Make your own sourdough starter from scratch or check shopping Guide for sources.
Photo above: Sourdough Starter in large jar (the little bubbles show that it is active). The little jar has freshly ground spelt flour to feed the starter.
Below are ingredients, books and kitchen tools that can be used in this recipe and ordered from Amazon:
1 Cup fresh ground organic flour (Rye, Spelt, Kamut, Hard Red Wheat are best).
1 cup cold water (non-chlorinated and non-fluoridated)
Stir together the above ingredients, then place in a glass jar and cover securely with cotton cloth or cheese cloth and rubber band.
Place out doors in shady area among green plants if it is the warmer months or put on your kitchen counter is it is the cooler months. Take in at night and put on your kitchen counter. The next day, stir the mixture vigorously and either place back outside or keep on counter. Repeat this for 3 to 4 days. On day 4 you should notice small bubbles forming in the dough. On days 6, 7 and 8 add 2 tablespoons of flour. The dough will get thick and if it gets too thick then add a little water. On day 8, you should have a thick, bubbly dough that is ready to use. Place in a clean jar and put in the fridge.
How to keep starter:
Feed your starter a ratio of 1 cup of water and 1 ¼ cups of flour. You can feed the starter whenever you use some to replace what you used. If you do not use your starter regularly, try to feed it every 4 days. It can go up to two weeks without a feeding. You should get a clean glass jar for your starter every two weeks. Keep this starter in the fridge all the time. Always leave at least 1 cup of starter for next batch. I keep mine in a one gallon glass jar and when I get too much starter, I just make waffles, crepes or pancakes to use up the excess.
The photo above shows the starter with a little brown liquid on the top called "hooch". It forms when the starter has not been fed for a while and is not a problem. Just mix it in and feed the starter and the starter should get active again after a few feedings.