Calculate exact feeding amounts for any starter quantity, ratio, and hydration level.
The feeding ratio tells you how much flour and water to add relative to the amount of starter you keep. A 1:1:1 ratio means equal parts by weight: 50g starter + 50g flour + 50g water. A 1:3:3 ratio means 50g starter + 150g flour + 150g water. Higher ratios give the yeast and bacteria more food, which produces a slower, more controlled fermentation with a milder flavor. Lower ratios ferment faster and produce more acidic, tangy results.
For daily maintenance, 1:1:1 works well. For building a levain the night before baking, 1:2:2 or 1:3:3 gives you a longer, more predictable peak that's easier to time with your baking schedule. If you're going away for a day or two and can't feed, a 1:5:5 ratio with refrigeration can sustain your starter for 2-3 days without getting overly acidic.
Hydration is the ratio of water to flour, expressed as a percentage. At 100% hydration (the most common), you use equal weights of flour and water, producing a thick batter-like consistency. At 80% hydration, the starter is stiffer and rises more dramatically. At 65% hydration, you get a stiff levain that holds its shape, which some bakers prefer for specific bread recipes.
Higher hydration starters ferment slightly faster because water helps enzymes break down starches more efficiently. Lower hydration starters develop more complex flavors and are easier to assess visually because the rise is more pronounced and the peak is more obvious.
Starting a sourdough culture from scratch takes 5-14 days. Mix 50g whole wheat or rye flour with 50g lukewarm water in a jar. Leave it loosely covered at room temperature (70-78 degrees F). Every 24 hours, discard all but 50g and feed with 50g flour and 50g water. By days 3-5, you'll see bubbles forming. By days 7-14, the starter should reliably double in volume within 4-8 hours of feeding.
The first few days can smell unpleasant (vinegary, cheesy, or even like nail polish remover). This is normal. Undesirable bacteria dominate early on but are gradually outcompeted by the lactobacillus and wild yeast you want. Don't give up if days 3-5 look inactive. A lull is normal before the right organisms establish themselves.
Whole wheat and rye flour work better for starting a culture than white flour because they contain more wild yeast and bacteria on the grain surface, plus more nutrients to feed them. Once your starter is established and reliably active, you can switch to all-purpose flour for maintenance if you prefer.
Room temperature maintenance means feeding every 12-24 hours. This is ideal if you bake frequently (3+ times per week). Refrigerator storage slows fermentation to a crawl, meaning you only need to feed once a week. Pull the starter out the night before baking, feed it, let it peak at room temperature, and use it the next morning.
For longer storage (vacations, breaks), you can dry your starter: spread a thin layer on parchment paper, let it dry completely at room temperature, then crumble and store in an airtight container. Dried starter can be revived months or even years later by rehydrating and feeding for a few days.
Starter isn't rising: The most common cause is temperature. Sourdough fermentation slows dramatically below 70 degrees F and nearly stops below 60 degrees F. Find a warmer spot: on top of the refrigerator, inside the oven with the light on (but not the heat), or in a cabinet near an exterior wall that gets warm. Ideal fermentation temperature is 75-80 degrees F. If temperature isn't the issue, try switching to whole wheat or rye flour for a few feedings, as they contain more wild yeast and nutrients.
Hooch (dark liquid on top): This is alcohol produced by the yeast when it runs out of food. It's harmless. You can stir it back in (for more tang) or pour it off (for milder flavor). Hooch means your starter is hungry and needs more frequent feeding or a higher ratio.
Smells like acetone or nail polish remover: This indicates excessive acetic acid production, usually from going too long between feedings. Increase feeding frequency to every 12 hours for a few days, and use a higher ratio (1:3:3) to give the yeast more food relative to the bacteria. The smell should normalize within 2-3 feedings.
All-purpose white flour produces a mild, predictable starter with consistent behavior. Whole wheat flour creates a more vigorous, faster-rising starter with a more complex flavor because it retains the bran and germ, which contain more nutrients and wild yeast. Rye flour is the most active option and produces the tangiest flavor. Many bakers maintain their starter with all-purpose for convenience but feed with whole wheat or rye for 1-2 feedings before baking to boost activity.
Bread flour (higher protein) produces a slightly different texture in the starter but works identically for maintenance. Bleached flour should be avoided because the bleaching process can kill wild yeast. Organic flour isn't strictly necessary but may contain more diverse microorganisms since it hasn't been treated with pesticides that could inhibit fermentation.