What is sourdough, exactly?

Sourdough is bread leavened by a natural culture of wild yeast and lactic-acid bacteria instead of commercial baker's yeast. That culture, called a starter, ferments the dough over hours, producing the rise, the tangy flavour, and the open crumb that define sourdough. No packaged yeast is used.

What does hydration mean in sourdough?

Hydration is the weight of water in a dough expressed as a percentage of the flour weight. A dough with 750g flour and 500g water is about 67% hydration. Higher hydration gives a wetter, stickier dough and a more open crumb; lower hydration is firmer and easier to handle. Most beginner recipes sit around 65–75%.

Why is my sourdough so dense and flat?

The most common cause is under-fermentation paired with a weak starter. Make sure the starter doubles reliably within 4–8 hours of feeding before you bake with it, give bulk fermentation enough time for the dough to look puffy and risen, and build strength with stretch-and-folds. Over-proofing can also cause a flat loaf, so judge the dough by feel rather than the clock.

Do I have to discard part of my starter every time I feed it?

When you are maintaining a starter at room temperature, yes — discarding keeps the culture from growing endlessly and keeps the ratio of fresh flour to old culture high enough to stay strong. You do not have to throw it away, though; discard can go into pancakes, crackers, and waffles. If you store the starter in the fridge and feed weekly, you discard far less often.

How long does it take to make a sourdough starter from scratch?

About 7 to 14 days. You mix flour and water and feed it daily; wild yeast and bacteria colonise it over the first week, and it becomes strong enough to leaven bread once it doubles predictably within hours of each feed. Cooler kitchens and whole-grain flours speed early activity, but reliable rising strength is what tells you it is ready, not the calendar.

What is bulk fermentation and how do I know when it is done?

Bulk fermentation is the first long rise, after mixing and before shaping, when the whole batch of dough ferments together. It is done when the dough has risen by roughly 30–75% (depending on your recipe and temperature), looks puffy and domed, shows bubbles on the surface and sides, and jiggles when you shake the bowl. Temperature drives the timing far more than the clock does.

Is sourdough healthier than regular bread?

Sourdough's long fermentation breaks down some of the starches and gluten and lowers the bread's glycaemic impact compared with fast-risen commercial bread, and the acids can make minerals more available. It is still bread, so it is not a low-carb food, but many people find naturally fermented sourdough easier to digest than standard loaves.

Sourdough Guide

Sourdough FAQ & Glossary: Common Questions and Terms Explained

Q: What is the difference between a starter and a levain?

A starter is the culture you keep alive and feed long-term — your mother culture. A levain is a separate, often larger build made from a spoonful of that starter specifically for one bake. Think of the starter as the source you maintain forever and the levain as the portion you grow fresh for a particular loaf, then use up entirely.

Plain-English answers to the most common sourdough questions, plus a glossary of the terms — starter, levain, hydration, bulk fermentation, autolyse — every baker needs to know.

Sourdough has its own vocabulary, and that vocabulary trips up almost every new baker. Recipes casually mention “levain,” “autolyse,” “bulk,” and “75% hydration” as if everyone already knows what they mean. This page is the plain-English reference: the questions people ask most, followed by a glossary of the terms you will meet again and again.

If you are just starting out, read the questions first to get the big picture, then keep the glossary handy as you work through your first few bakes.

The Big Picture: What Sourdough Actually Is

Sourdough is bread raised by a living culture instead of a packet of yeast. That culture — the starter — is a community of wild yeast and lactic-acid bacteria living in a simple mix of flour and water. The yeast produces gas that makes the dough rise; the bacteria produce acids that give sourdough its tang and help preserve the loaf.

Everything else in sourdough baking flows from that one idea. Because the culture works slowly, fermentation takes hours rather than minutes. Because it is alive, it needs feeding and responds to temperature. And because there is no standardised commercial yeast doing the work, you learn to read the dough rather than follow a stopwatch.

Frequently Asked Questions

What is the difference between a starter and a levain?

This is the single most common point of confusion. Your starter is the mother culture you keep alive indefinitely — you feed it, store it, and never use all of it. A levain is a fresh build you make from a small portion of that starter for one specific bake. You grow the levain to the size your recipe needs, let it ripen, and use the whole thing in the dough.

In practice, many home bakers blur the line and just call a peak-ripe starter their levain. If you want to size a build precisely for a recipe, the levain calculator does the math for you.

How much starter should I use, and at what ratio do I feed it?

The amount of starter in a dough is usually 10–20% of the flour weight — enough to leaven without making the loaf overly sour. When it comes to feeding, the feeding ratio describes the proportions of old starter to fresh flour to water, written as numbers like 1:1:1 or 1:5:5. A higher ratio (more fresh flour) takes longer to peak but builds a stronger, milder culture. The starter feeding ratio guide explains how to choose one, and the feeding calculator builds exactly the amount you need.

