1. Rinse beans and pick through to make sure they are clean. Soak beans overnight in a non-reactive pot or bowl on the countertop in about 10 cups of water mixed with the 2 1/2 tablespoons of salt. The salt will help to soften the skins on the beans so they cook better.
2. In a pot large enough to hold the beans, boil 4 quarts of water with 1 t baking soda. Drain the beans and add to the pot once water is boiling. When it returns to a boil, continue to cook for 15 minutes. The beans will develop a foam so keep a close eye on the pot as this can boil over. The foam won't hurt anything but you can skim it if you want. The beans should be tender but do not overcook. When you blow on the beans the skin should peal back easily. Once done, drain the beans in a colander and rinse lightly.
3. While the beans are boiling, add molasses, brown sugar, ginger, mustard, salt, pepper and cayenne to a bowl and mix. Boil 3 cups water to be ready when the beans are done.
4. If you are using salt pork, add 1 piece of the salt pork to the bottom of the bean pot. Add 1/2 the the beans and then add another piece of the salt pork. Add the remaining beans. If you are not using the salt pork just add the beans to the pot. Pour the ingredients from the bowl over the beans in the bean pot. Rinse the bowl with a little of the boiling water to get all the good stuff and add to the beans. Add enough boiling water to just cover beans and if you are using the salt pork, top with the remaining piece of salt pork.The water should just cover the beans, not drown them. You can always add more water if necessary but too much water can be a problem.
5. Cover the bean pot and place in a cold oven. Bake, covered at 250 °F for 7 1/2 hours. Check the pot at about 5 hours and if it looks really dry add boiling water to come just below the top of the beans. Do not over add water. After 7 1/2 hours, remove the bean pot top and continue cooking for 30 to 45 minutes or until the beans are at the desired consistency. Let the beans set for at least 30 minutes before serving.
6. Another time I was cooking beans I checked them at 4 1/2 hours and this time they needed a little water. The pictures of the pot before the water was added and after the water was added are below. It took 1/4 to 1/2 c at most to bring the water just to the surface. At this stage of the cooking you don't want the water above the beans. Again, do not add too much water.
7. When they are done they will be deep brown without the sight of any water on top. Before serving give them a quick stir.