In large bowl, combine yeast and warm water; stir to dissolve yeast.
Stir in 2 cups of the all-purpose flour, the whole wheat and rye flours, caraway seed, salt and molasses; beat until smooth.
Stir in enough of the remaining all-purpose flour to make dough easy to handle.
Turn out onto lightly floured surface.
Knead 10 minutes or until dough is smooth and elastic, adding as much remaining flour as needed to prevent sticking.
Shape dough into ball.
Place in large, greased bowl; turn dough once to grease surface.
Cover with towel; let rise in warm place (85 °F) until doubled, about 1 hour.
Punch dough down; divide into 4 equal pieces.
Shape each piece into ball; place each into greased 2-pound coffee can.
Cover; let rise in warm place until doubled, about 45 minutes.
Bake in preheated 375 °F oven 35 to 45 minutes or until loaves are browned and sound hollow when tapped.
Remove from cans to wire racks.
Brush tops of hot loaves with butter; cool completely.