The float test for yeast dough and sourdough starter: Does it really work?

How do you know when your yeast dough has fully risen? And what about sourdough starter? You feed it and it grows and bubbles for hours, but when is it actually at its baking peak? Many claim dropping a bit of dough or starter into water to see if it floats answers both these questions. But we weren’t convinced — so we did our own float test to find out.

How does the float test work?

Here’s the deal. As the yeast in dough or starter works, it produces tiny bubbles of carbon dioxide. This CO₂, trapped within the glutenous web formed by flour and liquid, makes dough or starter (or an overnight preferment) rise, lightening its consistency in the process.

The float test: fact or fiction? Find out if floating yeast dough in water is truly a good way to judge whether it's fully risen. Click To Tweet

Float test for yeast dough sourdough starter via @kingarthurflour

Let’s do the float test

Yeast dough that’s just begun to rise sinks like the proverbial stone when dropped into water. Float test for yeast dough sourdough starter via @kingarthurflour

But the longer it rises, the more gas is trapped until eventually the dough becomes lighter than water and floats.

So far so good. Yes, fully risen dough will float when placed in water.

Float test fail: false positives

But this test doesn’t go far enough. What about dough that’s not at its peak? Will it remain submerged in water, or pop to the top?Float test for yeast dough sourdough starter via @kingarthurflour

POP!

This is called a false positive: the test result points one way, but the reality is actually something quite different.

I’m using my favorite pain de mie dough for these tests. The recipe calls for the dough to rise for 60 to 90 minutes, until it’s nice and puffy.

The dough above has risen for 30 minutes and is just beginning to climb the sides of the measuring cup. Clearly, it isn’t anywhere near “nice and puffy.” Yet when I place a small scoopful in water, it rises right to the top and stays there.

Float test for yeast dough sourdough starter via @kingarthurflour

What about sourdough starter?

After being refrigerated without feeding for several weeks, my sourdough starter is clearly in need of attention. So I feed it and drop a bit in some water. As expected, it sinks.Float test for yeast dough sourdough starter via @kingarthurflour

Here’s the starter 4 hours later. Note how the bowl of fed starter shows only a few small bubbles; I’d estimate it has at least 2 to 4 hours to go before it’ll be suitable for baking. Yet the starter dropped into water rises right to the top.

So is the float test a good way to assess the rise of yeast dough or baking readiness of sourdough starter?

No.

Both partially risen yeast dough and growing (but not yet ripe) starter will float in water.

Your takeaway

If rising yeast dough or fed sourdough starter sinks in water, it’s definitely not ready to continue to the next step in your recipe.

But just because either floats doesn’t necessarily mean they’re good to go.

Best way to tell if your dough is fully risen? Poke it with your index finger. If the indentation remains, it’s ready to go. If the dough rebounds and your finger mark disappears, it needs more time.

What are the signs of a perfectly ripe starter? It’s very bubbly, and is reliably doubling in size within 6 to 8 hours of feeding.

Want to learn more about rising yeast dough? Read our blog post, The bread also rises. For more information about starter, see our sourdough baking guide.

PJ Hamel
About

PJ Hamel grew up in New England, graduated from Brown University, and was a Maine journalist before joining King Arthur Flour in 1990. PJ bakes and writes from her home on Cape Cod, where she enjoys beach-walking, her husband, two dogs, and really good food!

comments

  1. Mick Emery

    My starter is all bubbly & nice looking, but when I stick my finger in it is very much liquid (y). Not enough flour?

    Reply
    1. The Baker's Hotline

      Mick, your starter should definitely be liquid feeling, so you’re doing it exactly right! The poke test is intended only for dough (whether made with starter or commercial yeast) and not the starter itself. Happy baking! Kat@KAF

  2. Miranda

    And I have found that a too-small piece of starter will always sink. I assume the act of pinching off just a tiny bit pushes all the gas out. I now go for approximately 2 tablespoons of starter – a good clump, enough that I’ve grabbed, and not squished, some bubbles.

    Reply
  3. Mini H

    I have a new starter that I have been working with for several weeks. I’ve followed the directions that came with the Alaskan starter, but it doesn’t seem to rise very much, and I have thrown away several loaves of bread that look great, but are heavy and hard as a stone.. The starter is very thin. Any suggestions?

    Reply
    1. The Baker's Hotline

      Hi Mini! It sounds like there is a little too much liquid being used to feed your starter. Sourdough starter should be the consistency of thick pancake batter, so we’d recommend holding back some water next time you feed your starter. You may also want to check out our Mainting your sourdough starter blog article, for our recommended feeding amounts for a starter. Your starter will strengthen over time and become better at providing a stronger rise for your bread, so we’d encourage you to give it a little more time to develop. Happy baking! Morgan@KAF

  4. S. Rose

    Basically, this is a test for density with, unfortunately, one single bit of resolution. You can get much more precision just by measuring the density directly – for example, take the weight of a tablespoon of your starter or dough. If it’s 14g, that’s precisely the density of water. Anything above that weight would sink and anything below would float, but by making the measurement you can see just how much above or below. The precision is limited by how accurately you can get a fixed volume of product (and the resolution of your scale).

    Reply
  5. Susannah

    I have definitely experienced this with preferments and starter. I started using clear glass containers for them so I could see the formation of gas bubbles inside the dough, and that helped me a lot when learning what to look for. I am able to do it by sight now, but it was quite a bit of experimenting to learn what to see, smell, feel, et cetera.

    Reply
  6. Karen

    I do this with tamale dough. Beat the heck out of lard and masa w/ baking powder till it floats in cold h2o. Seems to make cornmeal casing less dense ie heavy.

    Reply
    1. PJ Hamel, post author

      Karen, I hadn’t thought about floating baking powder doughs — interesting! Thanks for sharing your experience here — PJH@KAF

  7. Grace

    I’m confused by the float test. My very bubbly starter, that never doubled after being fed but would maybe grow a little more than 50% before starting to fall, in about 3 hours, would float initially but then after a minute, it sinks. So my question is, how long does the floater have to stay floating for it to be ready for rising bread?

    Reply
    1. PJ Hamel, post author

      Grace, I honestly don’t think you can say that a floating starter, no matter how long it floats, is proof that it’s fully ripe. My tests show that a starter that isn’t ripe will float; and will remain floating until it gradually absorbs the water in which it’s floating and disintegrates and sinks. So I wouldn’t trust the float test — except to note that a starter that immediately sinks and stays on the bottom isn’t ready to use. Hope that makes sense! PJH@KAF

  8. Xochitl Gonzalez

    My brioche recipe tells my to test my poolish by doing the float test and of all the times I’ve made the bread, successfully, it has only ever floated once. I don’t bother trying any more.

    Reply
    1. PJ Hamel, post author

      By this time you probably can recognize by sight when the dough has risen enough — I always say, do whatever works for YOU, never mind what anyone else says! Thanks for adding your feedback here, Xochitl — PJH@KAF

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