Hydration is the most important variable in sourdough bread making, and the one most likely to trip up beginners. A 65% hydration dough is manageable and forgiving. An 80% hydration dough is a wet, sticky mess that requires a completely different technique. Understanding hydration — and how to work with whatever hydration level your recipe calls for — is essential to making consistent, high-quality sourdough.
What Hydration Actually Means
Hydration is expressed as a percentage: the weight of water divided by the weight of flour, multiplied by 100. A dough with 500g flour and 350g water has a hydration of 70%. Note that this is flour weight, not total ingredients — the salt and any other ingredients are not included in the calculation. This is baker's percentage, the standard way professional bakers express recipes.
Different hydration levels produce very different results: 60-65% produces a tight, dense crumb suitable for burger buns and sandwich bread. 65-72% produces a moderate, versatile crumb. 72-80% produces an open, artisan-style crumb with large holes. 80%+ produces extremely wet doughs (like focaccia) that require specific handling techniques.
Why Hydration Matters for Sourdough
Sourdough fermentation produces acid (lactic and acetic acid from the bacteria), which weakens the gluten network over time. This is why sourdough has a more complex flavor than commercial yeast bread — the long fermentation produces more acid, which develops flavor. But the same acid that develops flavor also weakens gluten, which means high-hydration sourdough requires more developed gluten to support the wetter, heavier dough.
This is the central tension of high-hydration sourdough: you need a strong gluten network to support the wet dough, but the fermentation is constantly working to break that network down. The solution is either to limit fermentation time (use a young, active starter) or to develop gluten through stretch and fold rather than kneading.
Adjusting for Different Flours
Not all flours behave the same at the same hydration. Whole wheat and rye flours absorb significantly more water than white flour — up to 25% more for whole wheat. If you're making a 70% hydration whole wheat dough, you're actually closer to 55% effective hydration on the white flour portion. This is why whole wheat breads often feel denser — the effective hydration is lower even though the nominal hydration is the same.
When substituting whole wheat for white flour, start with 5-10% higher nominal hydration than you would for white flour, then adjust based on how the dough feels. The dough should be tacky but not sticky, extensible but not slack.
Working with High Hydration
High-hydration doughs (above 75%) are notoriously difficult to work with because they're sticky and seem to resist shaping. The key insight: don't fight the stickiness. Use wet hands (constantly dipping in water), use a bench scraper, and don't add flour to reduce stickiness — the flour changes the hydration of the outer dough layer and can make the loaf denser.
For shaping high-hydration doughs, use the coil fold technique during bulk fermentation. This builds structure gently without deflating the dough. During shaping, use a gentle touch — the dough should be handled minimally, with the goal of creating surface tension rather than compressing the dough.