Sourdough Crumb Chart: A Visual Guide to Fermentation
This crumb chart tracks how a single dough develops during bulk fermentation - from just mixed to over eight hours in. Each loaf was shaped and baked at a different stage, and the cross-sections show exactly how time, fermentation, and structure affect the final result.
Below, you'll find a 3×3 grid of the crumb, followed by detailed notes on what’s happening inside the dough at each hour - written by Pump Street's Understanding Sourdough workshop teacher, David Wright.
Note: The loaves were all made from the exact same dough. Flour was 80% Strong White, 20% Wholemeal. Hydration 70%. Inoculation 30%. Dough temp 25 degrees. Baked in a cast iron Lodge Pan, 250C.
SOURDOUGH CRUMB CHART
A Closer Look At What's Happening to the Sourdough Crumb Structure During Fermentation at Each Hour:
Hour 0
Baked straight after mixing, whilst the dough contains sourdough starter the fresh flour hasn't been given any time to ferment. The result is a completely inedible loaf, like a sod of heavy clay.
Hour 1
After an hour of bulk fermentation, the dough has started to develop. The crumb is noticeably more open but there's a big divide between the solid base and flying crust.
Hour 2
The dough is still very much underdeveloped, the crumb is irregular and the bread has baked into a pyramid shape. The extremely large alveoli (holes) are not from good fermentation but where the crumb has separated during the bake.
Hour 3
The volume of the loaf has improved and the shape indicates a much better development. Again there is an uneven crumb, but some people like this kind of look. The alveoli are slightly stretched which shows it is still slightly underdeveloped.
Hour 4
The alveoli are less stretched and the loaf has a more relaxed look about it, the crumb is still uneven with one particularly large hole. Definitely in the ballpark of good fermentation but at the lower margin.
Hour 5
Great volume, a mixed crumb but not too much difference between the largest and smallest alveoli. This loaf demonstrates good fermentation.
Hour 6
Again here we have an example of good fermentation, a mixed crumb with some slightly larger holes. The volume has fallen off slightly, the dough was getting fragile at the point of baking.
Hour 7
The volume has dropped again but the crumb is very even, as the acids of fermentation soften the gluten structure the holes get smaller but there's still plenty of gas to leaven a pleasing loaf.
Hour 8
We can see the crumb getting tighter and the volume decreasing as we head into over-fermentation. The dough was very very fragile before baking and hard to score. Still very edible though!
Interested in Learning More?
Join us at a Pump Street Sourdough Workshop.
Spend the day with David learning how to shape, ferment, and bake in our dedicated workshop space just down the road from the bakery in Orford. You’ll leave with fresh loaves, a jar of starter, and the confidence to bake at home.