The Fresh Loaf

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starter hydration maths question.

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JOHN01473's picture
JOHN01473

starter hydration maths question.

i have worked through all the maths lessons and i still seem to have a problem
where the maths of starters / sponges / poolish / biga are concerned.
here is what i mean.

i take 10g of starter @60%
so how much is flour and how much is water?

i add 20g water and 20g flour.
total weight is now 50g.
what it the hydration now?

i add a further 6g of water and 24g of flour.
total weight is now 80g.
what it the hydration now?

what i need to see is how much water and flour is totaled up for each calculation.

mwilson's picture
mwilson

First I would question whether it's really necessary to build your starter in this way. Seems bizarre / random to me with no real reasoning unless you can explain otherwise.

In the case of just flour and water where hydration is known, calculate like this... For example a dough @ 60% hydration you have a total of 160% (added 100% represents flour). 160% in decimal = 1.6. So 10g dived by 1.6 = 6.25. So of the 10g 6.25 is flour and the remaining 3.75 is water.

JOHN01473's picture
JOHN01473

i was given the build plan and i have been using it for a while successfully.
i just wanted to check the maths.
from what you said i have come up with this.

do you think the maths now works out right and the hydration levels are correct?

cranbo's picture
cranbo

yes this is correct. 

the hydration % of your dough at any time is:

( TW / TF ) * 100

where TW is the total amount of water in your dough, and TF is the total amount of flour in your dough.

JOHN01473's picture
JOHN01473

thanks.

i plan to give your Sourdough recipe for beginners a try.

John

cranbo's picture
cranbo

Happy to help. Let me know how it turns out!