☞ TESTER TIP: Occasionally the yeast normally present in whole grains fail to establish itself in a new culture; if, after 3 or 4 days, the culture darkens, develops a mold, or smells bad, dump the whole batch and start over. After a week, the culture, or sourdough starter, will be ready to use or to be stored refrigerated in an airtight container for a couple days. [Editor's Note: If storing the sourdough starter for more than a couple days, you'll need to maintain it, which we explain how to do just below.]
☞ TESTER TIP: The most important point to remember at the early stages is to feed the sourdough starter daily. Even when it shows no apparent fermentation, the yeast is busy multiplying and consuming nutrients at a very high rate. By the second or third day, it will swell, show bubbles, and give off a clean sour smell. Over the next few days the activity will become more and more vigorous and the smell more intense.