Brining Beans with Baking Soda
from https://www.seriouseats.com/

Transforming a hard, dried bean into one that's tender, creamy, and enjoyable to eat requires first that the bean absorbs water and then, as it's heated, the bean's physical structure needs to change. The bean's seed coat presents an initial obstacle; the water must first penetrate the seed coat before the interior of the bean can begin to absorb water and cook.

Once water is able to penetrate the seed coat and heat is applied, the pectin that sits inside begins to transform. As the pectin heats up it transforms from a hard, insoluble substance that holds the cells together into a soft, water-soluble material. As that pectin sitting between the cells softens and dissolves in water, the cells begin to fall apart, and that loss in structural integrity is what makes cooked beans soft and creamy.

If you brine hard-to-cook beans before cooking them, they will cook faster and have a better final texture, and, in addition, they will have greater nutrient availability. Using a brining solution with an excess amount of sodium by adding both salt and baking soda produced the best results in texture, and reduced the cooking time significantly for both black and kidney beans (the two beans tested). For kidney beans and other hard-to-cook beans, the author strongly recommends brining them in a salt and baking soda solution.

For perfectly cooked, creamy beans, use the following ingredients and volumes:

3 tablespoons (36g) Diamond Crystal kosher salt; for table salt, use about half as much by volume or the same weight
1 3/4 teaspoons (10g) baking soda
8 1/2 cups (2L) water
1 pound (455g) dried beans, picked of any debris and rinsed

In a large bowl, cover beans with 8 1/2 cups (2L) water. Add salt and baking soda, stirring briefly to combine, then cover loosely and let soak at room temperature at least 8 and up to 12 hours (AI says 12 - 24 hours). Do not add acidic ingredients like tomatoes, vinegar, or citrus until the beans are fully soft, as acid keeps them hard. Cook until tender.