Combine water, rye flour and yeast. Sour 2-3 hours in a warm place. Add remaining water, shortening, and salt. Knead 7-10 minutes, let rise until double. Punch down and shape into 2 round loaves, score tops (3 slits with straight edge knife) and let rise again.
Bake at 375', 30 minutes. May take a bit longer. Will not be really browned.