Understanding sourdough hydration for open crumb

Why hydration changes the crumb

Hydration is the weight of water divided by the weight of flour, expressed as a percentage. A dough made with 500g flour and 350g water is 70% hydration. That number matters because water transforms flour into an extensible, fermentable mass. More water means more steam during baking, softer gluten, and a greater chance of large, irregular holes. But an open crumb is not simply a high-hydration trophy. It is the result of flour strength, fermentation, dough handling, shaping tension, and heat. Push water too high without the right flour or technique, and you get a slack, sticky dough that bakes flat and gummy rather than airy.

Flour first: heritage grains and thirst

Before you chase 85% hydration, look at your flour. Heritage grains behave differently from modern strong white bread flour. British-grown heritage wheats, spelt, emmer, einkorn, and older wheat populations often carry more flavour and character, but their gluten is usually weaker and more extensible. Wholemeal and freshly milled flours also absorb more water because bran and germ soak it up, yet those same particles can cut through gluten networks and make the dough less elastic.

• Strong white bread flour: higher gluten, tolerates 75–80% hydration with good folding.
• Wholemeal heritage wheat: thirsty, often needs 5–10% extra water, but mix gently and avoid over-developing.
• Spelt: extensible and fragile; 65–70% is a sensible starting point.
• Einkorn: low gluten strength; 60–65% is often plenty for a home loaf.
• Emmer and khorasan: robust flavour and moderate gluten; try 68–75% depending on how much wholemeal is in the mix.

If you blend heritage flour with strong white, you get the best of both: flavour from the old grain, structure from the modern one. A common starting ratio is 70% strong white and 30% heritage wholemeal.

Reading the dough, not just the numbers

Recipes are maps, not laws. A dough that feels perfect in a cool kitchen on a dry day may become soupy in a warm, humid one. Start at 70% hydration if you are new to sourdough. Use 20% mature starter and 2% salt based on flour weight. If you keep a 100% hydration starter, remember that 100g of starter adds roughly 50g flour and 50g water, which shifts your true hydration.

After mixing, wait 20 minutes before judging. Flour needs time to hydrate. If the dough still feels tight and lumpy, add water 10g at a time. If it is slack and spreadable, resist the urge to dump in flour. Give it a set of folds and see how it tightens. Aim for a dough temperature of 24–26°C. Warmer dough ferments faster and becomes more extensible; cooler dough is slower and easier to handle.

Technique that makes higher hydration manageable

Water is only useful if you can shape the dough. The following approach helps high-hydration dough hold its structure without fighting it.

• Autolyse: mix flour and water only, then rest for 30–60 minutes before adding starter and salt.
• Fold, don’t knead: use wet hands and perform four sets of coil folds or stretch-and-folds, spaced 30 minutes apart.
• Build tension: pre-shape lightly, rest 20 minutes, then shape with a bench knife and a light dusting of flour.
• Cold prove: place the shaped dough in a banneton and retard for 8–16 hours in the fridge. Cold firms the dough and deepens flavour.

If the dough sticks, wet your hands rather than adding flour. If it tears, you have gone too far. Stop, rest, and fold more gently next time.

Proving, baking and the crumb you actually get

Bulk fermentation matters as much as hydration. Let the dough rise until it is 20–30% larger, with a domed edge, visible bubbles, and a slightly sweet, yoghurt-like smell. Underproofed dough bakes with tight gumminess and a few giant tunnels. Overproofed dough spreads, bakes pale, and turns dense. For a home oven, preheat a Dutch oven at 250°C. Bake with the lid on for 20 minutes, then remove the lid, drop to 230°C, and bake for another 20–25 minutes until deep brown. The internal temperature should reach around 96–98°C. Cool completely for at least two hours before slicing; cutting early smears the crumb and makes good bread seem gummy.

A practical path to a more open loaf

Choose one heritage flour and keep the rest of your recipe steady. Try 70% hydration, 20% starter, and 2% salt. Autolyse, fold gently, and watch the dough rather than the clock. If the loaf holds its shape well and the crumb is slightly tight, increase water by 5% next time. If shaping feels like wrestling a wet pillow, reduce by 5%. Keep notes on flour, water, room temperature, and timings.

Open crumb is a lovely thing, but it is not the only measure of good bread. Heritage grains bring nutty, earthy, sometimes honeyed flavours, and they often make a loaf that is more nourishing and more interesting than a uniform white one. Learn the dough in front of you, and the holes will follow.