This one starts with a little commercial yeast to give it a head start. If you don't have yeast, simply use the flour and water. Whole wheat or rye flour will work better for the non-yeast method. You'll have to feed the non-yeast starter longer to get to the "sour" stage (7-10 days vs. 3-5 days).
1cupall purpose flour, unbleached all purpose flour is recommended. (You can use whole wheat or rye flour)
1/2cuproom temperature water, un-chlorinated water is best
1tspyeast
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Equipment
a large at least 1 quart glass jar or similar sized glass container,
Instructions
Stir well so there are no lumps or dry flour is visible. Cover the top of the jar loosely with a piece of plastic wrap or paper towel.
Let stand at room temperature for 24 hours.
Feeding procedure to be done every day:
Stir your starter well. Discard (throw out) 1/2 cup of the starter mixture. Add to the jar, 1 cup flour and 1/2 cup room temperature water. Stir well. Cover and let stand at room temperature for 24 hours.
Repeat this daily feeding until mixture is nice and bubbly and develops a pleasant "sour" smell. That should take 3-5 days starting with yeast or 7-10 days with just flour and water.
Once you reach that point, cover and refrigerate your starter, using and/or feeding it in the same manner every 7 days or so, except let it stand at room temperature after feeding for several hours, before returning to the refrigerator.
Notes
You now have what's known as a 100% Hydration Sourdough Starter. That simply means that your starter has water (hydration) in equal amounts to the flour.BUT WAIT! How can it be equal if we're adding a cup of flour and only a 1/2 cup of water?? Because it's BY WEIGHT!! (1 cup flour weighs 4 oz and 1/2 cup water weighs 4 oz). Took me a minute to wrap my head around that, too :)Fact is though, depending on how you measure, your cup of flour probably isn't 4 oz exactly. It might be as much as 4 1/2 oz in reality. Which brings me to another suggestion and that is to move away from cups to ounces if you have a kitchen scale. It's both easier and more precise. (See my Tips section for more on that.)