Ripe Sourdough Starter: What does "ready to use" look like?

Sift’s Spring issue goes into sourdough baking in depth, with articles on sourdough breads and the sweet side of sourdough. To complement those recipes, we’d like to share this Techniques column. How do you know when your sourdough starter is ready to bake with? Let’s take a look.
We’ve answered hundreds of questions on this topic, but in this case it seems some pictures could well be worth a few thousand words.
sourdough Starter

Wake up your sourdough starter

Your starter has been tucked safely in the refrigerator for… awhile. Ten days, maybe longer. It’s separated, with a few tiny bubbles in the bottom, and a layer of grayish-looking alcohol on top. This is the sight that generates a lot of phone calls to our hotline. Can this possibly be OK? Is it dead?

Despite its current uninspiring appearance, this starter is still capable of doing great things.

sourdough Starter

Your sourdough starter’s first meal

Stir everything back together (some people just pour off the top layer, which is OK, too), discard half, and feed the remainder with equal weights of flour (a scant 1 cup, 4 ounces) and water (1/2 cup, 4 ounces). Mix well, cover, and leave on the counter for 12 hours. Repeat the discard and feeding process every 12 hours, leaving the starter on the counter. After a few feedings, you’ll see the starter becoming more and more active, doubling in size in a shorter time.

Looking for ideas of what to do with that discarded starter? Visit this page to get a whole collection of recipe ideas.

sweet sourdough baking via@kingarthurflour

Get ready to bake

This is the same starter after a few days of the regular feedings described above. We stirred, discarded, and fed it with flour and water at 8 a.m. (2 hours ago). Now we’re going to watch its development. See the number and size of the bubbles increasing?sourdough starter via@kingarthurflour

Active, but not ripe, sourdough starter

The same starter at 1 p.m., 5 hours after feeding. It’s beginning to expand, and has many more bubbles. If you watch it for a minute, you can see the bubbles forming and coming to the surface in slow motion. This is an active starter, growing and expanding, producing bubbles of carbon dioxide. But it’s not yet ripe (at the top of its yeast and bacteria growth arc), nor at full strength for raising dough.sourdough starter via@kingarthurflour

Ripe and ready to go

The same starter at 4 p.m., 8 hours after feeding. It’s doubled in volume, and shows signs of just beginning to sag under its own weight. This is active starter that’s also ripe, ready to be added to bread dough to perform its sourdough magic. After mixing it into dough, then some rising and folding, the dough can be shaped and refrigerated overnight to be baked tomorrow.

sourdough Starter

The best way to measure sourdough starter

An important thing to note about measuring sourdough starter: The more bubbles in it, the less a cup of active, ripe starter weighs. Measuring by volume can mean you have more or less starter in your cup, depending on where it is on its growth curve. That’s not a deal breaker for your recipe, but having a different amount of starter than called for may change the rising times and finished size of your loaf. To be sure you have the lifting power you need, measuring ripe starter by weight is always a better choice.

Once you gain confidence that your starter is vigorous, you can move its “get ready” feeding to the evening, knowing your starter will be ripe next morning to mix into your dough.

Your sourdough baking adventures await. We have lots of ideas (more than 150 recipes) to help you navigate this tasty and rewarding style of baking. Be sure to visit our sourdough guide for more in-depth information about creating, maintaining, and baking with sourdough.

At Sift, we live and breathe baking, and hope you’ll join us. Baking together is always more fun.

Susan Reid

Chef Susan Reid grew up in New Jersey, graduated from Bates College and the Culinary Institute of America, and is presently the Food Editor of Sift magazine. She does demos, appearances, and answers food (and baking) questions from all quarters.


  1. Margot

    At the end of the article, it says it’s best to measure the starter by weight instead of volume. When King Arthur Flour recipes call for 1 cup sourdough starter, how much should this weigh?

    Thank you!

