Pour warm water into a large mixing bowl.
Sprinkle yeast over water; stir until dissolved.
Add shortening, salt, sugar, and 1 1/2 cups flour.
Beat 2 minutes at medium speed of an electric mixer or 300 vigorous strokes by hand.
Scrape sides and bottom of bowl frequently.
Stir in remaining flour and beat with a spoon until smooth, about 1 to 1 1/2 minutes.
Scrape batter from sides of bowl.
Cover dough with a clean cloth and let rise in a warm place, free from draft, until doubled in bulk, about 30 minutes.
When batter has risen, stir down by beating about 25 strokes.
Spread batter evenly in a greased 9x5x3-inch loaf pan.
Batter will be sticky.
Let rise in warm place, free from draft, until edge of batter reaches 1/4 inch from top of pan, about 40 minutes.
Bake in moderate oven (375°F.) for 45 to 50 minutes, or until brown.
When done, immediately remove from pan.
Brush top with melted margarine or butter.
Cool.