Why the crumb opens
An open crumb isn't luck. It's gas, and the gas is a record of how the dough was fermented — which is why you can read a loaf by its holes.
People ask for an open crumb as if it were a decoration you add at the end. It isn’t. The holes are gas, and the gas got there because a wild culture spent a long time eating the flour and breathing out carbon dioxide. The crumb is the fossil of that process. You can read a loaf backwards from it.
The gas has to be made, then held
Two things have to go right. First the culture has to produce enough gas — that’s fermentation, and it’s slow on purpose. Then the dough has to hold that gas without tearing — that’s the gluten, built by folding rather than by machine.
If you rush the first, there’s no gas to hold and the crumb is tight. If you neglect the second, the gas escapes and the loaf goes flat. An open crumb sits in the narrow window where a strong, extensible dough meets a fully-fermented one.
Reading the holes
- Small, even holes mean a young dough, or one kept cold — not wrong, just early. Our rye is like this on purpose.
- Large, glossy holes mean a long, warm proof and a high hydration. That gloss is gelatinised starch, set by steam in the first minutes of the bake.
- A dense streak at the base usually means the loaf went into the oven under-proofed and the crumb collapsed before it set.
None of this is mystical. It’s why every ticket at the counter lists the hydration and the fermentation time — those two numbers, more than the flour, decide the holes.
What we actually do
Every sourdough here gets eighteen to twenty-four hours, most of it cold. The cold slows the yeast but not the bacteria, so the loaf keeps developing flavour while it holds its shape. We fold rather than knead, four times in the first two hours, and then we leave it alone. Fermentation doesn’t take instruction.
Come Saturday, cut a slice and hold it to the window. If you can see daylight through it, that’s eighteen hours of doing very little, on purpose.