I’m not sure where I heard this or who said it, but cooking is art and baking is chemistry. There is a lot of truth to this statement. There is a wide margin of error in measurements for cooking—depending on what you are cooking of course. Baking on the other hand is precise. The recipe must be studied and followed as if it were the Talmud. Perhaps this is why my mother was a much better cook than baker because she hated to follow recipes.
Two of the most common ingredients in baking, and ones which most of us give little thought about, are baking soda and baking powder. And while they have similar names, they are used in different circumstances.
Baking powder and baking soda are leavening agents, making breads and other baked goods “rise.” They work in the same way yeast does by producing carbon dioxide. Baking powder and baking soda produce carbon dioxide when water is mixed with an alkali and an acid.
Baking powder is mixture of an alkali (base)—sodium bicarbonate (i.e., baking soda)—and an acid (calcium acid phosphate, sodium aluminum sulfate or cream of tartar).
There are two types of baking powder: single-acting or double-acting. With single-acting baking powder, you need to work fast because it makes carbon dioxide as soon as the recipe is mixed. With double-acting baking powder, sit down have a cocktail because it produces those little bubbles as the recipe is heated in the oven. For obvious reasons, most baking powder is double acting.
You can make your own baking powder. Just take a ½ teaspoon of cream of tartar and ¼ teaspoon of baking soda if keeping longer, add ¼ teaspoon of corn starch to absorb moisture.
Baking soda is pure sodium bicarbonate. While baking powder has its acidic element built in, baking soda works when it is combined with moisture and an acidic ingredient in the mixture (e.g., yogurt, chocolate, lemon, buttermilk, or honey). This is why you will find baking soda in recipes that call for acidic ingredients, like lemon, chocolate, or green apples.Because this reaction begins immediately, you need to bake recipes which call for baking soda immediately.
Finally, you should keep in mind that you can substitute baking powder in place of baking soda, though it will require that you use more of it and it could affect the taste. But it doesn’t work the other way around—you cannot use baking soda when a recipe calls for baking powder. Baking soda by itself lacks the acidity to make a cake rise.
So, there you have it! Mystery explained. Now go back a cake and don't forget to follow that recipe to the T!