I learned how to make sourdough before I knew it was supposed to be difficult to capture a wild yeast. Since then, I've read all sorts of directions that include things like potato water, milk, sugar or commercial yeast. I suppose those things could work. But it seems to me that the simplest approach is the best. And at its simplest, all you need is flour, water, and a little time.
I've started sourdough cultures with white flour, whole wheat flour, rye flour, and spelt. I've also revived dried sourdoughs. Right now, I've got six cultures in my fridge, and the oldest is over ten years old. I don't consider myself a sourdough expert by any means, but I've got a decent amount of experience with the stuff.
When I'm starting a sourdough culture, I use roughly equal parts of water and flour in a clean jar. I like to use pint jars because they're easier to store in the fridge when they're not needed. I start with about a tablespoon of each of water and flour, and I stir it well. A little air in the mix seems to help it. I leave it on the counter, covered with a towel or cheesecloth. Whenever I pass by, I give it another little stir.
About twice a day, I add more flour and water, about the same amount with each feeding. I keep it fairly loose, about the thickness of pancake batter. After a day or two, bubbles start forming, and I start changing the water/flour ratio so it's a thicker mix, more like a thick cake batter. Soon, it gets to the point where it doubles in size in the jar in an hour or so. I keep feeding until the jar is threatening to overflow when it has doubled.
At that point, I take most of the culture out of the jar and use that to make the first loaf of bread. I add flour and water to the remaining culture, and feed it as before until the jar is about 1/4 full when it's just been stirred and it's at its low point. Then I add extra flour so it's a thicker mixture, like a cookie dough, and I cover the jar and put the jar into the fridge. The way I figure, the extra flour will be a good enough feeding to sustain it while it goes to sleep in the cold. So far, it has worked well.
I've been lucky in that the water where we live has been fine straight from the tap for the sourdough. But if you live in an area where the water is heavily chlorinated or you use a water softener, you might need to use filtered or bottled water to get the culture started.
If the culture is bubbling well and you've got a lot accumulated, but it's not quite strong enough, you don't have to throw it away.Just add it to a regular bread recipe with commercial yeast. It will add a little flavor, and you won't be wasting it.
And that's it. Flour and water and time. No need for extra ingredients, no need for throwing away pints of not-quite-ready sourdough culture every time you feed it.
One thing to keep in mind is that sourdough cultures from different areas will result in different breads. That's why I keep so many cultures. Some are more lively, some are more sour. Crusts and textures are different. You can influence the outcome by the way you handle the dough, but the cultures themselves still play a big role. And that's part of what makes sourdoughs so interesting.
