In a large crock, holding at least 3 quarts, add yeast mixed with water. Add sugar and flour, beat to mix. Cover, let rise until light and slightly aged, 24-48 hours. Starter may be kept in refrigerator for 7-10 days without attention. Then, it should be stirred and equal amounts of flour and water added. To keep starter, pour off amount needed for recipe, then add flour and water to remaining mix. Amount will depend on amount of starter that is left.