---
title: Starting a Sourdough Starter from Scratch
created: 2024-03-22 09:00
author: Amelia Fontaine
keywords: sourdough, starter, fermentation, bread, wild yeast
description: A complete seven-day guide to creating a sourdough starter from nothing but flour, water, and patience — with troubleshooting and the science of wild fermentation.
---

![Freshly baked bread](assets/images/bread.jpg)

# Starting a Sourdough Starter from Scratch

A sourdough starter is, at its most fundamental, a controlled environment for wild yeast and lactic acid bacteria. You are not adding anything to the flour and water except conditions — warmth, time, regular feeding. The microorganisms are already present on the grain, in the air, on your hands. Your job is to select for the ones you want.

This sounds mystical. It is actually chemistry. Lactic acid bacteria produce acids that lower the pH of the mixture, creating conditions that favour *Saccharomyces cerevisiae* (the yeast responsible for rise) and *Lactobacillus* species (responsible for flavour). By day seven, if conditions are right, you will have a stable, predictable culture you can use for the rest of your life.

## What You Need

- **Flour**: Wholegrain rye or wholemeal wheat is ideal for starting — higher in wild yeast and nutrients than white flour. Once established, you can switch to white.
- **Water**: Filtered or left to stand overnight if chlorinated. Chlorine inhibits fermentation.
- **A jar**: At least 500ml capacity. Glass is ideal so you can observe activity.
- **A scale**: Precision matters here. Volume measurements are unreliable.
- **Temperature**: 24–26°C is ideal. A kitchen counter in summer works. In winter, try near (not on) a warm appliance, or inside the oven with just the light on.

## The Seven-Day Guide

### Day 1 — Creating the Base

Combine 50g wholegrain rye flour with 50g room-temperature water in your jar. Mix thoroughly until no dry flour remains. Scrape down the sides, cover loosely (a cloth held with a rubber band, or a jar lid placed on top without sealing), and leave at room temperature.

Do nothing else today.

### Day 2 — First Signs

You may see small bubbles. You may see nothing. Both are normal. The mixture might smell slightly unpleasant — musty or even nail-polish-like. This is also normal; undesirable bacteria are colonising first before the yeast creates conditions that suppress them.

Discard all but 50g of the mixture. Add 50g rye flour and 50g water. Mix, cover, leave.

### Day 3 — Activity Increases

By now you should see more consistent bubbling. The smell may be getting more sour and less unpleasant. This is the lactic acid bacteria beginning to dominate.

Repeat the discard and feed: keep 50g, add 50g flour, 50g water.

### Day 4 — The Starter Wakes Up

You should now be seeing a predictable rise — the mixture expanding within a few hours of feeding before dropping back. Mark the level on the jar with a rubber band after feeding to track the rise. Aim for 50–100% increase at peak.

Switch to twice-daily feeding if your kitchen is above 24°C. Once daily is fine below that. Continue: 50g starter, 50g flour, 50g water.

### Day 5 — Transition to White Flour

If using rye to establish the culture, you can now transition: use 25g rye and 25g white bread flour for a couple of days, then move to all white bread flour if you prefer a milder flavour and lighter bread.

The starter should now smell pleasantly sour and yeasty, like a good craft beer. If it smells of cheese or acetone at this stage, it's too warm or not being fed frequently enough.

### Day 6 — The Float Test

A healthy, active starter will float when a small amount is dropped into a glass of water. Try this 4–6 hours after feeding, when the starter is at or near peak activity. If it floats, you're ready to bake.

If it sinks, continue feeding twice daily for another day or two. Patience.

### Day 7 — Ready

A starter that passes the float test and reliably doubles within 4–6 hours of feeding is ready to use. You have created a living culture that, with basic maintenance, can last indefinitely. Some bakeries use starters that are decades old.

## Ongoing Maintenance

**If baking daily**: Keep at room temperature, feed once or twice a day (same discard-and-feed routine).

**If baking occasionally**: Store in the refrigerator. Feed once a week. Remove from the fridge 12–24 hours before baking to bring it to room temperature and let it peak.

**The discard**: You discard starter each time you feed to prevent the jar from overflowing and to maintain a consistent ratio of culture to fresh flour. The discarded starter is excellent in pancakes, flatbreads, crackers, and waffles.

## Troubleshooting

**No activity after four days**: Make sure the water isn't chlorinated. Try a slightly warmer location. Use wholegrain flour.

**Pink or orange streaks**: These indicate contamination. Discard everything, sterilise the jar, start again.

**Liquid layer on top ("hooch")**: Grey-black liquid means the starter is hungry and hungry for longer than it should be. Pour it off and feed immediately; consider switching to twice-daily feeding.

**The smell**: Acetone/nail polish = too warm or too acidic; cheese = too cold; pleasantly sour and yeasty = correct.

## Why This Works

Wild yeast produces carbon dioxide (creating rise) and ethanol (which evaporates in baking). Lactic acid bacteria produce lactic and acetic acids, which contribute flavour and preservation. The ratio of these two acids depends on temperature and hydration: warmer and wetter conditions favour lactic acid (milder, yoghurt-like); cooler and stiffer conditions favour acetic acid (sharper, vinegar-like). This is why bakeries in different climates produce sourdough with distinct flavour profiles even from similar flour.

Your starter is genuinely local. The wild yeasts on your flour, in your kitchen air, on your hands — they are specific to your environment. A starter begun in Manchester will differ from one begun in Marseille. This is one of the things I find quietly extraordinary about bread.
