Brian Smith of Lincolnton, North Carolina has made more overproofed loaves than underproofed ones. He is confident this is true for most home sourdough bakers, even though the internet spends far more time warning people about underproofing. The reason is simple: underproofing looks dramatic and is easy to identify, so it gets photographed and discussed. Overproofing produces a loaf that looks fine until you cut into it, which is why so many people bake it, serve it, and never quite figure out what went wrong.
He is not saying this to correct the internet. He is saying it because it took him about eighteen months to understand which mistake he was making, and the sooner someone else figures it out, the sooner their bread improves.
What Overproofing Actually Looks Like
An overproofed loaf, when cut open, has a dense, gummy crumb — not the kind of dense that suggests the bread needs more hydration, but a flat, uneven density where the large bubbles have collapsed and merged. The structure that bulk fermentation built gets destroyed in the final proof if you let it go too long. The gluten network weakens. The yeast exhausts itself. What goes into the oven is dough that has already done most of its work and has nowhere to go when the heat hits it.
The crust of an overproofed loaf often looks fine. It may even look good — blistered and golden, with a reasonable score. This is why the mistake is so easy to miss. You look at the crust and think you did everything right. Then you slice it and find the interior is not what you wanted.
Why Bakers Get Impatient at the Wrong Time
Smith’s theory — and it is a theory built on 200 logged batches, not a scientific study — is that most home bakers get impatient during bulk fermentation, where waiting longer is usually correct, and then get complacent during the final proof, where they assume the fridge or the timer is managing the process for them.
Bulk fermentation feels slow. Nothing dramatic is happening. You poke the dough and it bounces back. You look at it and it has risen some, but maybe not as much as a recipe described. It is tempting to move on. Smith used to move on too early in bulk fermentation for the first year of baking — he would shape before the dough was genuinely ready because he wanted to get to the next step.
The final proof, on the other hand, happens in the refrigerator and is easy to ignore. You put the shaped loaf in the fridge, close the door, and go to bed or go to work. It feels finished even though it is still happening. The conventional wisdom is that a cold retard — overnight in the fridge — is hard to overdo. This is mostly true, but “mostly” is doing real work in that sentence. At certain hydration levels, in certain refrigerator temperatures, even a cold retard can go too far if you leave it long enough.
How Tracking Temperature Fixed the Problem
The fix, for Smith, was the notebook. Once he started recording ambient temperature alongside bulk fermentation times, the pattern became clear within a few weeks: his summer bulk fermentation windows were consistently shorter than his winter ones, sometimes by an hour or more, because the kitchen was warmer. He had been applying winter timing to summer conditions — which is how he had been overproofing without knowing it.
He now checks the kitchen temperature before starting a bake and adjusts the expected bulk fermentation window accordingly. In July, when his kitchen runs around 78 to 80 degrees Fahrenheit, he starts checking the dough at three and a half hours. In January, when the kitchen drops to 68 or 70, he might not check until the five-hour mark. The recipe has not changed. The formula has not changed. Only the timing adjusts, based on what the temperature tells him the dough is doing.
He would not have figured this out without the notebook. He is sure of that. The pattern is too gradual to hold in memory across seasons. You need the entries side by side to see it, and the spiral notebook is what makes that possible.
Understanding fermentation timing is the core skill in sourdough — read more in Fermentation Has a Schedule. It’s Not Yours. and see how Smith tracks it all in his baking notebook. More at About Brian Smith Lincolnton.