The following three formulas are presented as a comparison of the results obtained when rye bread is made with a sourdough containing rye flour, with a sourdough containing white flour, and with no sourdough at all. Note that the first and second formulas are naturally leavened, and the only differences between them are that the first formula has a slightly higher hydration and it is leavened with rye sourdough, and a firm white levain leavens the second formula. The third formula relies on 1 percent yeast to leaven the bread. An experiment like this can be instrumental, as it is by no means uncommon for bakers who are unfamiliar with good rye principles to acidify either a portion of the white flour in a rye formula in lieu of rye, or to not acidify any flour at all. In fact, superior results are obtained only when all or a portion of the rye flour is acidified in rye breads: dough volume improves and crumb texture is more agreeable when comparing the rye sour-leavened bread to the white levain-generated. When no flour is acidified (the third formula), the crumb is gummy and unpalatable because the amylase enzymes had free rein during the bake, wreaking their expected havoc (for a discussion of the “starch attack.”) So while three formulas are included here, note that it is just the first, 65 Percent Sourdough Rye with Rye Sourdough, that I consider to represent the fullest potential; the second and third formulas in this series are resources that are included simply as a comparison to this first. A photo of the first two of the breads made with these formulas appears in the color insert.