On each of my last two posts about bulk fermentation, I talked about pulling at your dough to see how it feels and pulling a window to see how your gluten is developing. There’s one more thing that you should do before each fold and before you do either of the two things above.
Look at your dough. And remember how it looks before each fold. Compare these images with each other. Your dough changes every time subtly.
How smooth and shiny is it? Are you seeing any bubbles around the edges of the dough or on top? Has it flattened back out completely? If you look in the corners, is it starting to dome a bit: meaning instead of just a gloppy edge, is it holding its shape and curving up? Can you still see the remnants of your last fold: meaning it didn’t smooth and flatten out completely?
Once I start seeing some doming and bubbles and some of the last fold, I usually give it one last fold. All these signs tell me how strong my dough is. You want your dough to be strong so that it can hold it’s shape during the next steps. I find it’s around 6 hours if I use 20% leaven, keep my dough at 73-75F, and the ambient temperature in my kitchen is 73-75F too.