Float Test for Starter or Levain? Is there a difference?


Hello, I'm new to baking and trying to get a sourdough starter going.  Mine consists of 40g that I keep each time, then I add 40g water, and 40g King Arthur bread flour each day (I plan to scale the daily feedings back once I get this all figured out.)  It doubles pretty easily, probably closer to triples.  So that seems good - but then I've read that to test if it's ready for baking one should do the float test (pinch out some starter and drop it into room temperature water - if it floats, it's ready, if not then it's not ready to bake.)  Mine consistently fails the float test.  So I googled a bit and am now more confused than ever - I turned up some results saying the float test doesn't apply to starter, but to levain.


So now I have two questions:

1) My understanding is that the starter IS the levain.  I feed it before bed, and the next day when it's close to its peak volume I can stir it all back together, take away my 80g discard as normal - but instead of discarding it I use it to bake with that day.  Am I mistaken here - is there an extra step I need to do in order to create a levain that's seperate?

2) Why is my starter failing the float test?  I'm assuming I should be testing the starter before I smoosh it all back together to near its original volume - I'd suppose the idea is to retain as much of the trapped air pockets as possible to allow it to float (so that thus, the float test is really just a test of how much air is present?)


Like I said, I'm new to this, so please let me know if my understanding is totally off on anything here.  I'm not just new to sourdough, but new to baking entirely - so I'm conducting lots of experiments at the moment (some of which even taste good!) ;)  Thanks!



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farinam's picture
farinam 2017 January 20

Hello Maxx,

The use of terminology is a bit fraught and different people use the same word in different ways.  Levain is just a french word that probably comes from the same latin root as levitate and means a rising agent (for bread).  In Italian, yeast is lievito.  Levain is often used to mean the stuff that you add to your flour and water to make the dough.  Other words that designate the same sort of thing but prepared a bit differently are 'biga' and 'poolish'.  On the other hand starter is often used to mean the stock of material that you use to 'start' your levain/biga/poolish.  But starter is also used in recipes to mean the same thing as levain.

In so far as the 'float' test goes, in my view, this is a waste of time and levain.  If it has risen to two or three times its original volume then it is well and truly ready.  If it is shot through with bubbles of gas and mousse like in appearance then it is well and truly ready.  But, if you really want to do a float test then you should not stir it down first because you need that gas to be still in there to make it lighter than water - just think polystyrene foam, if that wasn't full of gas it wouldn't float either.

Many people, once they have a good active starter keep it in the fridge.  Some time before they want to bake (often the evening before) they extract some from the container.  Sometimes this is as little as a spoonful, sometimes quite a bit and they feed it up to the amount that they need for their loaf with fresh flour and water.  This they leave out on the bench to become active.  The time required depends on the temperature and may be only a few hours if it is warm or it could be over night if it is cooler.  They also replace whatever they have removed from their starter with fresh flour and water and put it back in the fridge.  So there is no waste, no discarding, easy peasy. 

On the other hand, it is perfectly possible to go straight from your starter into the dough.  The main downside to this is that, if something bad has happened to your starter and it has died you might have wasted half a kilo of flour.  So, in essence, preparing your levain is equivalent to the instruction for bakers yeast to mix with some flour and water and leave aside until it bubbles which is purely to prove that the yeast is still viable and has nothing to do with an absolute requirement to make bread.

Good luck with your projects.


pplanders 2017 January 24


The float test is a measure of how active your starter is based on how much trapped CO2 is in it.

I feed my starter the night before I bake. I remove all but a tablespoon (soup spoon) and add 200 grams of flour and 200 grams of water. I mix it with my hands, cover it and leave it on the kitchen counter overnight. 

The next morning I take a teaspoon (I just use flatware, not measuring spoons) of it and gently place in about 8 oz (225 g) of 70-80 F (21-26 C) water in a measuring cup. Haven't had a problem with it floating.

I do NOT stir the starter or otherwise disturb it before the float test. If you are stirring yours or removing some and feeding it first, it will definitely sink like a rock.

Also, if you are not removing almost all of your starter when you feed it the night before it may also flunk.

For routine daily feedings, I remove about 80% of my starter and feed it with 8 oz of flour and 8 oz of water (mine is 100% hydration).

In my case flour = a 50:50 mixture of white bread flour and whole wheat flour.

First photo, after feeding last night. Second and third, this morning. Starter has doubled in volume and full of bubbles. If I let it sit on the counter without feeding it this morning, by this afternoon, the volume will have declined as its activity slows.




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