Drain beans, reserving liquid. Return beans to Dutch oven. Add pork, celery, onion and salt. Combine 3 cups reserved bean liquid with molasses, ketchup, dry mustard, pepper and brown sugar in a large saucepan. Bring to a boil; pour over beans; cover Dutch oven. Bake in a very slow oven (225 degrees) for 10 to 12 hours, until beans are tender. Thirty minutes before serving, increase oven temperature to 375 degrees. Uncover beans; bake 30 minutes or until liquid has almost evaporated. Makes 8 servings.