I’ve been using my own Sourdough starter for the past few years. It’s actually the third one that I’ve created out of the ether in a magical process that is detailed on the Serious Eats:Slice website:
Information on making and using your own sourdough starter >>
A-ha! That’s your secret! Now I can make my own damn sourdough starter instead of begging for a bit of yours. I’m pulling myself up by my own yeasty bootstraps now, Buddy-boy…
One thing to remember though…. each one is somewhat different. My current one is both tasty and springy.