Why are you into it?
This is the one I'd text a friend about.
About
Every sourdough starter is a controlled biological system. Flour, water, wild yeast, bacteria. The ratio matters. The timing matters. The temperature matters. Get one wrong and you're feeding mold instead of building bread. King Arthur Baking walks through the basic ratios, but ratios are just the starting point.
Feed your starter at the same time every day. Not roughly the same time. The same time. Wild yeast operates on schedules tighter than most software deployments. Miss a feeding by four hours and the pH drops. The bacteria take over. You'll smell it before you see it. The Fresh Loaf forums document every failure mode in obsessive detail. Read them like debugging logs.
Discard before every feeding. This isn't waste, it's system maintenance. Old starter carries exhausted yeast and accumulated acids. Keep it around and you're asking the new flour to compensate for yesterday's mistakes. The San Francisco sourdough cultures that built reputations over decades understood this. They treated discard like clearing cache.
Room temperature works. Refrigeration slows everything down but doesn't stop it. Cold starter can go a week between feedings, sometimes two. But when you pull it out, it needs time to wake up. Three feedings minimum before it's ready for bread. Tartine Bakery built their business on starters that spent most of their time cold and came alive on command. Systems thinking applied to yeast management.
Fun fact
The oldest continuously maintained sourdough starter dates to 1889 and lives in a lab at King Arthur Baking, where it gets fed with the precision of a nuclear reactor.