The Fresh Loaf

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Technical question about starter hydrations

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MissyErin's picture

Technical question about starter hydrations

I'm full of questions tonight, but this one has baffled my (mathematically trained) brain...

I keep a starter at 100% hydration.

For the ease of conversation, I'm going to refer to Maggie Glezer's recipe in Artisan Baking - Essential's Columbia.

The evening before baking it says to put together a firm starter, and mix with 63% water and 100% flour. The starter that its referring to in the book appears to be kept at about 30%.  (please double check me on this, as I'm still getting used to these hydration #s).  So, my technical question is this... to make this recipe, would I need to turn my 100% into a 30% first, then making it a 63% for this recipe?  OR, would I just turn my 100% into a 63%, and go from there.  What baffles me is that the 30 grams of starter that the recipe assumes I'm starting with is at 30%, versus my 100% should I just start from that point.  Granted, 30gms isn't much in relation to the 245gms that the remaining ingredients are, but does that affect the recipe much?  

I guess what I'm wondering is, will it take me 1 or 2 days to get to where I can actually start this recipe?  Meaning, how many refreshes would/should it take to get the starter where it needs to be in recipes such as this, that refer to a starter that is a different hydration than the one living in my fridge. and as future reference,  please let me know if I'm just being retardedly anal about this.. I understand.  My husband always emphasizes how LITERAL I am... so I would understand totally if that was the case here.  

And lastly, what are general % guidelines for a "stiff" starter versus a "wet" or "liquid" one.  Is it like 50% and up is wet and below is stiff?  Is it even as simple as that? My head is swimming!  and I'm sure yours is too after reading this ridiculous post! 

Thank you for help  :)


latida's picture


I have the same questions. In the past I have played with lot of calculations to make the transformation from wet to dry preferment. But ... you are right. In the end the change in overall hydration is pretty small.

So, tonight, two of my three preferments that call for a firm starter are being made with a 100% hydration starter. Sounds like science, right? Unfortunately, you won't be able to depend on my results as many of the loaves I loose sleep over don't end up with the open crumb I desire, despite my painstaking notes and calculations.

I'll let you know how it turns out.


bwraith's picture


The typical Glezer firm starter has a 60% hydration with a typical feeding schedule of something like 10g of starter fed with 30g of water and 50g of white flour. The 60% hydration refers to 30g of water being 60% of the 50g of flour in the starter. A hydration of 30% would be so dry I'm not sure you could even make it into a dough.

The easiest way to convert is probably to take a small portion of your liquid starter and feed it so that the hdyration is right for the recipe and let it rise and become ripe, then use it for the recipe as stated. For example, if you need 30g of 60% hydration starter, you could take 10g of your 100% starter and add 10g of water and 20g of flour, let it rise and peak. The water in the starter would be 15g, and the flour would be 25g for a 60% hydration and you would have 40g to work with, so you could scoop out your 30g and leave 10g sticking to the sides of the jar.

However, Greg is right that it won't make a lot of difference if you substitute that small amount of storage starter like 30g with your 100% hydration starter. By the way 100% hydration means you are feeding it with equal parts water and flour by weight, not volume. It should form a stirrable paste and rise by about 3x or so. If you are feeding equal parts by volume, then the starter will be a very thin batter and won't rise. It'll just foam and bubble in that case.

If you want to get fancy, you would ideally adjust the amount of your own starter you use so that the amount of fermented flour contributed to the recipe is the same. For example, the 30g of 60% hydration starter would have roughly 11g of water and 19g of flour in it, so you would want to use 38g of your 100% hydration starter, which would also have 19g of fermented flour in it. Then, you use 8g less water in the levain to compensate for the fact your 100% starter would have an extra 8g of water in it compared to the firm starter.