Using colander or sieve, rinse baked beans. Discard any that are discoloured.
In a large heavy bottomed Dutch oven or pot, cover beans with 9 cups of water.
Bring to boil over medium-high heat; reduce heat to medium and boil gently for 3 minutes.
Remove from heat; cover and let stand for 1 hour, then drain.
Return beans to pot with 12 cups of water.
Bring to boil over medium-high heat. Reduce heat to medium and simmer, covered for 45 minutes (beans should be tender).
Remove 2 cups of the cooking liquid and set aside.
Drain beans.
Slice bacon into six pieces and cook over medium-high heat in frying pan. Do not cook until its crispy. This is simply rendering the fat from the bacon.
In a dutch oven or 16-cup casserole dish, combine beans, 2 cups of reserved cooking liquid, tomatoes, bacon, onions, ketchup, molasses, sugar, dry mustard and salt and pepper.
Bake, covered in a 300°F oven for 2 and a ½ hours.
Uncover and bake for another 1 and ½ hours or until desired thickness of sauce is reached.
