Dough temperature is the single biggest variable in sourdough timing — and most recipes ignore it entirely. Crumb uses the actual science to give you an adaptive bake schedule based on your kitchen right now.
Calculate my bulk time →Work backwards from your target bake time to know exactly when to feed.
Using your starter at its peak — when it's most active and full of gas — is the single biggest factor in a successful bulk fermentation. Too early and fermentation drags. Too late and you've lost the strength you need.
The float test is widely cited but unreliable. Peak timing based on your starter's observed activity pattern is far more accurate.
Fermentation rate roughly doubles for every 10°F rise in dough temperature. This is the Q10 rule from food science — and it's why your 4-hour bulk on a warm day took 7 hours in winter.
When a recipe says "4–6 hours," that 2-hour window covers roughly a 10°F swing in kitchen temperature. Without knowing your actual dough temp, you're guessing inside a very wide range.
Doubling your starter percentage (from 10% to 20%) can cut bulk time by roughly 30–40%. Most bakers don't adjust starter % and temperature together — which is why results vary so much.
Hydration is just the ratio of water to flour — but the maths trips up a lot of new bakers. Enter your target loaf size and hydration and we'll work it out for you.
Firm dough that holds its shape and is easy to handle. Great for your first loaves. Less oven spring than higher hydrations but much easier to shape.
Where most home bakers land. Sticky enough to develop good gluten during folds, manageable enough to shape with practice. A reliable starting point.
Very open, irregular crumb if you can handle it. Requires confident shaping and good gluten development. Not recommended until you have 10+ loaves under your belt.
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