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Make a sourdough starter
Level 1 · beginner
Flour, water and patience. You feed it every day until it doubles within 4 to 6 hours, and from day 7 it can raise a loaf.
- Time
- 7–14days
- Temperature
- 70–82°F
- Jar
- 1L
The golden rule: raw flour and dough aren't for tasting; throw the starter out if mold appears.
No sign-up. We guide you step by step, from the scale to the fridge.
Reviewed October 26, 2026 · 53 facts, each with its source
You'll need
- 1-liter wide-mouth glass jar (about a quart), with a lid
- A rubber band, to mark the level
- Spatula or spoon, not copper or iron
- Kitchen scale that weighs in 1 g steps
- Room thermometer (optional)
Step by step
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Day 1: mix the rye with the water and mark the level
Clean the counter, the jar and the spatula, and wash your hands. Weigh the empty jar and write the weight down: it tells you how much is left inside when you discard some later. Put 50 g of whole rye flour and 55 g of water in the jar and stir until no dry flour is left. Put a rubber band around the jar, right at the level of the mixture, to see how much it rises.
Put the lid on without screwing it down: the starter gives off gas and needs no air. Leave it for 24 hours somewhere warm, at 70–82 °F.
Tip: Tap water usually carries chlorine or chloramine, which can kill the good bacteria. Use filtered or spring water, or let a pitcher of tap water stand overnight. If your water has chloramine, use filtered or spring water.
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Days 2 and 3: feed it once a day
Stir the starter and discard most of it, leaving just 50 g in the jar. With the empty jar's weight that's easy: the jar plus 50 g. Add 25 g of bread or all-purpose flour, 25 g of whole rye and 50 to 55 g of water, and stir until no dry flour is left. Move the rubber band to the new level, cover loosely and leave it for another 24 hours at 70–82 °F.
From day 2, half rye and half white flour works best: it gives the microbes food they can use more easily. Each feeding has at least as much flour and as much water as starter, by weight. You discard some for two reasons: it would pile up, and it would get too sour.
Tip: It's normal for little to change on day 1. In the first days the microbes that come with the flour lead and it smells of toasted grain; little by little the acid-making bacteria take over. That's why what you discard in the first week goes in the trash or the compost, not into cooking (our house rule).
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From day 4: two feedings a day, 12 hours apart
Carry on the same way, but twice a day, 12 hours apart: keep 50 g, add 25 g of bread flour, 25 g of rye and 50 to 55 g of water, stir, move the band and cover loosely. A starter takes 14 days to a month to get established.
Tip: If it's sluggish and won't rise, move it somewhere warmer or use more rye. The closer to 82 °F, the more active it is; too warm, and it rises and falls so fast it runs out of food.
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Check whether it's ready
It's ready when all of this is true:
- It rises and falls on schedule, and doubles within 4 to 6 hours of a feeding.
- It's mousse-like: stretchy and airy, pourable but not watery.
- It smells yeasty and pleasant.
- It has bubbles on top and some large ones on the sides.
It can raise bread from day 7, but it bakes better from day 14 on: the good bacteria take time to take over. In a study of ten flours, the pH settled at 3.6, and every starter was mature, stable and ready to bake by day 10.
Tip: Don't taste it to tell if it's ready: it's raw flour. Go by the bubbles, the sour smell, the texture, how much it rises and the notes you've kept.
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Use it at its peak and keep feeding it
To make bread, use it at its peak: when it has doubled, about 4 to 6 hours after a feeding and before it falls back. If you bake every day or 3 or 4 times a week, keep it on the counter and feed it once a day. If you bake less often, keep it covered in the fridge and feed it once a week. The recipe "Keep your starter going" explains how.
Tip: Once it's ready and active, you can feed it all-purpose flour alone.
No sign-up. We guide you step by step, from the scale to the fridge.
Variations
The same method, a different flavor. Once you have this one down, try one of these.
