is the one bake where consistency beats everything. Mind you, there is no salt, no sugar, no commercial yeast, and no fruit juice in this method. Flour and water are genuinely all it takes.

How do you make a sourdough starter from scratch?

Mix equal weights of rye flour and water on day one, then once a day discard half the jar and feed what remains with fresh flour and water until it reliably doubles within 6 to 8 hours, which takes 5 to 7 days; then switch the feed to all-purpose flour for everyday maintenance. Day by day:

1. Day 1: mix. Stir 50 g whole rye flour and 50 g room-temperature water in the jar until no dry pockets remain. Cover loosely (a resting lid or cloth, never airtight) and leave it at room temperature, ideally 70 to 75°F.
2. Day 2: first feed. You may already see a few bubbles on rye. Discard half the jar, then stir in a fresh 50 g flour and 50 g water. Discarding is not waste; it keeps the acidity and volume in check so the yeast stays fed.
3. Days 3 to 4: hold your nerve. Many starters go strangely quiet here after a lively day 2. That first burst was a bacterial false start; the true yeast population is still building. Keep the daily discard-and-feed rhythm exactly the same.
4. Day 5: real activity. The starter should now rise noticeably between feeds, roughly doubling in 8 to 12 hours, with a tangy, yogurt-like smell and a domed, bubbled surface.
5. Days 6 to 7: the readiness bar. When it doubles within 6 to 8 hours of a feed, predictably, on consecutive days, it is ready to raise bread.
6. Switch to maintenance. Move the feed to unbleached all-purpose flour (or a 75/25 AP-and-whole-grain blend) for a calmer, milder everyday culture, and bake whenever it is at peak.

How do you feed a sourdough starter?

Discard half, then add equal weights of flour and water: that is a feed, and during the build week you do it once a day. A mature starter on the counter graduates to the classic 1:1:1 ratio (equal weights starter, flour, and water; 10 g of each is plenty), fed twice daily, which uses about 140 g of flour a week. If that sounds like a part-time job, keep the starter in the fridge on an all-purpose feed instead and feed it weekly; the cold slows the culture without harming it. Feeding always follows the same logic: yeast ate the last meal, so you remove some of the crowd and set out fresh food.

How do you know when your starter is ready?

The doubling test is the one that matters: a starter that doubles in volume within 6 to 8 hours of a feed, twice in a row, will raise a loaf. Mark the level with a rubber band after feeding and check the clock, not your hopes. The popular float test (a spoonful of starter floats in water when gassy) is a decent spot-check at peak, but it throws false negatives on young rye starters because the batter is heavy, so do not let a sinking spoonful overrule two clean doublings. Your nose is the third gauge: ready starter smells tangy and faintly fruity, not like nail polish or old gym socks.

Why isn’t my sourdough starter bubbling?

Nine times out of ten, nothing is wrong: days 3 and 4 are famously quiet while the yeast population catches up to the bacteria, and the fix is to keep feeding on schedule. The genuine problems announce themselves differently; the table covers them alongside that normal quiet phase:

Only that last row means starting over. Everything else is a starter behaving like the slightly moody culture it is. Patience and a warm corner solve most of it. A few 100% rye feeds are the standard rescue for a genuinely sluggish culture (activity usually doubles within 48 hours), and our rye flour guide covers why rye’s bran-rich flour earns that job.

Do you have to use rye flour?

No, but it is the difference between a 5-to-7-day build and one that can stretch past ten. Any unbleached flour with its bran intact will get there: whole wheat runs a day or two behind rye, plain all-purpose slower still, and heritage wheats like spelt sit somewhere between. The one non-negotiable is avoiding bleached flour, where the chlorine treatment has knocked back the wild microbes you are trying to cultivate. Gluten-free bakers can build a starter on the same schedule with sorghum or brown rice flour; our gluten-free sourdough bread method builds its starter on brown rice at 30 g per feed.

What do you do with all the discard?

Bake with it. The half-jar you remove before each feed is unfermented-bread batter, not garbage, and it is the secret ingredient behind an entire genre of recipes: our sourdough discard recipes collection runs from discard banana bread to English muffins. During the build week the discard is young and mild; from day 4 onward it carries real tang. And while your starter spends its week growing up, dinner still happens; a rice cooker full of perfectly cooked quinoa asks even less of you than the starter does.

Your first loaf

When the doubling test passes, feed the starter, wait for peak, and bake: our whole grain sourdough bread is the natural first loaf, and the Real Bread Campaign’s sourdough guidance is a good independent reference for what real sourdough fermentation involves. The microbiology behind all this, a stable community of wild yeasts and lactic acid bacteria, has its own long story on Wikipedia’s sourdough entry if you like knowing why the jar smells the way it does.

Seven days, one jar, and about half an hour of actual hands-on work spread across the week. The starter you build this week can outlive every appliance in your kitchen. Mine is eight years old and shows no sign of slowing down.