Why is Leaven not calculated in the Hydration Percentage?
First post with a quick question: why is the amount of leaven in a bread dough not considered part of the hydration percentage?
I'm working with a dough that is 800g Bread Flour, 200g Spelt, 500g water, that also has 800g Poolish (400g Bread Flour, 400g water, pinch yeast). I make the poolish the night before and then add it to the dough in the morning, but additional yeast is added to the dough so it doesn't really act like a leaven, per se. The Tartine charts show that they do not include the leaven in their calculation for hydration percentage. I'm trying to "think like a baker" and compare the hydration percentage of this dough vs. many others.
Calculating the Hydration Percentage based on Tartine, without factoring the Poolish, would be 50% (500g / 1000g). If I calculate with the poolish, then the Hydration percentage seems to be 64% (900g / 1400g). In reality I know that I'm only adding equal parts flour and water, but the arithmatic charges significantly.
What am I missing? This question seems so basic that I'm sure it is obvious. Thanks for the help.