What you'll see
A sourdough starter is flour and water fermented by the wild yeasts and lactic acid bacteria that already live on the flour and in the air. You don't need commercial yeast. As it ferments it turns sour, and that acidity helps hold back the microbes we don't want. You feed it every day, for one or two weeks, until it doubles after each feeding. This is the University of Illinois method: it starts with whole rye and goes on with half rye and half wheat.
Whole rye flour is the dark, whole-grain kind. Bread flour is the white wheat flour for bread; all-purpose flour works too.
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How to tell it's going well
- Don't taste it, or any raw dough. Flour is a raw food: it hasn't been treated to kill germs such as E. coli or Salmonella, and they die only when it's baked or cooked. Wash your hands with soap and water after handling it.
- Fuzz or colored spots mean mold. Throw the whole starter out, clean the jar well and start again. Don't sniff it.
- Pink or orange streaks: throw it out too. In Alaska, where sourdough is a tradition, discolored starters aren't used today.
- A dark liquid on top that smells of alcohol is normal. It's called hooch: pour it off or stir it in, as you like.
- Keep the lid loose. The starter gives off gas.
- Glass, food-grade plastic or stainless steel. Never copper, iron or galvanized metal.
- Only flour and water. Starters made with milk and sugar, like Amish friendship bread, have been linked to rare cases of foodborne illness.
Where every number comes from
Every number in this recipe comes from a food safety guide. We keep a copy of each source and quote its exact words.
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1
Wild yeast is already on the flour and in the air
“Wild yeast is naturally on the flour and in the air.”
Colorado State University Extension (Farm to Table) · Sourdough Starter Best Practices (March 2020) · read on October 25, 2026
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2
No commercial yeast needed
“nor does commercial yeast need to be added when making a sourdough starter.”
Colorado State University Extension (Farm to Table) · Sourdough Starter Best Practices (March 2020) · read on October 25, 2026
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3
Fermentation acidifies it, which helps hold back pathogens
“The fermentation process will acidify the starter, which helps prevent pathogen growth.”
Colorado State University Extension (Farm to Table) · Sourdough Starter Best Practices (March 2020) · read on October 25, 2026
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4
A loose lid lets the gas out; it needs no air
“The starter should be loosely covered in order to safely release the gas, but the culture does not require oxygen.”
Colorado State University Extension (Farm to Table) · Sourdough Starter Best Practices (March 2020) · read on October 25, 2026
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5
Judge it by bubbles, smell, texture and rise, not by tasting
“Instead, a bubbly appearance, tangy smell, batter-like consistency, expansion, and records of preparation steps should be used to determine when your starter is ready.”
Colorado State University Extension (Farm to Table) · Sourdough Starter Best Practices (March 2020) · read on October 25, 2026
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6
Don't taste raw starter
“Do not taste raw sourdough starter before baking.”
Colorado State University Extension (Farm to Table) · Sourdough Starter Best Practices (March 2020) · read on October 25, 2026
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7
With mold, throw it out and clean the jar well
“Sourdough starter that shows any sign of mold (colored and/or fuzzy) should NOT be used, and the container should be thoroughly cleaned and rinsed before starting over.”
Colorado State University Extension (Farm to Table) · Sourdough Starter Best Practices (March 2020) · read on October 25, 2026
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8
A liquid layer that smells of alcohol is fine
“Sourdough starter may develop a liquid layer that smells of alcohol, and this is fine.”
Colorado State University Extension (Farm to Table) · Sourdough Starter Best Practices (March 2020) · read on October 25, 2026
Show the remaining 45 claims
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9
Starters with milk and sugar have been linked to rare illness
“Although rare, there have been incidents of foodborne illness associated with friendship-style bread, which differs from traditional sourdough by addition of milk and sugar”
Colorado State University Extension (Farm to Table) · Sourdough Starter Best Practices (March 2020) · read on October 25, 2026
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10
Counters and equipment washed and sanitized
“Wash and sanitize countertops and equipment.”
