To make a sourdough starter from scratch, mix equal weights of whole grain flour and water, leave it somewhere warm, and feed it daily, discarding most of it each time, then twice a day from day 3. In about a week it should reliably double within 6 to 8 hours of a feeding. At that point it can raise bread.
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That is the method used by King Arthur Baking, and the schedule below follows it. You need no commercial yeast, no grapes, no special water. As Colorado State University Extension puts it, wild yeast is naturally on the flour and in the air. Your job is to give it food, warmth and time.
What you need
- Flour. Whole wheat, rye or pumpernickel for day 1; unbleached all-purpose for the feedings after that.
- Water. Room temperature. King Arthur says tap water is fine unless it is heavily treated.
- A glass jar of at least 1 quart (about 1 litre), with a loose lid or a cloth.
- A kitchen scale. Weighing is far more accurate than cups.
- A rubber band or piece of tape to mark the level after each feeding, so you can see the rise.
- A warm spot. King Arthur recommends a warm room temperature of about 70°F (21°C); below 68°F (20°C) everything slows down.
Which flour should you use?
Start with whole grain. King Arthur recommends whole wheat or pumpernickel (whole rye) flour for the first mix because whole grains carry more of the wild yeast and bacteria you are trying to grow, along with more nutrients for them.
Feed with all-purpose. From day 2 the schedule switches to unbleached all-purpose flour, which makes a starter that is milder and easier to read. You can keep feeding with whole wheat or rye if you prefer; it will usually be more active and more sour, and it will look denser.
Avoid bleached flour. Unbleached flour is the norm for sourdough.
Day-by-day schedule
This is King Arthur Baking’s schedule, by weight.
Day 1. In your jar, mix 50 g whole wheat or pumpernickel flour with 50 g room-temperature water until there is no dry flour. Cover loosely and leave at a warm room temperature for 24 hours. You may see nothing at all.
Day 2. Remove and discard all but 50 g of the mixture. Add 50 g all-purpose flour and 50 g water, stir well, cover and leave for 24 hours. You may see some bubbles or growth, or none.
Day 3. Start feeding twice a day, about 12 hours apart. Each time: keep 50 g of starter, discard the rest, and add 50 g all-purpose flour and 50 g water. King Arthur says you will likely see some activity by now: bubbles, a fresh fruity aroma and some expansion.
Days 4 and 5. Keep feeding twice a day, morning and evening, the same way.
Ready? By the end of day 5, a healthy starter should at least double in volume within about 6 to 8 hours of feeding, with bubbles all the way through and a tangy smell that is pleasantly acidic but not overpowering.
Days 6 and beyond. If it is not there yet, simply keep going with twice-daily feedings until it doubles consistently. That is common, especially in a cool kitchen.
Tip: Don’t pour discard down the drain. In the early days it is too young to bake with in large amounts, but once your starter is a week or two old, discard is a useful ingredient. See our sourdough discard recipes.
What’s normal in the first week?
New starters do strange things. Most of them are fine.
The day 2 to 4 “false rise”
Many starters bubble up dramatically early on, sometimes to several times their volume, then go flat and quiet for a few days. It is easy to think you have killed it. You haven’t.
Baker Debra Wink, writing on The Fresh Loaf, looked at this under a microscope and found that the early activity in her starters came from Leuconostoc bacteria, not yeast. These bacteria produce lots of carbon dioxide while the mix is fairly neutral, then die back as the starter becomes more acidic. The lull that follows is the gap before the acid-loving yeast and lactic acid bacteria you actually want take over. Keep feeding on schedule and the starter usually comes back, and this time for good.
If your starter stays quiet for several days, Wink’s solution was to use unsweetened pineapple juice instead of water for the first couple of days. The acidity holds back the early bacteria and lets the yeast get a foothold.
Liquid on top (“hooch”)
A layer of grey or dark liquid on top is called hooch. King Arthur explains that it is alcohol and water produced by the yeast, and it is a sign the starter is hungry. Stir it back in, or pour it off if there is a lot (more than about half an inch), then feed.
Odd smells
A young starter can smell like many things: yeasty, cheesy, sour, sharp, even a bit like nail polish remover when it is hungry. Smells change as the culture settles down. By the time it is ready, it should smell pleasantly tangy and a bit fruity. An off smell on its own is not a reason to throw a starter away; mould is.
Slow progress
A starter that is slow but bubbling is usually just cold. Move it somewhere warmer, and consider swapping some of the all-purpose flour for whole wheat or rye.
When should you throw a starter out?
Colorado State University Extension is clear: a starter that shows any sign of mould, meaning anything coloured or fuzzy, should not be used. King Arthur adds that streaks of pink or orange mean the culture is likely contaminated and should be tossed.
What is not a problem: a whitish film on a refrigerated starter, which CSU Extension describes as harmless yeast rather than mould, and grey, brown or dark liquid on top.
Safety: If you see fuzzy mould, or pink, orange or other coloured streaks, throw the whole starter away, wash the jar thoroughly and start again. Do not try to scrape it off.
How do you know your starter is ready to bake with?
Use these signs together:
- It at least doubles within roughly 6 to 8 hours of a feeding, and does so day after day.
- It is bubbly all the way through, not just on the surface.
- It has a domed top at its peak that later starts to fall.
- It smells pleasantly tangy, not harsh.
What about the float test?
The float test (drop a spoonful in water and see if it floats) is popular, but King Arthur Baking does not recommend relying on it. A starter that is still rising can float before it is truly ready, and starters made with whole wheat or rye often sink even when they are at their best, because the bran weighs them down. A runny, high-hydration starter can also disperse instead of floating. If it sinks, it is probably not ready; if it floats, check the other signs too.
What next?
Once your starter is reliably doubling, it is time to learn how to feed a sourdough starter on a schedule that suits you, on the counter or in the fridge. Then head to our sourdough for beginners guide and bake your first loaf.
Questions people ask
How long does it take to make a sourdough starter from scratch?
Usually about a week. King Arthur Baking's schedule has a starter doubling within 6 to 8 hours by the end of day 5, but a cool kitchen can add several days.
What flour is best for a sourdough starter?
Whole wheat, rye or pumpernickel flour is the easiest to start with, because whole grains carry more of the natural yeast and bacteria. You can switch to all-purpose flour for regular feedings once it is going.
Why did my starter rise on day 2 and then stop?
That early rise is usually caused by gas-producing bacteria that thrive before the mixture turns acidic. As acidity builds they die back and the starter goes quiet until yeast and lactic acid bacteria take over. Keep feeding.
Do I have to throw away part of the starter?
Yes. Removing some starter before each feeding keeps the volume manageable and gives the remaining culture enough fresh flour. The portion you remove is discard, which you can bake with.
Can I use tap water for a sourdough starter?
Usually yes. King Arthur Baking says tap water is fine unless it is heavily treated; if your starter struggles, try filtered or bottled water.
Sources
- King Arthur Baking — Sourdough Starter
- King Arthur Baking — The float test for yeast dough and sourdough starter
- King Arthur Baking — What to do with the liquid on top of your sourdough starter
- Debra Wink, The Fresh Loaf — The Pineapple Juice Solution, Part 1
- Colorado State University Extension — Sourdough Starter Best Practices
- King Arthur Baking — Sourdough discard: what it is and how to use it