using firm starter in liquid/batter starter formula


I am brand new to this forum and it has been several years since I made a sourdough. I have recently started reading about it again, and have a renewed interest and understanding of sourdough. My question is this...

I was reading Maggie Glezer's Artisan Baking Across America and have decided to try out the firm starter she describes. I calculate this out to be a 50% hydration starter. It seems most of the formulas I come across are using 100% hydration starters and was wondering how to do the conversion.

Do I just increase the water and decrease the flour used in the recipe? Or do I reduce the amount of starter and add extra water? In my mind, either would work. But I wonder if reducing the amount of starter would also increase the fermentation time.

Also, I was looking at her conversion process to go from batter-type sourdough starter into a firm one and I think her math is off. She says to mix:

Liquid starter: 0.5 oz (15 grams) - 30%
Water: 0.5 oz (15 grams) - 30%
Unbleached bread flour: 1.8 oz (50 grams) - 100%

Assuming a 100% hydration on the liquid stater, wouldn't that yield a 39% hydration starter? I thought perhaps she was reffering to those that use equal volumes (rather than weights) of flour and water for their starters. This is probably closer to about 150% hydration I think. But even using this high of a number, I come up with a 43% hydration starter.

On that note, I also notice that she actually refreshes the 50% starter at a 60% rate for some reason. So eventually it would be 60%. I think she does that to make measuring in grams easier. Would the 10% make a big difference in the later loaves?

Sorry for the long post, but my renewed interest has created more desire to really understand the whole thing.

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Millciti's picture
Millciti 2009 March 27

I have Maggie's book from the library but seem to have missplaced it. I was going to write you but keep forgetting to check. I think that she may be using a starter that was at about a 110-120% hydration. If the pictures show a foamy top it is probably more than 100% hydration. My best suggestion for really getting into percentages is to buy a grams scale. I ordered one from Amazon it was only about $20-25 dollars U.S. Then you can measure everything by weight, which is much more efficient than cups. Although there are some out there with formulas using measurement by cups that you can find. I would still caution you that this is problematic if you use different types of flours. Most flours have a different weight per cup up to 15-25g difference depending on the type and grind. In my Food Science class we all measured out 3 cups of normal flour and weighed them, out of 20 students we only had 4-5 weights close enough to consider a match.

So to obtain a starter that is a specific percentage of hydration - you would measure out about a tsp of your starter into a new container. Add equal weights of water and flour for 100%. Add 2 times the flour as the water for 50% hydration 1.5 times the flour for 75% and so on. Start with about 15-25g of water to the correct percentage of flour. Refresh it once or twice doubling the amount till you have enough starter for your recipe, and you should be good to go. Some bugs like more moisture than others but they will adjust in a few cycles to the new accomodations.

For most recipes using a firm starter at 60-70% hydration seems to work well, if you keep in mind that 70% is the hydration level for most doughs.

Hope this helps sorry it has taken so long for someone to give you an answer. This has been a very busy semester for me. I am so looking forward to summer for more time to bake.


SourdoughBaker 2009 April 25

Hi Terri,
I love that particular book - but I have found that sometimes it's a bit technical for practical purposes.
Having run starters commercially for 20 years, I think sometimes people get caught into the details, and it does seem quite complex when you read it back. There are a few tricks though, I admit. Acid / alkali balance seems to sum it up in a nutshell, but doesn't help when it comes to figuring stuff out!
Anyway, have a look at my website '' for a whole lot of stuff about different kinds of starter techniques. Look up 'old dough starter technique' and you'll see some articles about thicker starters and why they are so easy to work with from a domestic point of view.
Hope this helps!

Graham's picture
Graham 2009 April 26

Maverick I think that lower hydration leavens (final brew, added to dough) have gained in popularity in Australia over the last 10 years. A 50% hydration mix breaks down as it ferments and when ripe is quite fluid. Stiffer leavens are perceived to ferment more slowly, be more stable and potentially contain more nutrient and therefore yeast/bacteria, than a 100% hydration leaven on a similar feed cycle.

Slower fermentation is partly due to a less fluid environment for transporting yeast, bacteria and nutrient, as well as (perhaps) the tendency for stiff ferment bakers to hold their leavens at lower temperatures.

We are often told by baking technologists that stiff and cold environments favour acetic acid production over lactic acid production. But not all cool-raised doughs, made with stiff and/or cool starters/leavens, are overly fruity (acetic) to taste.

I used to use only 100% hydration and now its usually 50% -75%. The lower hydration is well suited to bakers who feed their leavens only once in 24 hours...and keep their leaven at room temperature for some or even all (depends on temp) of this period....a very common practice in Australia.

bobku 2011 September 22

So how would you use a 50% hydrated starter in a recipe that calls for a %100 hydrated starter. I want to make bread as sour as possible. As stated above "Do I just increase the water and decrease the flour used in the recipe? Or do I reduce the amount of starter and add extra water? In my mind, either would work. But I wonder if reducing the amount of starter would also increase the fermentation time." Keeping in mind i want a more sour dough.

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