University of Illinois Extension · Sourdough Bread: 101 (modified December 2025) · read on October 25, 2026
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11
At least equal weights of starter, flour and water
“Feed a minimum 1:1:1 ratio, equal parts by weight of starter, flour, and water.”
University of Illinois Extension · Sourdough Bread: 101 (modified December 2025) · read on October 25, 2026
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12
It takes 14 days to a month to establish
“It can take 14 days to a month to establish a starter. It must be fed daily and twice daily starting on day 4.”
University of Illinois Extension · Sourdough Bread: 101 (modified December 2025) · read on October 25, 2026
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13
If it's sluggish, more warmth or rye flour
“If it’s sluggish and not rising, consider putting it in a warmer environment and/or switching the flour, such as all-purpose or bread flour to rye flour.”
University of Illinois Extension · Sourdough Bread: 101 (modified December 2025) · read on October 25, 2026
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14
Ready when it doubles within 4–6 hours of feeding
“It consistently falls and rises; the starter at least doubles within 4-6 hours after feeding.”
University of Illinois Extension · Sourdough Bread: 101 (modified December 2025) · read on October 25, 2026
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15
Mousse-like, pourable but not watery
“It has a stretchy, aerated, mousse-like consistency that is pourable but not watery.”
University of Illinois Extension · Sourdough Bread: 101 (modified December 2025) · read on October 25, 2026
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16
Smells yeasty and pleasant
“It smells yeasty and pleasant.”
University of Illinois Extension · Sourdough Bread: 101 (modified December 2025) · read on October 25, 2026
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17
Bubbles on top and some large ones on the sides
“It has bubbles on the top and some large bubbles on the sides.”
University of Illinois Extension · Sourdough Bread: 101 (modified December 2025) · read on October 25, 2026
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18
Bakeable from day 7; better from day 14
“It’s been at least 14 days (while a starter can be used to make bread on day 7”
University of Illinois Extension · Sourdough Bread: 101 (modified December 2025) · read on October 25, 2026
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19
Use it at its peak, doubled and before it falls
“it’s best to use it when it has at least doubled in size, usually about 4-6 hours after you’ve fed it, before falling back down.”
University of Illinois Extension · Sourdough Bread: 101 (modified December 2025) · read on October 25, 2026
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20
If you bake often, on the counter and fed daily
“Every day or 3-4 times per week: Feed it daily and leave it on the counter or in a warm place.”
University of Illinois Extension · Sourdough Bread: 101 (modified December 2025) · read on October 25, 2026
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21
If mold appears, throw it out
“Discard the starter if mold appears.”
University of Illinois Extension · Sourdough Bread: 101 (modified December 2025) · read on October 25, 2026
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22
The liquid on top is hooch; pour it off or stir it in
“This liquid is known as “hooch.” Pour it off or stir it in”
University of Illinois Extension · Sourdough Bread: 101 (modified December 2025) · read on October 25, 2026
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23
Non-reactive containers; never copper, iron or galvanized metal
“Non-reactive containers. Include wide-mouth mason jars, plastic containers, glass bowls, or crocks. Do not use copper, iron, or galvanized metal.”
University of Illinois Extension · Sourdough Bread: 101 (modified December 2025) · read on October 25, 2026
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24
Day 1, 50 g whole rye flour and 55 g water
“Add 50 grams (½ cup) of whole rye flour* and 55 grams (¼ cup) of unchlorinated water* to the mason jar”
University of Illinois Extension · Sourdough Bread: 101, Sourdough Starter Recipe and Sourdough Recipes #1-3 (modified December 2025) · read on October 25, 2026
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25
Whole rye works well on day one
“Whole rye or other whole grain flour is great on day one, as wild yeasts love it.”
University of Illinois Extension · Sourdough Bread: 101, Sourdough Starter Recipe and Sourdough Recipes #1-3 (modified December 2025) · read on October 25, 2026
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26
Weigh the empty jar and write it down
“weigh an empty wide-mouth mason jar and write the weight in grams.”
