Mix the water, sugar and yeast until dissolved. Beat in the flour until the batter is smooth. Pour into a clean 2 qt. jar and cover with a cloth. Let stand at room temp. for 2 to 3 days or until starter has a sharp, almost winy odor and is bubbly (it will be full of lively bubbles after a short time and will continue to bubble, more sedately, until it is sufficiently sour). Exact times can't be given, as weather and temp affect the rate of fermentation.
TO USE: If not used at once, cover the starter with a lid and refrigerate it. It will be lively enough to use for about 18 hrs; if refrigerated longer, "feed" it lightly and let it become bubbly at room temp - usually letting it stand overnight - before using it.
This tangy batter is the key ingredient of English Muffins and many other sourdough breads. This recipe makes 3 cups enough to make a large batch of muffins, with enough left over to serve as a nucleus for a future baking. The starter keeps well in a covered jar in the refrigerator so long as it is "fed" with a small amount of flour and an equal amount of water about every 2 weeks - this keeps the yeasts alive. Or freeze it for indefinite storage. To revive it, feed it after it thaws and let it stand at room temperature until bubbly enough to use. If liquid gathers on the surface of stored starter, stir it in before adding flour and water. Your starter will be good so long as it responds to feeding and has a pleasantly odor. If neglected, it may develop a pink or greenish tinge and an unpleasant odor. If that should happen, start over. To increase a small amount of leftover starter to a quantity large enough for a baking, add flour and water in equal quantities, but never exceed the proportion of a cup of flour to a cup of starter. Let the mix ferment, lightly covered, at room temp until very bubbly; then, if you need still more starter, add more flour and water and ferment again.