In a small bowl, cover raisins with 1-1/2 cups boiling water. Let stand while preparing bread; drain well. In bowl, dissolve yeast in 1/2 cup warm water.
In a large mixing bowl, place shortening, brown sugar, molasses, and salt. Add 2 cups boiling water; stir until shortening is melted. Add 2-1/2 cups of all-purpose flour. Beat with an electric mixer on low speed until combined, then medium speed 3 minutes or until smooth.
Gradually beat in yeast mixture until combined. Using a wooden spoon, stir in the drained raisins, rye flour and as much all-purpose flour as you can.
Turn out onto lightly floured surface. Knead in enough remaining all-purpose flour to make a moderately stiff dough thats smooth and elastic (6 to 8 minutes total). Shape into a ball. Place dough in a greased bowl, turning once to grease surface of the dough. Cover dough and let it rise in a warm place until its doubled in size (1-1/4 to 1-1/2 hours).
Punch the dough down. Turn out onto a lightly floured surface. Divide dough in half. Cover and let it rest for 10 minutes. Shape each half into a loaf and place in 2 greased 8x4x2-inch or 9x5x3-inch loaf pans or one in each size pan. Cover and let rise in warm place until nearly doubled (30 to 40 minutes).
Bake loaves in a 350 degree F oven for 45 to 50 minutes or until breads sound hollow when tapped with your fingers (if necessary, cover loaves loosely with foil the last 10 minutes of baking to prevent overbrowning). Remove breads from pans. Brush tops of warm loaves with softened butter. Cool breads on wire racks.