Ok, I'm new to sourdough breads. So far I've made 4, 2 pure levain and 2 with 0.2% instant yeast added. The latter 2 worked perfectly, of the 2 pure ones, 1 was inedible and didn't rise at all, 1 was ok but a little flat and a little too sour. (The utter failure was Hamelman's Vermont Sourdough, the mostly ok one was Ken Forkish's Overnight Country Blonde, and then I made each with the added yeast.)
My starter is now 3 weeks old and reliably doubles in 4-5 hours at 70 F, which from what I understand seems pretty active. 3 days ago I switched it to 60% hydration from 100%, both the failures were at the higher hydration and while it bubbled nicey, I was worried it was too weak to rise and I thought it would be easier to see it rise with a stiffer dough. The 4-5 hour doubling is with the 60% hydration starter.
I feed it twice a day, usually discarding all but 60 g, then adding 38 g KA Bread flour and 22 g water. (Slightly less than 60%, but some more water gets in when I wet my hands to mix the starter, so I figure it about works out.)
On to the Tartine part and the question. I thought I would try the Tartine method since the others weren't working well for me. It's going right now, but not well. I notice that Forkish pre-ferments 12% of his flour in his levain build and uses 16.67% seed starter. His levain goes 7-9 hours at room temp before mixing the final dough. Hamelman ferments 15% of his flour in the levain, uses 20% seed starter in the levain, and ferments for 12-16 hours. Chad Robertson builds his leaven with merely a tablespoon of seed starter to 200 g flour, which works out to about 8% (I worked this out using Forkish's measurements; he says 216 g starter = 13 tablespoons, so about 16.6 grams per tbsp divided by 200 g flour), and Chad ferments only 7.5% of the flour for 4-6 hours at "moderate room temperature". A mere 150 g levain is meant to rise 1000 g flour, and for this bread 500 g cooked oat porridge as well.
Given that I've been having problems with rising using larger amounts of levain and longer fermentations, it seemed unlikely to work for me. But I did the levain and it took 9 hours to pass the float test, so longer than he suggests but it passed. The final dough has now been fermenting for 2 hours and 45 minutes. (3 hrs 30 min if you count the 45 minute autolyse which has the levain in it.) It has not budged at all that I can tell and I see no indication of fermentation, no bubbles, no sourdough type smells.
I've checked the dough temperature each time I do a stretch and fold and it's maintained a temp of 81-82 F. I'm not surprised that it hasn't perceptibly risen yet given the tiny amount of leaven, but clearly other people have success. So, anyone got some insight?