Getting Started with Sourdough: How to Make a Starter From Scratch

2. Day 1: Mix Flour and Water

A sourdough starter requires a one-to-one ratio of the two ingredients based on weight. Use 50 grams of flour and 50g of room temperature water. It's important to measure your ingredients in weight rather than volume to get an accurate one-to-one ratio. If you don't have a kitchen scale, use 1/4 cup of water and a scant 1/2 cup of flour. Stir together thoroughly, preferably with a wooden spoon. Keep in a roomy container at room temperature (70°F) for 24 hours. The cooler the temperature, the longer it will take for your starter to develop.