Debugging Tartine Bread

Recipe for the uninitiated: Tartine Country Loaf. The book is more detailed.

I used to live 2 blocks from Tartine in the Mission of SF. A year ago we moved to the East Bay to seek a more, let's say, conducive atmosphere for our daughter to grow up in. But I missed having easy access to good bread! That is what got me started down this dark path.

I gotta say, this journey has been rough. Many times I would think I'd figured it out, only to then have a bad loaf and not understand what I did wrong. Things just seemed highly unpredictable. I watched tons of YouTube, read this forum, read the Sourdough Journey, the Bread Code, the Tartine book, Flour Water Salt Yeast, you get it. There was a lot of frustration, but I am an obsessive person by nature and I couldn't stop trying to figure it out. At one point I was baking 3 batches a week to speed up my understanding of what was/wasn't working. I've easily baked > 100 batches in the last year.

A lot of advice was really hard to parse. I texted with an award-winning baker in Berkeley and tried to get help on internet forums (including this one), but it was really hard to figure out which variables were off or which piece of advice was right. Was it my starter? Was it my bulk fermentation time? Was the levain just not active enough when I started the dough? Was I just too rough with shaping? Changing one thing seemed to have an effect, but then it would stop for some reason, and I wasn't sure whether to keep the change, revert the change, or change it again.

I've finally been able to consistently produce that bottom loaf. No bad loaves anymore. And these two things nailed it for me:

Using way more than the recommended amount of starter in the levain. Like, 30-45 grams of starter. I think this is the true key that unlocked way better loaves. If you remember anything from this, it's to just use more starter in your levain!
Starting with 98-100 degree water for bulk fermentation (our house is about 70 degrees). Because the levain was at ~70 degrees, it would bring water temp down a ton when mixed in. Then, fermantalyse inside the mixing bowl would bring the temp down even more.

Just those two things have made it so I get a consistent loaf in 3.5 to 4.5 hours of bulk fermentation.

Things that didn't work:

Letting bulk fermentation go on much longer, like 6-8 hours (since I was getting underfermented loaves). For some reason this just produced weird loaves that would exhibit characteristics of under fermentation (caverns), but would also be impossible to work with like an over fermented loaf (ie the gluten had broken down and they were weirdly sticky and wet)
Feeding my starter every 12 hours (or more). This just sucked, was a huge hassle, felt wasteful, and didn't meaningfully matter in my experience. Goal was to get it super active, and I guess that worked, but it was so much overhead. Super annoying.
Doing it by hand instead of using a KitchenAid mixer. I got some advice that maybe this was breaking down the gluten formation too much after fermantalyse. Didn't seem to matter, that said I got in the habit of doing it by hand after fermantalyse because of that debugging journey.
Being super gentle with the dough, especially toward the end of bulk fermentation and shaping. I actually can't say this did nothing, but the loaves were so inconsistent that this was like the equivalent of buying $300 running shoes when you just took up the hobby. It's not what's going to really move the needle at that level.

In hindsight, I think some of the variability I was getting was due to a combination of starter activeness and the amount of starter I was mixing into the leavin. I just had no idea those were the key things. I also, especially in the beginning, just used a 'tablespoon', as described in the book. But, I wasn't careful about measuring that out and I assume would get 'lucky' occasionally when putting in more starter and get a better loaf.

Otherwise, I pretty much stick to the recipe as described. Here is what I do:

Starter Maintenance:

House is ~70 degrees Fahrenheit.
50g water, 50g 1:1 bread flour/wheat flour combo every 24 hours, always feed in the morning. Dump everything but 2 or so tablespoons of starter, maybe 30g.

Making Levain:

Mix 30-45g of starter (depending on how active it seems to be) with 200g 1:1 bread flour/wheat mixture and 200g of 78-80 degree water.
Wait 12 hours

Making dough:

Turn the oven light on (this brings the oven temp up to around 83-84 degrees, which is a nice temp to bulk ferment at).
Mix levain and flour/water in KitchenAid stand mixer. Use 98-102 degree water. Mix for a couple minutes on setting 2.
Wait 30 minutes for fermantalyse to happen.
Mix in 20g of Salt with 50g of 90-100 degree water (this seems to matter less, I've used 82 degree water and it was fine, but you're just looking to maintain temp). I now use my hands, but I'm pretty confident you could use a stand mixer with a dough hook with no ill results.
At this point the dough is often around 82 degrees, maybe 84. In my experience it will keep dropping.
Put the dough in a Cambro container, then put it in the warm oven to maintain temp
Do the stretch & folds like normal every 30 minutes
After 3.5 to 4.5 hours, it should be doming. On the Cambro, sometimes the dough will show as being at or above the 2 liter line, but not always. As long as it's doming, it seems good in my experience.
Shape into rounds, wait 30 min
Shape into loaves and drop into bannetons.

Overnight Retard:

I throw a tea towel over top the bannetons and toss in the fridge for what usually ends up being ~17 hours (I start the dough process in the morning and end by around 3pm). I've also used saran wrap to not develop a 'skin', but the effects of this don't seem meaningful to me. I often bake one loaf, then wait another 2 days to bake the other one. It's still great! The fridge seems to do more than slow it down, it seems to basically stop fermentation in my experience. Maybe my fridge is on the colder side.

Baking:

Place a cookie sheet in the bottom rack to prevent the bottom of the dutch oven from getting too hot and burning the loaf
Set oven to 500 and wait for it to get to temp
Pull out the dutch oven, rice flour the bottom and toss in the loaf direct from the fridge. The coldness of the loaf makes no difference in my experience to letting it sit out while the oven pre-heats. It's also easier to cut with a razer when it's cold.
Score the loaf at a 45 degree angle to get that nice lip
Bring oven temp to 470 and bake for 20 minutes lid on
Take lid off dutch oven and bake for another 30 minutes

I hope this helps someone who was as frustrated as I was, and helps them get a bit less lost. Just use more starter in your levain!