Why is my starter not rising?

A sluggish starter usually means it is young, cold, hungry, or fed at too low a ratio. Keep it warm (24–27°C is ideal), feed it consistently with fresh flour, and give it time — a new starter can take one to two weeks to find its strength. You are looking for it to reliably double within 4–8 hours of feeding. The guide to an active sourdough starter covers what healthy activity looks like and how to revive a slow one.

How do I know when bulk fermentation is finished?

Watch the dough, not the clock. Bulk fermentation is done when the dough has risen noticeably (roughly 30–75% depending on the recipe), looks puffy and domed, shows bubbles, and feels alive and jiggly. Temperature changes the timing dramatically — a warm kitchen can halve it. The bulk fermentation guide walks through reading the signs, and the bulk fermentation calculator estimates timing for your dough temperature.

Why is my bread dense, gummy, or flat?

These are the classic beginner problems and they almost always trace back to fermentation. Dense and flat usually means under-fermentation or a weak starter. Gummy crumb often means the loaf was sliced before it cooled or was slightly underbaked — check the internal temperature guide for the target finish temperature. A loaf that spreads and won’t hold its shape may be over-proofed or too high in hydration for your flour.

What does hydration mean and what should mine be?

Hydration is water weight as a percentage of flour weight. More water means a wetter, more open crumb but stickier, harder-to-handle dough. Beginners do best around 65–70%; once you are comfortable, you can push higher for a more open crumb. The hydration calculator keeps your flour and water in balance when you scale a recipe up or down.

Do I really have to discard starter every time?

While maintaining a starter at room temperature, discarding keeps it strong by keeping the proportion of fresh flour high. You don’t have to waste it — discard makes excellent pancakes, crackers, and waffles. Storing your starter in the fridge and feeding it weekly cuts way down on how much you discard. See the discard calculator to plan amounts.

Is sourdough actually healthier?

The long, slow fermentation predigests some of the starch and gluten and tends to lower the bread’s glycaemic impact compared with fast commercial loaves, and the acids can improve mineral availability. It is still bread and still carbohydrate-rich, but many people find genuine long-fermented sourdough gentler on digestion than standard supermarket bread.

Sourdough Glossary

Keep this list nearby while you bake. These are the terms that show up in nearly every recipe.

Starter (mother culture). The living mix of flour, water, wild yeast, and bacteria that leavens your bread. You feed and maintain it indefinitely. See active sourdough starter.

Levain. A fresh build of culture made from a portion of your starter for a single bake, grown to the size the recipe needs.

Feeding (refreshing). Adding fresh flour and water to the starter to renew its food supply. The proportions are the feeding ratio.

Discard. The portion of starter removed before feeding so the culture doesn’t grow endlessly. Usable in many recipes rather than thrown away.

Hydration. Water weight as a percentage of flour weight. Determines how wet and open the dough and crumb are.

Autolyse. A rest after mixing just flour and water (before adding starter and salt) that hydrates the flour and jump-starts gluten development.

Bulk fermentation (first rise). The long fermentation of the whole batch after mixing and before shaping, when most of the rise and flavour develop.

Stretch-and-fold. A gentle technique of stretching the dough up and folding it over itself during bulk fermentation to build gluten strength without kneading.

Shaping and pre-shaping. Forming the dough into a taut round or oval that holds structure. A light pre-shape rests the dough before the final shape. See how to shape sourdough.

Proofing (final proof). The last rise after shaping, before baking. Often done cold in the fridge.

Cold proof (cold retard). Proofing the shaped loaf in the fridge for 8–16 hours to deepen flavour and make the dough easier to score and bake.

Banneton. A cane or wood-pulp basket that supports the shaped loaf during its final proof and leaves the classic spiral pattern.

Oven spring. The rapid final rise a loaf gets in the first minutes of baking, before the crust sets.

Scoring. Slashing the top of the loaf with a blade just before baking so it can expand in a controlled way.

Crumb. The interior texture of the baked loaf — “open crumb” means large, irregular holes.

Over-proofing. Letting the dough ferment too long so it loses strength and rise. See over-proofed sourdough.

Float test. Dropping a spoonful of starter in water; if it floats, it is full of gas and likely ready to bake with.

Where to Go Next

If a term here sparked a question, the linked guides go deeper. Start with the active starter guide if your culture isn’t behaving, the bulk fermentation guide to learn to read the dough, and the no-knead recipe for a forgiving first bake. The calculators handle the arithmetic — hydration, feeding, and levain — so you can focus on the craft.

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