University of Illinois Extension · Sourdough Bread: 101, Sourdough Starter Recipe and Sourdough Recipes #1-3 (modified December 2025) · read on October 25, 2026
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27
A rubber band marks the level
“Place a rubber band around the jar, marking the starter’s top, indicating rise.”
University of Illinois Extension · Sourdough Bread: 101, Sourdough Starter Recipe and Sourdough Recipes #1-3 (modified December 2025) · read on October 25, 2026
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28
Loosely covered, 24 hours at 70–82 °F
“Cover loosely and place somewhere warm (70-82 F is best) for 24 hours.”
University of Illinois Extension · Sourdough Bread: 101, Sourdough Starter Recipe and Sourdough Recipes #1-3 (modified December 2025) · read on October 25, 2026
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29
Chlorine and chloramine in tap water can kill good bacteria
“Tap water is usually treated with chlorine or chloramine, which can kill good bacteria.”
University of Illinois Extension · Sourdough Bread: 101, Sourdough Starter Recipe and Sourdough Recipes #1-3 (modified December 2025) · read on October 25, 2026
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30
Filter the water or let it stand overnight
“To dechlorinate tap water, use a water filter or fill a pitcher of water and let it stand overnight.”
University of Illinois Extension · Sourdough Bread: 101, Sourdough Starter Recipe and Sourdough Recipes #1-3 (modified December 2025) · read on October 25, 2026
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31
With chloramine, use spring or filtered water
“If water is treated with chloramine, it is best to use spring or filtered water.”
University of Illinois Extension · Sourdough Bread: 101, Sourdough Starter Recipe and Sourdough Recipes #1-3 (modified December 2025) · read on October 25, 2026
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32
Days 2 and 3, one feeding a day
“Begin feeding the starter once per day.”
University of Illinois Extension · Sourdough Bread: 101, Sourdough Starter Recipe and Sourdough Recipes #1-3 (modified December 2025) · read on October 25, 2026
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33
Keep 50 g and discard the rest
“discard enough starter so that 50 grams (¼ cup) remain.”
University of Illinois Extension · Sourdough Bread: 101, Sourdough Starter Recipe and Sourdough Recipes #1-3 (modified December 2025) · read on October 25, 2026
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34
Each feeding, 25 g wheat flour, 25 g rye and 50–55 g water
“Add 25 grams (¼ cup) organic, unbleached bread or all-purpose flour, 25 grams (¼ cup) whole rye flour, and 50-55 grams (¼ cup) unchlorinated water to the starter”
University of Illinois Extension · Sourdough Bread: 101, Sourdough Starter Recipe and Sourdough Recipes #1-3 (modified December 2025) · read on October 25, 2026
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35
From day 2, half rye and half white flour
“on day two and beyond, it’s best to use 50% rye or whole wheat flour and 50% organic, unbleached bread or all-purpose flour, as these flours provide more readily available food.”
University of Illinois Extension · Sourdough Bread: 101, Sourdough Starter Recipe and Sourdough Recipes #1-3 (modified December 2025) · read on October 25, 2026
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36
From day 4, two feedings a day, 12 hours apart
“Begin two feedings per day, 12 hours apart”
University of Illinois Extension · Sourdough Bread: 101, Sourdough Starter Recipe and Sourdough Recipes #1-3 (modified December 2025) · read on October 25, 2026
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37
Lid on, screw band loose
“Cover the jar loosely. Just the lid; don’t tighten the screw band.”
University of Illinois Extension · Sourdough Bread: From Starter to Loaf Webinars FAQs (modified December 2024) · read on October 25, 2026
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38
You discard some because it grows too big and too sour
“Both! You'll have too much quantity built, but also it can become too acidic.”
