In a bowl, dissolve yeast in 1/4 cup water. Add sugar, molasses, shortening, salt and remaining water; stir well. Add rye flour; beat until smooth. Add enough all-purpose flour to form a soft dough.
Turn onto a floured surface; knead until smooth and elastic, 6-8 minutes. Place in a greased bowl, turning once to grease top. Cover and let rise in a warm place until doubled, about 1-1/2 hours. Punch dough down.
Shape into 4 round loaves. Place on greased baking sheets. Cover and let rise until doubled, 45-60 minutes. Bake at 350° until golden brown, 30-35 minutes. Brush with butter.