For 1 tablespoon baking powder, mix 2 teaspoons cream of tartar with 1 teaspoon baking soda (add 1 teaspoon cornstarch if you're making a big batch; it prevents the mixture from caking ...

and the other with 1/2 teaspoon of baking powder. Pour about 15 mL (1 tablespoon) of warm water into two empty cups. Add 1 drop of detergent solution to the water in each cup and gently swirl to mix.

I did a search of online recipes and the most consistent response was that usually you use between 1 to 2 teaspoons of baking powder per 1 cup (150g) of flour. From a scientific point of view ...