In a clean bowl, mix 250 grams light wheat flour and 250 grams wholegrain wheat flour. For best results, use freshly ground wholegrain flour. If desired, you can just skip the light wheat flour and only use wholegrain flour. If you have a wheat intolerance, just use spelt or rye. For a gluten-free version of your sourdough, you should get it started on rye flour and later re-train it by feeding it rice, corn, or millet.
Now add lukewarm water to your flour mix until you get a viscous pulp. Cover the bowl with a clean towel or linen, and place it in a location where it can remain undisturbed at constant room temperature (about 65-72° F/ 18-22° C). Stir the starter once a day, preferably using a wooden spoon.
After two to three days you will notice that your sourdough has started to develop that typical sour, acidic smell, and you may see bubbles on the surface.
If three days have passed and there's no activity, give it one more day; maybe it's just a bit slow to start. If a dark crust develops on the surface, just mix it in with the rest of the starter; nothing to worry about.
If your starter is doing what it is supposed to do, you now know that lactic acid bacteria as well as yeasts have made their home there, both bringing the desired microbial balance into your starter. This is the original and most basic method of making a sourdough, called "spontaneous fermentation."
How do you know if your sourdough starter is a success? Just trust your eyes and your nose. If you see colors like red or green, black or blue, if it smells really bad or if mold starts growing, you can be reasonably assured that your starter has turned for the worse. The same is true for a strong vinegary smell. The starter went off in the wrong direction, and you should discard it.
Just try again until it works. It usually does, but if you think you need a little extra help, then you should get a ready-made sourdough culture. You might have to look around a bit, but stores with a good selection of natural and organic items often carry it in their inventory. Just "inject" it into your flour-and-water mix. It'll get your starter going in the right direction by helping it develop the proper balance of microbes.
Now that you have a bubbling, stable starter with a pleasantly leavened smell, you can go ahead and prepare for the first "feeding."
"The Breadhacker - Unleash The Sourdough" by Ilka Beier
Baking bread is very simple. All you need are 4 basic ingredients: Flour, water, salt and sourdough. I'll show you a simple method for making a tasty homemade bread in any kitchen oven. Each step, from cultivating and maintaining a sourdough, all the way to baking the bread, is documented in easy to follow videos, embedded within the book.
Go to http://www.thebreadhacker.com/ and follow the links to download our enhanced iBook from the iTunes iBook store, or download a pdf version from the "shop" section of our website directly.