Why Hydration Changes Everything in Sourdough (The Science Behind Wet vs Stiff Dough)

⏱ 7 min read

Spring has a funny effect on my baking. The kitchen is warmer, the starter is bouncing back with more energy after months of sluggish winter feeds, and I start getting ambitious again. New bakes, wetter doughs, more experiments. And that usually means I end up thinking a lot about hydration.

If you have spent any time in sourdough circles, you will have heard people throwing around percentages like "I bake at 75%" or "my porridge loaf hits 85% hydration." It sounds almost technical, a bit intimidating even. But once you understand what hydration is actually doing to your dough at a physical and chemical level, it stops being a number and starts being a tool. A genuinely useful one.

What Hydration Actually Means

Hydration in baking is expressed as a percentage of water relative to flour, by weight. So if you use 500g of flour and 375g of water, you are baking at 75% hydration. Simple enough. But what changes when you nudge that number up or down is where it gets interesting.

Flour absorbs water and that water activates two key proteins , glutenin and gliadin , which combine to form gluten. The more water you add, the more these proteins can move around and link up. A stiffer dough (say 65%) has tighter, more compact gluten networks. A wetter dough (80%+) has gluten that is more extensible, more mobile, and behaves very differently under your hands.

How Water Affects the Crumb

This is the bit most people are actually chasing when they go high hydration: that open, custardy crumb with large, uneven holes that looks stunning on a slice. The science behind it comes down to gas retention and dough extensibility.

During fermentation, your sourdough culture produces carbon dioxide. The gluten network traps those gas bubbles, and as the dough expands and bakes, those bubbles set into the crumb structure you see in the finished loaf. In a wetter dough, the gluten strands are more extensible, meaning they can stretch further around larger gas pockets without tearing. That is how you get bigger, more dramatic holes.

In a stiffer dough, the gluten is stronger but less stretchy, so gas pockets tend to be smaller and more evenly distributed. That gives you a tighter, more uniform crumb , which is actually ideal for certain breads. A sandwich loaf at 68% hydration is a pleasure to slice and butter. A ciabatta at 80%+ is a different beast entirely, with that characteristic irregular hole structure and slightly chewy texture.

Neither is wrong. They are just different tools for different jobs.

What Hydration Does to Fermentation

Here is something that does not get talked about enough: water is not just a structural ingredient, it is also an environment. And your sourdough culture lives in that environment.

A wetter dough creates more mobility for the yeast and bacteria in your starter. The wild yeast and lactic acid bacteria can move more freely through the dough, which means fermentation activity can be more vigorous. Enzyme activity also ramps up in higher hydration environments, which affects how quickly starches break down and how much sugar is available for the microorganisms to feed on.

This is particularly relevant in spring, when ambient temperatures start creeping up and your starter is already more active than it has been for months. A high-hydration dough in a warm kitchen can move faster than you expect. I have lost count of the number of times I have started a bulk ferment on a Friday evening with some music on, got a bit distracted, and come back to find the dough has gone further than planned. You learn to pay attention, especially as the seasons shift.

The Crust Story

Hydration plays a role in crust development too, though it is a bit more nuanced. A higher hydration dough produces more steam inside the loaf during baking, which keeps the surface supple for longer. That extended oven spring means the crust can expand fully before it sets. The result tends to be a thinner, crispier crust with better bloom on the scoring.

Lower hydration doughs produce less internal steam, so the surface sets more quickly. That gives you a thicker, more robust crust, which has its place. Some people actually prefer it, especially in enriched doughs or anything baked at a lower temperature.

If you are making sourdough pizza or flatbreads, hydration choices matter just as much. A pizza dough around 65 to 68% is easier to stretch and holds its shape on the peel, while something at 72 to 75% gives you a more open, airy base with a better char. The DoughRise Pizza Making Kit is brilliant for this kind of experimentation because you have everything in one place to actually test the differences across a few sessions without improvising your setup each time.

Flour Matters More Than You Think

One thing that trips people up: hydration percentages are not universal. A 75% hydration dough made with a strong bread flour (12 to 13% protein) will behave very differently from the same ratio made with a weaker plain flour or a whole grain flour.

Whole wheat and rye flours absorb significantly more water than white flour because the bran particles soak it up. So a loaf with 20% rye at 75% hydration will feel stiffer than a white loaf at the same percentage. If you are adding whole grains to your bakes this spring (and it is a great time to experiment with lighter, more flavourful loaves), you may find you need to push hydration up a bit to get the dough feeling right.

Think of it like debugging something in code: if the output is not what you expected, look at what changed in the inputs. Different flour is a different variable, and it affects everything downstream.

Where to Start if You Are Experimenting

If you are fairly new to higher hydration baking, 72 to 75% is a genuinely good place to start. It is wet enough to give you an interesting open crumb without being so slack that it turns into a handling nightmare. From there, build your technique: stretch and folds during bulk fermentation become more important at higher hydrations because they build the gluten structure the dough needs to hold itself together.

Once you feel confident there, you can start pushing higher. Each percentage point above 78% asks a bit more of your technique, but also rewards you with something noticeably different in the finished loaf.

Spring is actually a decent time to experiment with this. Your starter is lively, your kitchen is at a more stable temperature than January, and there is something satisfying about using the longer evenings to actually learn what your dough is doing rather than just following a recipe and hoping for the best.

Happy baking! Find everything you need at doughrise.store

Photo by Ben Lei on Unsplash