    1. Susan Reid, post author

      Margot, that depends on what stage the starter is in its development. Unfed starter can weigh as much as 8 3/4 ounces per cup; a cup of ripe, active starter is unlikely to weigh more than 7 1/2. Susan

  2. bj helton

    If I feed on Friday and let it sit out, then refrigerate and want to bake on Sunday, is the starter ready to use as is, or is it considered”unfed”. Some of the KA recipes, like the pretzels, calls for the unfed, the bread calls for “fed”

    1. Susan Reid, post author

      Depends, BJ, on what the starter looks like to begin with. If it looks better than the first photo and not as good as the third, I’d recommend feeding it on Friday night, Saturday morning, and Saturday night before using it to bake with on Sunday. Susan

  3. Caite McKinney

    I was interested to see you can form and “rise” a loaf and then refrigerate it and bake later. How long can you leave the loaf in the fridge? I assume you don’t slash until just before baking. This would solve the dilemma I always face as a working Mom who is never at home at the right times for feeding the starter, “raising” and then baking the loaf!

    1. Susan Reid, post author

      Once a sourdough loaf has had its first rise and then been shaped, you can put it in the fridge overnight and bake it the next day. Take it out and leave at room temperature while the oven heats up; you should still slash the loaf before baking. It will help the bread keep a more uniform shape as it rises. Susan

  4. Lucy

    one more question if I may, when I feed my starter I take equal weights of unfed starter, water, and flour. Is this correct?

  5. Lucy

    I have been just feeding my starter, letting it double, using what I need and refrigerating the rest. Do I really need to discard?

    1. Susan Reid, post author

      Lucy, that depends on what your starter looks like when it comes out of the refrigerator. If it starts out looking more like the second or third jar, you’re in decent shape. It also depends on how sour you like your bread to be. When I use my starter after its been cooling its heels for a while after only 1 feeding, I don’t get as high a rise for my bread and its very, very sour. If you like the results you’re getting, stay where you are. But I would give it at least one feed and a couple of hours on the counter before putting it away, to answer your next question. Susan

  6. Sandra Taylor

    Do you discard half of the starter before feeding it so it doesn’t overflow the jar? I don’t understand why you throw half of it away. You could give it to a friend couldn’t you? I use sourdough starter but mine is fed with potato flakes, sugar and warm water. It never rises like the KAF sourdough does. It does bubble though. I have used it interchangeably with KAF recipes, which are the best by the way.

    1. Susan Reid, post author

      Hi, Sandra. Yes, of course, you can share your discard with a friend. The reason you need to discard half is because as your starter sits, the yeast and bacteria generate both lactic and acetic acid. That acid, in high enough concentrations, inhibits the growth curve that you’re trying to capture. The starter you’re using now is called a Friendship starter, and is usually part of quick bread recipes. Thanks for the props about our recipes! Susan

  7. Carol B.

    Thank you for this article! I just made my sourdough bread last night with starter that looked just like the ‘starved’ photo. Of course I fed it overnight, and it did make decent bread, but now I know it could be a LOT better, and without adding yeast to it, as I did do, just to be safe. Very timely! I have learned a great deal from your website this past year. I have been making good bread for 40 years, but now it comes out better, easier! Thank you! Thank you!! LOVE IT!

    1. Susan Reid, post author

      Hooray, Carol! We were hoping this blog post would turn on just that sort of light bulb. Glad to be of service! Susan

  8. Lisa Meeker

    My husband insists that a metal spoon should not be used when mixing the water and flour in. Is this really a thing? He believes it should be mixed with a wooden spoon. Do I need to worry about this detail? Thank you! (I’m using sourdough starter my Uncle and Cousin have kept alive since the mid-1960’s.)

    1. Susan Reid, post author

      Hi, Lisa. Unless the spoon being used is a) aluminum and b) sits in VERY acidic starter for about 3 days (which would start to corrode the metal and give the starter an off flavor), there’s no reason not to use a metal spoon to stir starter. I use our dough whisk to stir things together when feeding my starter; it’s the perfect tool for the job. And a wooden spoon works just fine, too.

  9. Julie Tucker

    Hi-in the sourdough tips and recipes booklet that comes with KAF sourdough starter, there is a recipe for multigrain sourdough. What can I use in place of the harvest grain blend? Thank you

    1. Susan Reid, post author

      Julie, you can use any combination of grains and seeds you happen to like and have on hand. Simplest is to use an equal volume of rolled oats, but if you have some Wheaties in the house that could go into the mix, too. Flax seeds, sesame or sunflower seeds for some of the volume, as well. Susan

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