Brothh

What it means

A sourdough starter is a self-sustaining colony of wild yeast (primarily Saccharomyces species) and lactic-acid bacteria (Lactobacillus) living in a flour-and-water paste. The yeast leavens the bread; the bacteria produce the acid that gives sourdough its tang and extends shelf life.

A healthy starter doubles within 4-8 hours of feeding at 70-75°F. Feeding ratios (starter : flour : water) control the rate: 1:1:1 peaks in ~4 hr, 1:5:5 in ~10 hr. Most bakers keep a 100% hydration starter (equal parts flour and water by weight).

Examples

Daily feed (on counter)

Discard all but 50g, feed 50g flour + 50g water (1:1:1)

Fridge hold (1x weekly)

Feed before refrigerating; warm + 2 feeds before baking

Do

Use unchlorinated water — chlorine kills the culture.
Use whole grain or a rye/whole-wheat mix to boost activity.

Don't

Feed with cold flour from the fridge — it slows fermentation.
Expect peak activity on a starter under 2 weeks old.

Related terms

Baker's Percentage

Every ingredient in a bread recipe expressed as a percent of flour weight. Flour is always 100%. Water 65-75%, salt ~2%, levain 15%.

Calculators that use this

Sourdough Starter Feeding

Compute flour, water, and ripe time for any starter feed ratio and target hydration.

Dough Hydration

Baker percentage math for flour, water, salt, and levain — get the ratios right every bake.

Yeast Converter

Convert between active dry, instant, and fresh yeast — with baker’s percentage when you give flour weight.