Calculate the exact flour and water amounts for feeding your sourdough starter at any ratio. Get estimated peak times so you know when your starter is ready to bake.
The feeding ratio determines how much fresh flour and water you add relative to the amount of existing starter you keep. A 1:1:1 ratio (equal parts starter, flour, and water by weight) doubles the starter volume and ferments quickly, usually peaking in 4 to 6 hours at room temperature. A 1:3:3 ratio dilutes the starter more, slowing fermentation to 8 to 10 hours. A 1:5:5 ratio creates a very slow rise of 12 to 16 hours, ideal for overnight levains or when you cannot tend the starter for a while. Choosing the right ratio lets you time your baking schedule precisely.
Ambient temperature is the other major factor controlling fermentation speed. At 21 degrees Celsius, a 1:1:1 feeding peaks in roughly 4 to 6 hours. At 26 degrees, the same feeding can peak in just 3 hours. At 18 degrees, it may take 8 hours or more. Our calculator estimates peak times based on your chosen ratio and a standard room temperature of 22 degrees Celsius. If your kitchen is warmer, expect a faster peak. If cooler, expect a slower one. Placing the starter near a warm oven or inside a proofing box can speed things up when needed.
A well-maintained starter should roughly double in volume between feedings and have a pleasant, tangy aroma. Signs of trouble include a strong acetone or nail-polish smell (too much acetic acid from under-feeding), a thin hooch layer of liquid on top (starter is hungry), or sluggish rising. To revive a neglected starter, feed it with a 1:2:2 ratio twice daily for 3 to 5 days. Use unbleached flour, as bleaching removes some of the nutrients wild yeast and bacteria need. Whole wheat or rye flour added at 10 to 20% of the total flour provides extra minerals that boost fermentation.
Source: https://www.kingarthurbaking.com/learn/guides/sourdough
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