University of Illinois Extension · Sourdough Bread: From Starter to Loaf Webinars FAQs (modified December 2024) · read on October 25, 2026
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39
The closer to 82 °F, the more active
“you generally want to keep it in the range of 70-82°F, but the higher range, the more active your starter will be.”
University of Illinois Extension · Sourdough Bread: From Starter to Loaf Webinars FAQs (modified December 2024) · read on October 25, 2026
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40
Too warm and it rises and falls too fast
“Too high, though, and it will consume the sugars/starches too fast causing it to peak and fall too quickly.”
University of Illinois Extension · Sourdough Bread: From Starter to Loaf Webinars FAQs (modified December 2024) · read on October 25, 2026
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41
Once active, it can live on all-purpose flour
“when your starter is ready and active, you can make it all 100% all-purpose.”
University of Illinois Extension · Sourdough Bread: From Starter to Loaf Webinars FAQs (modified December 2024) · read on October 25, 2026
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42
Stainless steel is non-reactive
“Yes, stainless steel is non-reactive.”
University of Illinois Extension · Sourdough Bread: From Starter to Loaf Webinars FAQs (modified December 2024) · read on October 25, 2026
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43
Little changes on day 1
“On day 1, starters showed little to no change in either pH or height compared to day 0.”
PeerJ, McKenney et al. · Sourdough starters exhibit similar succession patterns but develop flour-specific climax communities (2023) · read on October 25, 2026
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44
Early on, flour microbes lead and it smells of toasted grain
“Day 1 starter cultures were dominated by microorganisms commonly associated with plants and flour, and by aromas similar to toasted grain/cereal.”
PeerJ, McKenney et al. · Sourdough starters exhibit similar succession patterns but develop flour-specific climax communities (2023) · read on October 25, 2026
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45
In one study, mature and stable by day 10
“Our results confirm that sourdough starters are functionally mature and stable (i.e., suitable for baking) by day 10 across flour types”
PeerJ, McKenney et al. · Sourdough starters exhibit similar succession patterns but develop flour-specific climax communities (2023) · read on October 25, 2026
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46
Acid-making bacteria rule a mature starter
“Acid producing and acid-tolerant taxa dominate mature starters across all flour types.”
PeerJ, McKenney et al. · Sourdough starters exhibit similar succession patterns but develop flour-specific climax communities (2023) · read on October 25, 2026
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47
The pH settled at 3.6
“after which starters stabilized at a pH of 3.6”
PeerJ, McKenney et al. · Sourdough starters exhibit similar succession patterns but develop flour-specific climax communities (2023) · read on October 25, 2026
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48
If not, covered in the fridge and fed weekly
“Keep your starter covered in an air-tight container and refrigerated when not in use. Ideally, feed and use the starter weekly.”
Colorado State University Extension (FoodSmart Colorado) · Sourdough Basics: Caring for your Starter and Making Bread (reviewed October 2025) · read on October 25, 2026
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49
Raw flour can carry E. coli and Salmonella
“That means it hasn't been treated to kill germs that cause food poisoning, such as Escherichia coli (E. coli) and Salmonella.”
CDC · Raw Flour and Dough · read on October 25, 2026
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50
Germs are killed only by baking or cooking
“Germs are killed only when flour is baked or cooked.”
CDC · Raw Flour and Dough · read on October 25, 2026
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51
Hands washed with soap and water after handling flour
“Wash your hands with soap and water after handling flour, raw eggs, or any surfaces they have touched.”
CDC · Raw Flour and Dough · read on October 25, 2026
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52
Don't sniff mold
“Don't sniff the moldy item. This can cause respiratory trouble.”
USDA Food Safety and Inspection Service · Molds on Food: Are They Dangerous? · read on October 20, 2026
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53
In Alaska, discolored starters aren't used
“Modern Alaskans do not use discolored starters”
University of Alaska Fairbanks Cooperative Extension Service · Sourdough (FNH-00061, revised October 2024) · read on October 25, 2026
